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  • Ruby on Rails form_remote_tag missing template

    - by Donald Hughes
    I'm using form_remote_tag(:url => {:controller => "home", :action => "search"}, :update => "mydiv"). When I click submit on the form "mydiv" is populated with the error "Template is missing. Missing template home/search.erb in view path app/views". I've tried multiple render options in def search, but they all result in the same error. It looks like the search method is trying to use it's default render even though I'm specifying what I want. I've tried: render 'index' render :text => 'Return this from my method!' Is my url incorrect? Is it not submitting back to my home controller's search method?

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  • backbone marionette - displaying a view in a layout region which has already been rendered

    - by Justin Wyllie
    I have something like this: //render the layout Layout.layout = new Layout.Screen(); MyApp.SomeRegion.show(Layout.layout); //render a view into it var mView = new CompositeView({collection: data}); Layout.layout.SomeRegion.show(mView); That all works fine. The layout has 3 regions. The above has rendered a view into one of them. Now, later, I want (in response to some user interaction) to render another view into one of the other regions. So I try: var mView2 = new CompositeView({collection: data}); Layout.layout.SomeOtherRegion.show(mView); But 'SomeOtherRegion' no longer exists on Layout.layout. I looked at this in Firebug. In the first case Layout.layout has my three regions defined on it. In the second case, not. Though they are still there in the regions object. This is the same layout instance. It looks like once a layout has been rendered you cannot render into it again? There must be a way. Nb. I don't want to re-render the layout. I hope that makes sense --Justin Wyllie

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  • Multi-part template issue with Jinja2

    - by Alan Harris-Reid
    Hi, When creating templates I typically have 3 separate parts (header, body, footer) which I combine to pass a singe string to the web-server (CherryPy in this case). My first approach is as follows... from jinja2 import Environment, FileSystemLoader env = Environment(loader=FileSystemLoader('')) tmpl = env.get_template('Body.html') page_body = tmpl.render() tmpl = env.get_template('Header.html') page_header = tmpl.render() tmpl = env.get_template('Footer.html') page_footer = tmpl.render() page_code = page_header + page_body + page_footer but this contains repetitious code, so my next approach is... def render_template(html_file): from jinja2 import Environment, FileSystemLoader env = Environment(loader=FileSystemLoader('')) tmpl = env.get_template(html_file) return tmpl.render() page_header = render_template('Header.html') page_body = render_template('Body.html') page_footer = render_template('Footer.html) However, this means that each part is created in its own environment - can that be a problem? Are there any other downsides to this approach? I have chosen the 3-part approach over the child-template approach because I think it may be more flexible (and easier to follow), but I might be wrong. Anyone like to convince me that using header, body and footer blocks might be better? Any advice would be appreciated. Alan

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  • Rails validation count limit on has_many :through

    - by Jeremy
    I've got the following models: Team, Member, Assignment, Role The Team model has_many Members. Each Member has_many roles through assignments. Role assignments are Captain and Runner. I have also installed devise and CanCan using the Member model. What I need to do is limit each Team to have a max of 1 captain and 5 runners. I found this example, and it seemed to work after some customization, but on update ('teams/1/members/4/edit'). It doesn't work on create ('teams/1/members/new'). But my other validation (validates :role_ids, :presence = true ) does work on both update and create. Any help would be appreciated. Update: I've found this example that would seem to be similar to my problem but I can't seem to make it work for my app. It seems that the root of the problem lies with how the count (or size) is performed before and during validation. For Example: When updating a record... It checks to see how many runners there are on a team and returns a count. (i.e. 5) Then when I select a role(s) to add to the member it takes the known count from the database (i.e. 5) and adds the proposed changes (i.e. 1), and then runs the validation check. (Team.find(self.team_id).members.runner.count 5) This works fine because it returns a value of 6 and 6 5 so the proposed update fails without saving and an error is given. But when I try to create a new member on the team... It checks to see how many runners there are on a team and returns a count. (i.e. 5) Then when I select a role(s) to add to the member it takes the known count from the database (i.e. 5) and then runs the validation check WITHOUT factoring in the proposed changes. This doesn't work because it returns a value of 5 known runner and 5 = 5 so the proposed update passes and the new member and role is saved to the database with no error. Member Model: class Member < ActiveRecord::Base devise :database_authenticatable, :registerable, :recoverable, :rememberable, :trackable, :validatable attr_accessible :password, :password_confirmation, :remember_me attr_accessible :age, :email, :first_name, :last_name, :sex, :shirt_size, :team_id, :assignments_attributes, :role_ids belongs_to :team has_many :assignments, :dependent => :destroy has_many :roles, through: :assignments accepts_nested_attributes_for :assignments scope :runner, joins(:roles).where('roles.title = ?', "Runner") scope :captain, joins(:roles).where('roles.title = ?', "Captain") validate :validate_runner_count validate :validate_captain_count validates :role_ids, :presence => true def validate_runner_count if Team.find(self.team_id).members.runner.count > 5 errors.add(:role_id, 'Error - Max runner limit reached') end end def validate_captain_count if Team.find(self.team_id).members.captain.count > 1 errors.add(:role_id, 'Error - Max captain limit reached') end end def has_role?(role_sym) roles.any? { |r| r.title.underscore.to_sym == role_sym } end end Member Controller: class MembersController < ApplicationController load_and_authorize_resource :team load_and_authorize_resource :member, :through => :team before_filter :get_team before_filter :initialize_check_boxes, :only => [:create, :update] def get_team @team = Team.find(params[:team_id]) end def index respond_to do |format| format.html # index.html.erb format.json { render json: @members } end end def show respond_to do |format| format.html # show.html.erb format.json { render json: @member } end end def new respond_to do |format| format.html # new.html.erb format.json { render json: @member } end end def edit end def create respond_to do |format| if @member.save format.html { redirect_to [@team, @member], notice: 'Member was successfully created.' } format.json { render json: [@team, @member], status: :created, location: [@team, @member] } else format.html { render action: "new" } format.json { render json: @member.errors, status: :unprocessable_entity } end end end def update respond_to do |format| if @member.update_attributes(params[:member]) format.html { redirect_to [@team, @member], notice: 'Member was successfully updated.' } format.json { head :no_content } else format.html { render action: "edit" } format.json { render json: @member.errors, status: :unprocessable_entity } end end end def destroy @member.destroy respond_to do |format| format.html { redirect_to team_members_url } format.json { head :no_content } end end # Allow empty checkboxes # http://railscasts.com/episodes/17-habtm-checkboxes def initialize_check_boxes params[:member][:role_ids] ||= [] end end _Form Partial <%= form_for [@team, @member], :html => { :class => 'form-horizontal' } do |f| %> #... # testing the count... <ul> <li>Captain - <%= Team.find(@member.team_id).members.captain.size %></li> <li>Runner - <%= Team.find(@member.team_id).members.runner.size %></li> <li>Driver - <%= Team.find(@member.team_id).members.driver.size %></li> </ul> <div class="control-group"> <div class="controls"> <%= f.fields_for :roles do %> <%= hidden_field_tag "member[role_ids][]", nil %> <% Role.all.each do |role| %> <%= check_box_tag "member[role_ids][]", role.id, @member.role_ids.include?(role.id), id: dom_id(role) %> <%= label_tag dom_id(role), role.title %> <% end %> <% end %> </div> </div> #... <% end %>

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  • Google App Engine with local Django 1.1 gets Intermittent Failures

    - by Jon Watte
    I'm using the Windows Launcher development environment for Google App Engine. I have downloaded Django 1.1.2 source, and un-tarrred the "django" subdirectory to live within my application directory (a peer of app.yaml) At the top of each .py source file, I do this: import settings import os os.environ["DJANGO_SETTINGS_MODULE"] = 'settings' In my file settings.py (which lives at the root of the app directory, as well), I do this: DEBUG = True TEMPLATE_DIRS = ('html') INSTALLED_APPS = ('filters') import os os.environ["DJANGO_SETTINGS_MODULE"] = 'settings' from google.appengine.dist import use_library use_library('django', '1.1') from django.template import loader Yes, this looks a bit like overkill, doesn't it? I only use django.template. I don't explicitly use any other part of django. However, intermittently I get one of two errors: 1) Django complains that DJANGO_SETTINGS_MODULE is not defined. 2) Django complains that common.html (a template I'm extending in other templates) doesn't exist. 95% of the time, these errors are not encountered, and they randomly just start happening. Once in that state, the local server seems "wedged" and re-booting it generally fixes it. What's causing this to happen, and what can I do about it? How can I even debug it? Here is the traceback from the error: Traceback (most recent call last): File "C:\code\kwbudget\edit_budget.py", line 34, in get self.response.out.write(t.render(template.Context(values))) File "C:\code\kwbudget\django\template\__init__.py", line 165, in render return self.nodelist.render(context) File "C:\code\kwbudget\django\template\__init__.py", line 784, in render bits.append(self.render_node(node, context)) File "C:\code\kwbudget\django\template\__init__.py", line 797, in render_node return node.render(context) File "C:\code\kwbudget\django\template\loader_tags.py", line 71, in render compiled_parent = self.get_parent(context) File "C:\code\kwbudget\django\template\loader_tags.py", line 66, in get_parent raise TemplateSyntaxError, "Template %r cannot be extended, because it doesn't exist" % parent TemplateSyntaxError: Template u'common.html' cannot be extended, because it doesn't exist And edit_budget.py starts with exactly the lines that I included up top. All templates live in a directory named "html" in my root directory, and "html/common.html" exists. I know the template engine finds them, because I start out with "html/edit_budget.html" which extends common.html. It looks as if the settings module somehow isn't applied (because that's what adds html to the search path for templates).

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  • Opengl: use a texture only to give alpha channel to a colored object

    - by Damian
    I'm new at OpenGL and I can't find out how to do this: I want to render a letter and be able to change it's color, so I have a texture with the letter on a transparent background. I managed to render it using this code: glEnable(GL_BLEND) glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) But that renders the letter in black, as it's on the texture. How can I render it with the color setted with glColor4f?

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  • running requestAnimationFrame from within a new object

    - by JVE999
    I'm having trouble running an animation. This is inside var ob1 = function() {};. When called, it runs for a while and then I get the error Uncaught RangeError: Maximum call stack size exceeded. However, this same structure has no problems running outside of the object. /////////////// Render the scene /////////////// this.render = function (){ renderer.render(scene,camera); if(isControls == true) controls.update(clock.getDelta()); this.animate(); //console.log(true); requestAnimationFrame(this.render()); } /////////////// Update objects /////////////// this.animate = function (){ console.log("!"); }

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  • How to generate real UTF-8 XML with grails without the escape characters?

    - by AngeDeLaMort
    I have been wondering why when I set the encoding to UTF-8 and rendering the XML it replace the extended characters by escape characters (or character reference) like &#x2019; instead of '? I'm using the Render method render(contentType:"text/xml", encoding:"UTF-8") {...} with a proper header render(contentType:"text/xml", encoding:"UTF-8", text:"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n") Any idea if there is a way to write it properly? Thanks.

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  • adding a column dynamically and hiding the first column like jquery slider ..

    - by paul
    I have a html page with 10 columns but I don't have show all in same page instead I have to show only 4 column moreover I have to render those column on a button click call add column. What is the best approach to render 1-4 column first ? Fist column render first and on clicking button say add will render 2nd column , than 3rd and fourth. Now when i will load 5th column ...I will have to hide 1st column so that i will accommodate 4 columns but data inside that column will stay ....my limit is to show 4 column at a time and hiding leftmost .... any helpful javascript or jquery advice will be appreciated ..thanks!

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  • Validate HAML from ActiveRecord: scope/controller/helpers for link_to etc?

    - by Chris Boyle
    I like HAML. So much, in fact, that in my first Rails app, which is the usual blog/CMS thing, I want to render the body of my Page model using HAML. So here is app/views/pages/_body.html.haml: .entry-content= Haml::Engine.new(body, :format => :html5).render ...and it works (yay, recursion). What I'd like to do is validate the HAML in the body when creating or updating a Page. I can almost do that, but I'm stuck on the scope argument to render. I have this in app/models/page.rb: validates_each :body do |record, attr, value| begin Haml::Engine.new(value, :format => :html5).render(record) rescue Exception => e record.errors.add attr, "line #{(e.respond_to? :line) && e.line || 'unknown'}: #{e.message}" end end You can see I'm passing record, which is a Page, but even that doesn't have a controller, and in particular doesn't have any helpers like link_to, so as soon as a Page uses any of that it's going to fail to validate even when it would actually render just fine. So I guess I need a controller as scope for this, but accessing that from here in the model (where the validator is) is a big MVC no-no, and as such I don't think Rails gives me a way to do it. (I mean, I suppose I could stash a controller in some singleton somewhere or something, but... excuse me while I throw up.) What's the least ugly way to properly validate HAML in an ActiveRecord validator?

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  • How can I reduce the number of loops in this VIEW in Rails when using :collection?

    - by Angela
    I am using the :collection to go through all the Contacts that are part of a given Campaign. But within that Campaign I check for three different Models (each with their own partial). Feels like I am going through the list of Contacts 3x. How can I make this alot leaner? <h2>These are past due:</h2> <% @campaigns.each do |campaign| %> <h3>Campaign: <%= link_to campaign.name, campaign %></h3> <strong>Emails in this Campaign:</strong> <% for email in campaign.emails %> <h4><%= link_to email.title, email %> <%= email.days %> days</h4> <% @contacts= campaign.contacts.find(:all, :order => "date_entered ASC" )%> <!--contacts collection--> <!-- render the information for each contact --> <%= render :partial => "contact_email", :collection => @contacts, :locals => {:email => email} %> <% end %> Calls in this Campaign: <% for call in campaign.calls %> <h4><%= link_to call.title, call %> <%= call.days %> days</h4> <% @contacts= campaign.contacts.find(:all, :order => "date_entered ASC" )%> <!--contacts collection--> <!-- render the information for each contact --> <%= render :partial => "contact_call", :collection => @contacts, :locals => {:call => call} %> <% end %> Letters in this Campaign: <% for letter in campaign.letters %> <h4><%= link_to letter.title, letter %> <%= letter.days %> days</h4> <% @contacts= campaign.contacts.find(:all, :order => "date_entered ASC" )%> <!--contacts collection--> <!-- render the information for each contact --> <%= render :partial => "contact_letter", :collection => @contacts, :locals => {:letter => letter} %> <% end %> <% end %>

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  • How to use Spanish characters in Handlebars templates

    - by Jon Rose
    I am wondering what the idiomatic way to render special language characters is using Handlebars.js templates. When I render the normal html I can use something like the Spanish lowercase e, &#233, and it renders as expected. When I pass the same text as a string to my Handlebars template I just see the characters &#233. I have tried creating a Handlebars helper that used jquery to render the text using .html() then returning the .html() of the tmp element and I get the same results.

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  • FOSUserBundle: embedding the login form and choosing its template

    - by tirengarfio
    i want to insert the login form of FOSUserBundle in my template like this: <div id="sidebar"> {% render "FOSUserBundle::Security::login" %} </div> but not to render the template that is been calling in the code of loginAction() originally. I have thought I'd find useful the possibility of passing the template I want to render as a parameter as 'max' in this example: <div id="sidebar"> {% render "AcmeArticleBundle:Article:recentArticles" with {'max': 3} %} </div> Is that possible in symfony2? If not.. should I create another action for my bundle with the same code inside of loginAction? or should I modify the original loginAction code and write control structures? if(currentPage == 'home') renderResponse('template1') else renderResponse('template2')

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  • How refresh a DrawingArea in PyGTK ?

    - by Lialon
    I have an interface created with Glade. It contains a DrawingArea and buttons. I tried to create a Thread to refresh every X time my Canva. After a few seconds, I get error messages like: "X Window Server 0.0", "Fatal Error IO 11" Here is my code : import pygtk pygtk.require("2.0") import gtk import Canvas import threading as T import time import Map gtk.gdk.threads_init() class Interface(object): class ThreadCanvas(T.Thread): """Thread to display the map""" def __init__(self, interface): T.Thread.__init__(self) self.interface = interface self.started = True self.start() def run(self): while self.started: time.sleep(2) self.interface.on_canvas_expose_event() def stop(self): self.started = False def __init__(self): self.interface = gtk.Builder() self.interface.add_from_file("interface.glade") #Map self.map = Map.Map(2,2) #Canva self.canvas = Canvas.MyCanvas(self.interface.get_object("canvas"),self.game) self.interface.connect_signals(self) #Thread Canvas self.render = self.ThreadCanvas(self) def on_btnChange_clicked(self, widget): #Change map self.map.change() def on_interface_destroy(self, widget): self.render.stop() self.render.join() self.render._Thread__stop() gtk.main_quit() def on_canvas_expose_event(self): st = time.time() self.canvas.update(self.map) et = time.time() print "Canvas refresh in : %f times" %(et-st) def main(self): gtk.main() How can i fix these errors ?

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  • OpenGL ES Polygon with Normals rendering (Note the 'ES!')

    - by MarqueIV
    Ok... imagine I have a relatively simple solid that has six distinct normals but actually has close to 48 faces (8 faces per direction) and there are a LOT of shared vertices between faces. What's the most efficient way to render that in OpenGL? I know I can place the vertices in an array, then use an index array to render them, but I have to keep breaking my rendering steps down to change the normals (i.e. set normal 1... render 8 faces... set normal 2... render 8 faces, etc.) Because of that I have to maintain an array of index arrays... one for each normal! Not good! The other way I can do it is to use separate normal and vertex arrays (or even interleave them) but that means I need to have a one-to-one ratio for normals to vertices and that means the normals would be duplicated 8 times more than they need to be! On something with a spherical or even curved surface, every normal most likely is different, but for this, it really seems like a waste of memory. In a perfect world I'd like to have my vertex and normal arrays have different lengths, then when I go to draw my triangles or quads To specify the index to each array for that vertex. Now the OBJ file format lets you specify exactly that... a vertex array and a normal array of different lengths, then when you specify the face you are rendering, you specify a vertex and a normal index (as well as a UV coord if you are using textures too) which seems like the perfect solution! 48 vertices but only 8 normals, then pairs of indexes defining the shapes' faces. But I'm not sure how to render that in OpenGL ES (again, note the 'ES'.) Currently I have to 'denormalize' (sorry for the SQL pun there) the normals back to a 1-to-1 with the vertex array, then render. Just wastes memory to me. Anyone help? I hope I'm missing something very simple here. Mark

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  • Strange errors in Visual C++ :: 'malloc' : function does not take 1 arguments

    - by pecker
    Error 38 error C2660: 'malloc' : function does not take 1 arguments C:\VolumeRenderer\render.cpp 296 1 VolumeRenderer Error 39 error C2660: 'malloc' : function does not take 1 arguments C:\VolumeRenderer\render.cpp 412 1 VolumeRenderer Error 40 error C2660: 'malloc' : function does not take 1 arguments C:\VolumeRenderer\render.cpp 414 1 VolumeRenderer Error 41 error C2660: 'read_den' : function does not take 4 arguments C:\VolumeRenderer\render.cpp 506 1 VolumeRenderer My all malloc sections are like this: /* allocate space for the raw data */ density_size = BRAIN_XLEN * BRAIN_YLEN * BRAIN_ZLEN; density = (unsigned char*)malloc(density_size); if (density == NULL) { fprintf(stderr, "out of memory\n"); exit(1); } regarding read_den (last error) unsigned char *read_den(char *filename,int *xptr,int *yptr,int *zptr)// function prototype src_volume = read_den(src_file, &src_xlen, &src_ylen, &src_zlen);// fucntion call Is it my code or the errors that are absurd. How to rectify them?

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  • What is wrong with my @synchronized block?

    - by hyn
    I have 2 threads in my application, a game update thread and render/IO/main thread. My update thread updates the game state, and the render thread renders the scene based on the updated values of the game state models and a few other variables stored inside an object (gameEngine). The render thread gets executed while the game thread is still updating, which is a problem, so it appeared to me the solution is to use @synchronized like this: @synchronized(gameEngine) { [gameEngine update]; nextUpdate = now + GAME_UPDATE_INTERVAL; gameEngine.lastGameUpdateInterval = now - lastUpdate; gameEngine.lastGameUpdateTime = now; lastUpdate = now; } But the render thread still accesses the gameEngine object between -update and the last 3 lines of the block. Why is this?

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  • My partial is not where rails expects it to be (nested partials)

    - by new2ruby
    I have a model Submissions which has many Performers. I have a partial for showing an individual submissions (app/views/submissions/_submission.html.erb): <div> Show stuff relating to @submission ... <%= render @performers %> </div> and a partial for showing performers (app/views/performers/_performer.html.erb): <%= div_for performer do %> <%= performer.name %> <% end %> This works fine from (app/views/submissions/show.html.erb): <%= render @submission %> But I want to use this from a different namespace too (app/views/curator/submissions/show.html.erb). But I get this error: Missing partial curator/submissions/submission with {:locale=>[:en], :formats=>[:html], :handlers=>[:erb, :builder, :coffee]}. Searched in: * "/Users/ircmullaney/RubyCode/cif/app/views" * "/Users/ircmullaney/.rvm/gems/ruby-1.9.3-p194@rails3tutorial2ndEd/gems/devise-2.1.2/app/views" I can fix this by changing the render to this: <%= render 'submissions/submission' %> But, then the nested partial fails: Missing partial curator/performers/performer with {:locale=>[:en], :formats=>[:html], :handlers=>[:erb, :builder, :coffee]}. Searched in: * "/Users/ircmullaney/RubyCode/cif/app/views" * "/Users/ircmullaney/.rvm/gems/ruby-1.9.3-p194@rails3tutorial2ndEd/gems/devise-2.1.2/app/views" This doesn't work: <%= render 'performers/performer' %> because of the div_for: undefined method `model_name' for NilClass:Class Any ideas how I should do this?

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  • Having different database sorting order (default_scope) for two different views

    - by Juniper747
    In my model (pins.rb), I have two sorting orders: default_scope order: 'pins.featured DESC' #for adding featured posts to the top of a list default_scope order: 'pins.created_at DESC' #for adding the remaining posts beneath the featured posts This sorting order (above) is how I want my 'pins view' (index.html.erb) to look. Which is just a list of ALL user posts. In my 'users view' (show.html.erb) I am using the same model (pins.rb) to list only current_user pins. HOWEVER, I want to sorting order to ignore the "featured" default scope and only use the second scope: default_scope order: 'pins.created_at DESC' How can I accomplish this? I tried doing something like this: default_scope order: 'pins.featured DESC', only: :index default_scope order: 'pins.created_at DESC' But that didn't fly... UPDATE I updated my model to define a scope: scope :featy, order: 'pins.featured DESC' default_scope order: 'pins.created_at DESC' And updated my pins view to: <%= render @pins.featy %> However, now when I open my pins view, I get the error: undefined method `featy' for #<Array:0x00000100ddbc78> UPDATE 2 User.rb class User < ActiveRecord::Base attr_accessible :name, :email, :username, :password, :password_confirmation, :avatar, :password_reset_token, :password_reset_sent_at has_secure_password has_many :pins, dependent: :destroy #destroys user posts when user is destroyed # has_many :featured_pins, order: 'featured DESC', class_name: "Pin", source: :pin has_attached_file :avatar, :styles => { :medium => "300x300#", :thumb => "120x120#" } before_save { |user| user.email = user.email.downcase } before_save { |user| user.username = user.username.downcase } before_save :create_remember_token before_save :capitalize_name validates :name, presence: true, length: { maximum: 50 } VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i VALID_USERNAME_REGEX = /^[A-Za-z0-9]+(?:[_][A-Za-z0-9]+)*$/ validates :email, presence: true, format: { with: VALID_EMAIL_REGEX }, uniqueness: { case_sensitive: false } validates :username, presence: true, format: { with: VALID_USERNAME_REGEX }, uniqueness: { case_sensitive: false } validates :password, length: { minimum: 6 }, on: :create #on create, because was causing erros on pw_reset Pin.rb class Pin < ActiveRecord::Base attr_accessible :content, :title, :privacy, :date, :dark, :bright, :fragmented, :hashtag, :emotion, :user_id, :imagesource, :imageowner, :featured belongs_to :user before_save :capitalize_title before_validation :generate_slug validates :content, presence: true, length: { maximum: 8000 } validates :title, presence: true, length: { maximum: 24 } validates :imagesource, presence: { message: "Please search and choose an image" }, length: { maximum: 255 } validates_inclusion_of :privacy, :in => [true, false] validates :slug, uniqueness: true, presence: true, exclusion: {in: %w[signup signin signout home info privacy]} # for sorting featured and newest posts first default_scope order: 'pins.created_at DESC' scope :featured_order, order: 'pins.featured DESC' def to_param slug # or "#{id}-#{name}".parameterize end def generate_slug # makes the url slug address bar freindly self.slug ||= loop do random_token = Digest::MD5.hexdigest(Time.zone.now.to_s + title)[0..9]+"-"+"#{title}".parameterize break random_token unless Pin.where(slug: random_token).exists? end end protected def capitalize_title self.title = title.split.map(&:capitalize).join(' ') end end users_controller.rb class UsersController < ApplicationController before_filter :signed_in_user, only: [:edit, :update, :show] before_filter :correct_user, only: [:edit, :update, :show] before_filter :admin_user, only: :destroy def index if !current_user.admin? redirect_to root_path end end def menu @user = current_user end def show @user = User.find(params[:id]) @pins = @user.pins current_user.touch(:last_log_in) #sets the last log in time if [email protected]? render 'pages/info/' end end def new @user = User.new end pins_controller.rb class PinsController < ApplicationController before_filter :signed_in_user, except: [:show] # GET /pins, GET /pins.json def index #Live Feed @pins = Pin.all @featured_pins = Pin.featured_order respond_to do |format| format.html # index.html.erb format.json { render json: @pins } end end # GET /pins, GET /pins.json def show #single Pin View @pin = Pin.find_by_slug!(params[:id]) require 'uri' #this gets the photo's id from the stored uri @image_id = URI(@pin.imagesource).path.split('/').second if @pin.privacy == true #check for private pins if signed_in? if @pin.user_id == current_user.id respond_to do |format| format.html # show.html.erb format.json { render json: @pin } end else redirect_to home_path, notice: "Prohibited 1" end else redirect_to home_path, notice: "Prohibited 2" end else respond_to do |format| format.html # show.html.erb format.json { render json: @pin } end end end # GET /pins, GET /pins.json def new @pin = current_user.pins.new respond_to do |format| format.html # new.html.erb format.json { render json: @pin } end end # GET /pins/1/edit def edit @pin = current_user.pins.find_by_slug!(params[:id]) end Finally, on my index.html.erb I have: <%= render @featured_pins %>

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  • Returning a 1x1 .gif as a response in Rails

    - by Avishai
    Hi, I'm building a Rails app that does conversion tracking on outside sites. I'd like to allow users to paste an image tag in their conversion pages (like AdWords), and whenever that image is requested, a conversion registers in my app. respond_to do |format| if @conversion.save flash[:notice] = 'Conversion was successfully created.' format.html { redirect_to(@conversion) } format.xml { render :xml => @conversion, :status => :created, :location => @conversion } format.js { render :json => @conversion, :status => :created } format.gif { head :status => :ok } else format.html { render :action => "new" } format.xml { render :xml => @conversion.errors, :status => :unprocessable_entity } end end This way, the browser gets a non-existent .gif image. Is there a better way to do this?

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  • What are the Rails best practices for javascript templates in restful/resourceful controllers?

    - by numbers1311407
    First, 2 common (basic) approaches: # returning from some FoosController method respond_to do |format| # 1. render the javascript directly format.js { render :json => @foo.to_json } # 2. render the default template, say update.js.erb format.js { render } end # in update.js.erb $('#foo').html("<%= escape_javascript(render(@foo)) %>") These are obviously simple cases but I wanted to illustrate what I'm talking about. I believe that these are also the cases expected by the default responder in rails 3 (either the action-named default template or calling to_#{format} on the resource.) The Issues With 1, you have total flexibility on the view side with no worries about the template, but you have to manipulate the DOM directly via javascript. You lose access to helpers, partials, etc. With 2, you have partials and helpers at your disposal, but you're tied to the one template (by default at least). All your views that make JS calls to FoosController use the same template, which isn't exactly flexible. Three Other Approaches (none really satisfactory) 1.) Escape partials/helpers I need into javascript beforehand, then inserting them into the page after, using string replacement to tailor them to the results returned (subbing in name, id, etc). 2.) Put view logic in the templates. For example, looking for a particular DOM element and doing one thing if it exists, another if it does not. 3.) Put logic in the controller to render different templates. For example, in a polymorphic belongs to where update might be called for either comments/foo or posts/foo, rendering commnts/foos/update.js.erb versus posts/foos/update.js.erb. I've used all of these (and probably others I'm not thinking of). Often in the same app, which leads to confusing code. Are there best practices for this sort of thing? It seems like a common enough use-case that you'd want to call controllers via Ajax actions from different views and expect different things to happen (without having to do tedious things like escaping and string-replacing partials and helpers client side). Any thoughts?

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  • Libgdx - 2D Mesh rendering overlap glitch

    - by user46858
    I am trying to render a 2D circle segment mesh (quarter circle)using Libgdx/Opengl ES 2.0 but I seem to be getting an overlapping issue as seen in the picture attached. I cant seem to find the cause of the problem but the overlapping disappears/reappears if I drag and resize the window to random sizes. The problem occurs on both pc and android. The strange thing is the first two segments atleast dont seem to be causing any overlapping only the third and/or forth segment.......even though they are all rendered using the same mesh object..... I have spent ages trying to find the cause of the problem before posting here for help so ANY help/advice in finding the cause of this problem would be really appreciated. public class MyGdxGame extends Game { private SpriteBatch batch; private Texture texture; private OrthographicCamera myCamera; private float w; private float h; private ShaderProgram circleSegShader; private Mesh circleScaleSegMesh; private Stage stage; private float TotalSegments; Vector3 virtualres; @Override public void create() { w = Gdx.graphics.getWidth(); h = Gdx.graphics.getHeight(); batch = new SpriteBatch(); ViewPortsize = new Vector2(); TotalSegments = 4.0f; virtualres = new Vector3(1280.0f, 720.0f, 0.0f); myCamera = new OrthographicCamera(); myCamera.setToOrtho(false, w, h); texture = new Texture(Gdx.files.internal("data/libgdx.png")); texture.setFilter(TextureFilter.Linear, TextureFilter.Linear); circleScaleSegMesh = createCircleMesh_V3(0.0f,0.0f,200.0f, 30.0f,3, (360.0f /TotalSegments) ); circleSegShader = loadShaderFromFile(new String("circleseg.vert"), new String("circleseg.frag")); shaderProgram.pedantic = false; stage = new Stage(); stage.setViewport(new ExtendViewport(w, h)); Gdx.input.setInputProcessor(stage); } @Override public void render() { .... //render renderInit(); renderCircleScaledSegment(); } @Override public void resize(int width, int height) { stage.getViewport().update(width, height, true); myCamera.position.set( virtualres.x/2.0f, virtualres.y/2.0f, 0.0f); myCamera.update(); } public void renderInit(){ Gdx.gl20.glClearColor(1.0f, 1.0f, 1.0f, 0.0f); Gdx.gl20.glClear(GL20.GL_COLOR_BUFFER_BIT | GL20.GL_DEPTH_BUFFER_BIT); batch.setShader(null); batch.setProjectionMatrix(myCamera.combined); } public void renderCircleScaledSegment(){ Gdx.gl20.glEnable(GL20.GL_DEPTH_TEST); Gdx.gl20.glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA); Gdx.gl20.glEnable(GL20.GL_BLEND); batch.begin(); circleSegShader.begin(); Matrix4 modelMatrix = new Matrix4(); Matrix4 cameraMatrix = new Matrix4(); Matrix4 cameraMatrix2 = new Matrix4(); Matrix4 cameraMatrix3 = new Matrix4(); Matrix4 cameraMatrix4 = new Matrix4(); cameraMatrix = myCamera.combined.cpy(); modelMatrix.idt().rotate(new Vector3(0.0f,0.0f,1.0f), 0.0f - ((360.0f /TotalSegments)/ 2.0f)).trn(virtualres.x/2.0f,virtualres.y/2.0f, 0.0f); cameraMatrix.mul(modelMatrix); cameraMatrix2 = myCamera.combined.cpy(); modelMatrix.idt().rotate(new Vector3(0.0f,0.0f,1.0f), 0.0f - ((360.0f /TotalSegments)/ 2.0f) +(360.0f /TotalSegments) ).trn(virtualres.x/2.0f,virtualres.y/2.0f, 0.0f); cameraMatrix2.mul(modelMatrix); cameraMatrix3 = myCamera.combined.cpy(); modelMatrix.idt().rotate(new Vector3(0.0f,0.0f,1.0f), 0.0f - ((360.0f /TotalSegments)/ 2.0f) +(2*(360.0f /TotalSegments))).trn(virtualres.x/2.0f,virtualres.y/2.0f, 0.0f); cameraMatrix3.mul(modelMatrix); cameraMatrix4 = myCamera.combined.cpy(); modelMatrix.idt().rotate(new Vector3(0.0f,0.0f,1.0f),0.0f - ((360.0f /TotalSegments)/ 2.0f) +(3*(360.0f /TotalSegments)) ).trn(virtualres.x/2.0f,virtualres.y/2.0f, 0.0f); cameraMatrix4.mul(modelMatrix); Vector3 box2dpos = new Vector3(0.0f, 0.0f, 0.0f); circleSegShader.setUniformMatrix("u_projTrans", cameraMatrix); circleSegShader.setUniformf("u_box2dpos", box2dpos); circleSegShader.setUniformi("u_texture", 0); texture.bind(); circleScaleSegMesh.render(circleSegShader, GL20.GL_TRIANGLES); circleSegShader.setUniformMatrix("u_projTrans", cameraMatrix2); circleSegShader.setUniformf("u_box2dpos", box2dpos); circleSegShader.setUniformi("u_texture", 0); texture.bind(); circleScaleSegMesh.render(circleSegShader, GL20.GL_TRIANGLES); circleSegShader.setUniformMatrix("u_projTrans", cameraMatrix3); circleSegShader.setUniformf("u_box2dpos", box2dpos); circleSegShader.setUniformi("u_texture", 0); texture.bind(); circleScaleSegMesh.render(circleSegShader, GL20.GL_TRIANGLES); circleSegShader.setUniformMatrix("u_projTrans", cameraMatrix4); circleSegShader.setUniformf("u_box2dpos", box2dpos); circleSegShader.setUniformi("u_texture", 0); texture.bind(); circleScaleSegMesh.render(circleSegShader, GL20.GL_TRIANGLES); circleSegShader.end(); batch.flush(); batch.end(); Gdx.gl20.glDisable(GL20.GL_DEPTH_TEST); Gdx.gl20.glDisable(GL20.GL_BLEND); } public Mesh createCircleMesh_V3(float cx, float cy, float r_out, float r_in, int num_segments, float segmentSizeDegrees){ float theta = (float) (2.0f * MathUtils.PI / (num_segments * (360.0f / segmentSizeDegrees))); float c = MathUtils.cos(theta);//precalculate the sine and cosine float s = MathUtils.sin(theta); float t,t2; float x = r_out;//we start at angle = 0 float y = 0; float x2 = r_in;//we start at angle = 0 float y2 = 0; float[] meshCoords = new float[num_segments *2 *3 *7]; int arrayIndex = 0; //array for triangles without indices for(int ii = 0; ii < num_segments; ii++) { meshCoords[arrayIndex] = x2+cx; meshCoords[arrayIndex +1] = y2+cy; meshCoords[arrayIndex +2] = 0.0f; meshCoords[arrayIndex +3] = 63.0f/255.0f; meshCoords[arrayIndex +4] = 139.0f/255.0f; meshCoords[arrayIndex +5] = 217.0f/255.0f; meshCoords[arrayIndex +6] = 0.7f; arrayIndex = arrayIndex + 7; meshCoords[arrayIndex] = x+cx; meshCoords[arrayIndex +1] = y+cy; meshCoords[arrayIndex +2] = 0.0f; meshCoords[arrayIndex +3] = 63.0f/255.0f; meshCoords[arrayIndex +4] = 139.0f/255.0f; meshCoords[arrayIndex +5] = 217.0f/255.0f; meshCoords[arrayIndex +6] = 0.7f; arrayIndex = arrayIndex + 7; t = x; x = c * x - s * y; y = s * t + c * y; meshCoords[arrayIndex] = x+cx; meshCoords[arrayIndex +1] = y+cy; meshCoords[arrayIndex +2] = 0.0f; meshCoords[arrayIndex +3] = 63.0f/255.0f; meshCoords[arrayIndex +4] = 139.0f/255.0f; meshCoords[arrayIndex +5] = 217.0f/255.0f; meshCoords[arrayIndex +6] = 0.7f; arrayIndex = arrayIndex + 7; meshCoords[arrayIndex] = x2+cx; meshCoords[arrayIndex +1] = y2+cy; meshCoords[arrayIndex +2] = 0.0f; meshCoords[arrayIndex +3] = 63.0f/255.0f; meshCoords[arrayIndex +4] = 139.0f/255.0f; meshCoords[arrayIndex +5] = 217.0f/255.0f; meshCoords[arrayIndex +6] = 0.7f; arrayIndex = arrayIndex + 7; meshCoords[arrayIndex] = x+cx; meshCoords[arrayIndex +1] = y+cy; meshCoords[arrayIndex +2] = 0.0f; meshCoords[arrayIndex +3] = 63.0f/255.0f; meshCoords[arrayIndex +4] = 139.0f/255.0f; meshCoords[arrayIndex +5] = 217.0f/255.0f; meshCoords[arrayIndex +6] = 0.7f; arrayIndex = arrayIndex + 7; t2 = x2; x2 = c * x2 - s * y2; y2 = s * t2 + c * y2; meshCoords[arrayIndex] = x2+cx; meshCoords[arrayIndex +1] = y2+cy; meshCoords[arrayIndex +2] = 0.0f; meshCoords[arrayIndex +3] = 63.0f/255.0f; meshCoords[arrayIndex +4] = 139.0f/255.0f; meshCoords[arrayIndex +5] = 217.0f/255.0f; meshCoords[arrayIndex +6] = 0.7f; arrayIndex = arrayIndex + 7; } Mesh myMesh = new Mesh(VertexDataType.VertexArray, false, meshCoords.length, 0, new VertexAttribute(VertexAttributes.Usage.Position, 3, "a_position"), new VertexAttribute(VertexAttributes.Usage.Color, 4, "a_color")); myMesh.setVertices(meshCoords); return myMesh; } }

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  • Day 6 - Game Menuing Woes and Future Screen Sneak Peeks

    - by dapostolov
    So, after my last post on Day 5 I dabbled with my game class design. I took the approach where each game objects is tightly coupled with a graphic. The good news is I got the menu working but not without some hard knocks and game growing pains. I'll explain later, but for now...here is a class diagram of my first stab at my class structure and some code...   Ok, there are few mistakes, however, I'm going to leave it as is for now... As you can see I created an inital abstract base class called GameSprite. This class when inherited will provide a simple virtual default draw method:        public virtual void DrawSprite(SpriteBatch spriteBatch)         {             spriteBatch.Draw(Sprite, Position, Color.White);         } The benefits of coding it this way allows me to inherit the class and utilise the method in the screen draw method...So regardless of what the graphic object type is it will now have the ability to render a static image on the screen. Example: public class MyStaticTreasureChest : GameSprite {} If you remember the window draw method from Day 3's post, we could use the above code as follows...         protected override void Draw(GameTime gameTime)         {             GraphicsDevice.Clear(Color.CornflowerBlue);             spriteBatch.Begin(SpriteBlendMode.AlphaBlend);             foreach(var gameSprite in ListOfGameObjects)            {                 gameSprite.DrawSprite(spriteBatch);            }             spriteBatch.End();             base.Draw(gameTime);         } I have to admit the GameSprite object is pretty plain as with its DrawSprite method... But ... we now have the ability to render 3 static menu items on the screen ... BORING! I want those menu items to do something exciting, which of course involves animation... So, let's have a peek at AnimatedGameSprite in the above game diagram. The idea with the AnimatedGameSprite is that it has an image to animate...such as ... characters, fireballs, and... menus! So after inheriting from GameSprite class, I added a few more options such as UpdateSprite...         public virtual void UpdateSprite(float elapsed)         {             _totalElapsed += elapsed;             if (_totalElapsed > _timePerFrame)             {                 _frame++;                 _frame = _frame % _framecount;                 _totalElapsed -= _timePerFrame;             }         }  And an overidden DrawSprite...         public override void DrawSprite(SpriteBatch spriteBatch)         {             int FrameWidth = Sprite.Width / _framecount;             Rectangle sourcerect = new Rectangle(FrameWidth * _frame, 0, FrameWidth, Sprite.Height);             spriteBatch.Draw(Sprite, Position, sourcerect, Color.White, _rotation, _origin, _scale, SpriteEffects.None, _depth);         } With these two methods...I can animate and image, all I had to do was add a few more lines to the screens Update Method (From Day 3), like such:             float elapsed = (float) gameTime.ElapsedGameTime.TotalSeconds;             foreach (var item in ListOfAnimatedGameObjects)             {                 item.UpdateSprite(elapsed);             } And voila! My images begin to animate in one spot, on the screen... Hmm, but how do I interact with the menu items using a mouse...well the mouse cursor was easy enough... this.IsMouseVisible = true; But, to have it "interact" with an image was a bit more tricky...I had to perform collision detection!             mouseStateCurrent = Mouse.GetState();             var uiEnabledSprites = (from s in menuItems                                    where s.IsEnabled                                    select s).ToList();             foreach (var item in uiEnabledSprites)             {                 var r = new Rectangle((int)item.Position.X, (int)item.Position.Y, item.Sprite.Width, item.Sprite.Height);                 item.MenuState = MenuState.Normal;                 if (r.Intersects(new Rectangle(mouseStateCurrent.X, mouseStateCurrent.Y, 0, 0)))                 {                     item.MenuState = MenuState.Hover;                     if (mouseStatePrevious.LeftButton == ButtonState.Pressed                         && mouseStateCurrent.LeftButton == ButtonState.Released)                     {                         item.MenuState = MenuState.Pressed;                     }                 }             }             mouseStatePrevious = mouseStateCurrent; So, basically, what it is doing above is iterating through all my interactive objects and detecting a rectangle collision and the object , plays the state animation (or static image).  Lessons Learned, Time Burned... So, I think I did well to start, but after I hammered out my prototype...well...things got sloppy and I began to realise some design flaws... At the time: I couldn't seem to figure out how to open another window, such as the character creation screen Input was not event based and it was bugging me My menu design relied heavily on mouse input and I couldn't use keyboard. Mouse input, is tightly bound with graphic rendering / positioning, so its logic will have to be in each scene. Menu animations would stop mid frame, then continue when the action occured again. This is bad, because...what if I had a sword sliding onthe screen? Then it would slide a quarter of the way, then stop due to another action, then render again mid-slide... it just looked sloppy. Menu, Solved!? To solve the above problems I did a little research and I found some great code in the XNA forums. The one worth mentioning was the GameStateManagementSample. With this sample, you can create a basic "text based" menu system which allows you to swap screens, popup screens, play the game, and quit....basic game state management... In my next post I'm going to dwelve a bit more into this code and adapt it with my code from this prototype. Text based menus just won't cut it for me, for now...however, I'm still going to stick with my animated menu item idea. A sneak peek using the Game State Management Sample...with no changes made... Cool Things to Mention: At work ... I tend to break out in random conversations every-so-often and I get talking about some of my challenges with this game (or some stupid observation about something... stupid) During one conversation I was discussing how I should animate my images; I explained that I knew I had to use the Update method provided, but I didn't know how (at the time) to render an image at an appropriate "pace" and how many frames to use, etc.. I also got thinking that if a machine rendered my images faster / slower, that was surely going to f-up my animations. To which a friend, Sheldon,  answered, surely the Draw method is like a camera taking a snapshot of a scene in time. Then it clicked...I understood the big picture of the game engine... After some research I discovered that the Draw method attempts to keep a framerate of 60 fps. From what I understand, the game engine will even leave out a few calls to the draw method if it begins to slow down. This is why we want to put our sprite updates in the update method. Then using a game timer (provided by the engine), we want to render the scene based on real time passed, not framerate. So even the engine renders at 20 fps, the animations will still animate at the same real time speed! Which brings up another point. Why 60 fps? I'm speculating that Microsoft capped it because LCD's dont' refresh faster than 60 fps? On another note, If the game engine knows its falling behind in rendering...then surely we can harness this to speed up our games. Maybe I can find some flag which tell me if the game is lagging, and what the current framerate is, etc...(instead of coding it like I did last time) Sheldon, suggested maybe I can render like WoW does, in prioritised layers...I think he's onto something, however I don't think I'll have that many graphics to worry about such a problem of graphic latency. We'll see. People to Mention: Well,as you are aware I hadn't posted in a couple days and I was surprised to see a few emails and messenger queries about my game progress (and some concern as to why I stopped). I want to thank everyone for their kind words of support and put everyone at ease by stating that I do intend on completing this project. Granted I only have a few hours each night, but, I'll do it. Thank you to Garth for mailing in my next screen! That was a nice surprise! The Sneek Peek you've been waiting for... Garth has also volunteered to render me some wizard images. He was a bit shocked when I asked for them in 2D animated strips. He said I was going backward (and that I have really bad Game Development Lingo). But, I advised Garth that I will use 3D images later...for now...2D images. Garth also had some great game design ideas to add on. I advised him that I will save his ideas and include them in the future design document (for the 3d version?). Lastly, my best friend Alek, is going to join me in developing this game. This was a project we started eons ago but never completed because of our careers. Now, priorities change and we have some spare time on our hands. Let's see what trouble Alek and I can get into! Tonight I'll be uploading my prototypes and base game to a source control for both of us to work off of. D.

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  • A free standing ASP.NET Pager Web Control

    - by Rick Strahl
    Paging in ASP.NET has been relatively easy with stock controls supporting basic paging functionality. However, recently I built an MVC application and one of the things I ran into was that I HAD TO build manual paging support into a few of my pages. Dealing with list controls and rendering markup is easy enough, but doing paging is a little more involved. I ended up with a small but flexible component that can be dropped anywhere. As it turns out the task of creating a semi-generic Pager control for MVC was fairly easily. Now I’m back to working in Web Forms and thought to myself that the way I created the pager in MVC actually would also work in ASP.NET – in fact quite a bit easier since the whole thing can be conveniently wrapped up into an easily reusable control. A standalone pager would provider easier reuse in various pages and a more consistent pager display regardless of what kind of 'control’ the pager is associated with. Why a Pager Control? At first blush it might sound silly to create a new pager control – after all Web Forms has pretty decent paging support, doesn’t it? Well, sort of. Yes the GridView control has automatic paging built in and the ListView control has the related DataPager control. The built in ASP.NET paging has several issues though: Postback and JavaScript requirements If you look at paging links in ASP.NET they are always postback links with javascript:__doPostback() calls that go back to the server. While that works fine and actually has some benefit like the fact that paging saves changes to the page and post them back, it’s not very SEO friendly. Basically if you use javascript based navigation nosearch engine will follow the paging links which effectively cuts off list content on the first page. The DataPager control does support GET based links via the QueryStringParameter property, but the control is effectively tied to the ListView control (which is the only control that implements IPageableItemContainer). DataSource Controls required for Efficient Data Paging Retrieval The only way you can get paging to work efficiently where only the few records you display on the page are queried for and retrieved from the database you have to use a DataSource control - only the Linq and Entity DataSource controls  support this natively. While you can retrieve this data yourself manually, there’s no way to just assign the page number and render the pager based on this custom subset. Other than that default paging requires a full resultset for ASP.NET to filter the data and display only a subset which can be very resource intensive and wasteful if you’re dealing with largish resultsets (although I’m a firm believer in returning actually usable sets :-}). If you use your own business layer that doesn’t fit an ObjectDataSource you’re SOL. That’s a real shame too because with LINQ based querying it’s real easy to retrieve a subset of data that is just the data you want to display but the native Pager functionality doesn’t support just setting properties to display just the subset AFAIK. DataPager is not Free Standing The DataPager control is the closest thing to a decent Pager implementation that ASP.NET has, but alas it’s not a free standing component – it works off a related control and the only one that it effectively supports from the stock ASP.NET controls is the ListView control. This means you can’t use the same data pager formatting for a grid and a list view or vice versa and you’re always tied to the control. Paging Events In order to handle paging you have to deal with paging events. The events fire at specific time instances in the page pipeline and because of this you often have to handle data binding in a way to work around the paging events or else end up double binding your data sources based on paging. Yuk. Styling The GridView pager is a royal pain to beat into submission for styled rendering. The DataPager control has many more options and template layout and it renders somewhat cleaner, but it too is not exactly easy to get a decent display for. Not a Generic Solution The problem with the ASP.NET controls too is that it’s not generic. GridView, DataGrid use their own internal paging, ListView can use a DataPager and if you want to manually create data layout – well you’re on your own. IOW, depending on what you use you likely have very different looking Paging experiences. So, I figured I’ve struggled with this once too many and finally sat down and built a Pager control. The Pager Control My goal was to create a totally free standing control that has no dependencies on other controls and certainly no requirements for using DataSource controls. The idea is that you should be able to use this pager control without any sort of data requirements at all – you should just be able to set properties and be able to display a pager. The Pager control I ended up with has the following features: Completely free standing Pager control – no control or data dependencies Complete manual control – Pager can render without any data dependency Easy to use: Only need to set PageSize, ActivePage and TotalItems Supports optional filtering of IQueryable for efficient queries and Pager rendering Supports optional full set filtering of IEnumerable<T> and DataTable Page links are plain HTTP GET href Links Control automatically picks up Page links on the URL and assigns them (automatic page detection no page index changing events to hookup) Full CSS Styling support On the downside there’s no templating support for the control so the layout of the pager is relatively fixed. All elements however are stylable and there are options to control the text, and layout options such as whether to display first and last pages and the previous/next buttons and so on. To give you an idea what the pager looks like, here are two differently styled examples (all via CSS):   The markup for these two pagers looks like this: <ww:Pager runat="server" id="ItemPager" PageSize="5" PageLinkCssClass="gridpagerbutton" SelectedPageCssClass="gridpagerbutton-selected" PagesTextCssClass="gridpagertext" CssClass="gridpager" RenderContainerDiv="true" ContainerDivCssClass="gridpagercontainer" MaxPagesToDisplay="6" PagesText="Item Pages:" NextText="next" PreviousText="previous" /> <ww:Pager runat="server" id="ItemPager2" PageSize="5" RenderContainerDiv="true" MaxPagesToDisplay="6" /> The latter example uses default style settings so it there’s not much to set. The first example on the other hand explicitly assigns custom styles and overrides a few of the formatting options. Styling The styling is based on a number of CSS classes of which the the main pager, pagerbutton and pagerbutton-selected classes are the important ones. Other styles like pagerbutton-next/prev/first/last are based on the pagerbutton style. The default styling shown for the red outlined pager looks like this: .pagercontainer { margin: 20px 0; background: whitesmoke; padding: 5px; } .pager { float: right; font-size: 10pt; text-align: left; } .pagerbutton,.pagerbutton-selected,.pagertext { display: block; float: left; text-align: center; border: solid 2px maroon; min-width: 18px; margin-left: 3px; text-decoration: none; padding: 4px; } .pagerbutton-selected { font-size: 130%; font-weight: bold; color: maroon; border-width: 0px; background: khaki; } .pagerbutton-first { margin-right: 12px; } .pagerbutton-last,.pagerbutton-prev { margin-left: 12px; } .pagertext { border: none; margin-left: 30px; font-weight: bold; } .pagerbutton a { text-decoration: none; } .pagerbutton:hover { background-color: maroon; color: cornsilk; } .pagerbutton-prev { background-image: url(images/prev.png); background-position: 2px center; background-repeat: no-repeat; width: 35px; padding-left: 20px; } .pagerbutton-next { background-image: url(images/next.png); background-position: 40px center; background-repeat: no-repeat; width: 35px; padding-right: 20px; margin-right: 0px; } Yup that’s a lot of styling settings although not all of them are required. The key ones are pagerbutton, pager and pager selection. The others (which are implicitly created by the control based on the pagerbutton style) are for custom markup of the ‘special’ buttons. In my apps I tend to have two kinds of pages: Those that are associated with typical ‘grid’ displays that display purely tabular data and those that have a more looser list like layout. The two pagers shown above represent these two views and the pager and gridpager styles in my standard style sheet reflect these two styles. Configuring the Pager with Code Finally lets look at what it takes to hook up the pager. As mentioned in the highlights the Pager control is completely independent of other controls so if you just want to display a pager on its own it’s as simple as dropping the control and assigning the PageSize, ActivePage and either TotalPages or TotalItems. So for this markup: <ww:Pager runat="server" id="ItemPagerManual" PageSize="5" MaxPagesToDisplay="6" /> I can use code as simple as: ItemPagerManual.PageSize = 3; ItemPagerManual.ActivePage = 4;ItemPagerManual.TotalItems = 20; Note that ActivePage is not required - it will automatically use any Page=x query string value and assign it, although you can override it as I did above. TotalItems can be any value that you retrieve from a result set or manually assign as I did above. A more realistic scenario based on a LINQ to SQL IQueryable result is even easier. In this example, I have a UserControl that contains a ListView control that renders IQueryable data. I use a User Control here because there are different views the user can choose from with each view being a different user control. This incidentally also highlights one of the nice features of the pager: Because the pager is independent of the control I can put the pager on the host page instead of into each of the user controls. IOW, there’s only one Pager control, but there are potentially many user controls/listviews that hold the actual display data. The following code demonstrates how to use the Pager with an IQueryable that loads only the records it displays: protected voidPage_Load(objectsender, EventArgs e) {     Category = Request.Params["Category"] ?? string.Empty;     IQueryable<wws_Item> ItemList = ItemRepository.GetItemsByCategory(Category);     // Update the page and filter the list down     ItemList = ItemPager.FilterIQueryable<wws_Item>(ItemList); // Render user control with a list view Control ulItemList = LoadControl("~/usercontrols/" + App.Configuration.ItemListType + ".ascx"); ((IInventoryItemListControl)ulItemList).InventoryItemList = ItemList; phItemList.Controls.Add(ulItemList); // placeholder } The code uses a business object to retrieve Items by category as an IQueryable which means that the result is only an expression tree that hasn’t execute SQL yet and can be further filtered. I then pass this IQueryable to the FilterIQueryable() helper method of the control which does two main things: Filters the IQueryable to retrieve only the data displayed on the active page Sets the Totaltems property and calculates TotalPages on the Pager and that’s it! When the Pager renders it uses those values, plus the PageSize and ActivePage properties to render the Pager. In addition to IQueryable there are also filter methods for IEnumerable<T> and DataTable, but these versions just filter the data by removing rows/items from the entire already retrieved data. Output Generated and Paging Links The output generated creates pager links as plain href links. Here’s what the output looks like: <div id="ItemPager" class="pagercontainer"> <div class="pager"> <span class="pagertext">Pages: </span><a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=1" class="pagerbutton" />1</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=2" class="pagerbutton" />2</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=3" class="pagerbutton" />3</a> <span class="pagerbutton-selected">4</span> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=5" class="pagerbutton" />5</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=6" class="pagerbutton" />6</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=20" class="pagerbutton pagerbutton-last" />20</a>&nbsp;<a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=3" class="pagerbutton pagerbutton-prev" />Prev</a>&nbsp;<a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=5" class="pagerbutton pagerbutton-next" />Next</a></div> <br clear="all" /> </div> </div> The links point back to the current page and simply append a Page= page link into the page. When the page gets reloaded with the new page number the pager automatically detects the page number and automatically assigns the ActivePage property which results in the appropriate page to be displayed. The code shown in the previous section is all that’s needed to handle paging. Note that HTTP GET based paging is different than the Postback paging ASP.NET uses by default. Postback paging preserves modified page content when clicking on pager buttons, but this control will simply load a new page – no page preservation at this time. The advantage of not using Postback paging is that the URLs generated are plain HTML links that a search engine can follow where __doPostback() links are not. Pager with a Grid The pager also works in combination with grid controls so it’s easy to bypass the grid control’s paging features if desired. In the following example I use a gridView control and binds it to a DataTable result which is also filterable by the Pager control. The very basic plain vanilla ASP.NET grid markup looks like this: <div style="width: 600px; margin: 0 auto;padding: 20px; "> <asp:DataGrid runat="server" AutoGenerateColumns="True" ID="gdItems" CssClass="blackborder" style="width: 600px;"> <AlternatingItemStyle CssClass="gridalternate" /> <HeaderStyle CssClass="gridheader" /> </asp:DataGrid> <ww:Pager runat="server" ID="Pager" CssClass="gridpager" ContainerDivCssClass="gridpagercontainer" PageLinkCssClass="gridpagerbutton" SelectedPageCssClass="gridpagerbutton-selected" PageSize="8" RenderContainerDiv="true" MaxPagesToDisplay="6" /> </div> and looks like this when rendered: using custom set of CSS styles. The code behind for this code is also very simple: protected void Page_Load(object sender, EventArgs e) { string category = Request.Params["category"] ?? ""; busItem itemRep = WebStoreFactory.GetItem(); var items = itemRep.GetItemsByCategory(category) .Select(itm => new {Sku = itm.Sku, Description = itm.Description}); // run query into a DataTable for demonstration DataTable dt = itemRep.Converter.ToDataTable(items,"TItems"); // Remove all items not on the current page dt = Pager.FilterDataTable(dt,0); // bind and display gdItems.DataSource = dt; gdItems.DataBind(); } A little contrived I suppose since the list could already be bound from the list of elements, but this is to demonstrate that you can also bind against a DataTable if your business layer returns those. Unfortunately there’s no way to filter a DataReader as it’s a one way forward only reader and the reader is required by the DataSource to perform the bindings.  However, you can still use a DataReader as long as your business logic filters the data prior to rendering and provides a total item count (most likely as a second query). Control Creation The control itself is a pretty brute force ASP.NET control. Nothing clever about this other than some basic rendering logic and some simple calculations and update routines to determine which buttons need to be shown. You can take a look at the full code from the West Wind Web Toolkit’s Repository (note there are a few dependencies). To give you an idea how the control works here is the Render() method: /// <summary> /// overridden to handle custom pager rendering for runtime and design time /// </summary> /// <param name="writer"></param> protected override void Render(HtmlTextWriter writer) { base.Render(writer); if (TotalPages == 0 && TotalItems > 0) TotalPages = CalculateTotalPagesFromTotalItems(); if (DesignMode) TotalPages = 10; // don't render pager if there's only one page if (TotalPages < 2) return; if (RenderContainerDiv) { if (!string.IsNullOrEmpty(ContainerDivCssClass)) writer.AddAttribute("class", ContainerDivCssClass); writer.RenderBeginTag("div"); } // main pager wrapper writer.WriteBeginTag("div"); writer.AddAttribute("id", this.ClientID); if (!string.IsNullOrEmpty(CssClass)) writer.WriteAttribute("class", this.CssClass); writer.Write(HtmlTextWriter.TagRightChar + "\r\n"); // Pages Text writer.WriteBeginTag("span"); if (!string.IsNullOrEmpty(PagesTextCssClass)) writer.WriteAttribute("class", PagesTextCssClass); writer.Write(HtmlTextWriter.TagRightChar); writer.Write(this.PagesText); writer.WriteEndTag("span"); // if the base url is empty use the current URL FixupBaseUrl(); // set _startPage and _endPage ConfigurePagesToRender(); // write out first page link if (ShowFirstAndLastPageLinks && _startPage != 1) { writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, (1).ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-first"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write("1"); writer.WriteEndTag("a"); writer.Write("&nbsp;"); } // write out all the page links for (int i = _startPage; i < _endPage + 1; i++) { if (i == ActivePage) { writer.WriteBeginTag("span"); if (!string.IsNullOrEmpty(SelectedPageCssClass)) writer.WriteAttribute("class", SelectedPageCssClass); writer.Write(HtmlTextWriter.TagRightChar); writer.Write(i.ToString()); writer.WriteEndTag("span"); } else { writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, i.ToString()).TrimEnd('&'); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(i.ToString()); writer.WriteEndTag("a"); } writer.Write("\r\n"); } // write out last page link if (ShowFirstAndLastPageLinks && _endPage < TotalPages) { writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, TotalPages.ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-last"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(TotalPages.ToString()); writer.WriteEndTag("a"); } // Previous link if (ShowPreviousNextLinks && !string.IsNullOrEmpty(PreviousText) && ActivePage > 1) { writer.Write("&nbsp;"); writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, (ActivePage - 1).ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-prev"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(PreviousText); writer.WriteEndTag("a"); } // Next link if (ShowPreviousNextLinks && !string.IsNullOrEmpty(NextText) && ActivePage < TotalPages) { writer.Write("&nbsp;"); writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, (ActivePage + 1).ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-next"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(NextText); writer.WriteEndTag("a"); } writer.WriteEndTag("div"); if (RenderContainerDiv) { if (RenderContainerDivBreak) writer.Write("<br clear=\"all\" />\r\n"); writer.WriteEndTag("div"); } } As I said pretty much brute force rendering based on the control’s property settings of which there are quite a few: You can also see the pager in the designer above. unfortunately the VS designer (both 2010 and 2008) fails to render the float: left CSS styles properly and starts wrapping after margins are applied in the special buttons. Not a big deal since VS does at least respect the spacing (the floated elements overlay). Then again I’m not using the designer anyway :-}. Filtering Data What makes the Pager easy to use is the filter methods built into the control. While this functionality is clearly not the most politically correct design choice as it violates separation of concerns, it’s very useful for typical pager operation. While I actually have filter methods that do something similar in my business layer, having it exposed on the control makes the control a lot more useful for typical databinding scenarios. Of course these methods are optional – if you have a business layer that can provide filtered page queries for you can use that instead and assign the TotalItems property manually. There are three filter method types available for IQueryable, IEnumerable and for DataTable which tend to be the most common use cases in my apps old and new. The IQueryable version is pretty simple as it can simply rely on on .Skip() and .Take() with LINQ: /// <summary> /// <summary> /// Queries the database for the ActivePage applied manually /// or from the Request["page"] variable. This routine /// figures out and sets TotalPages, ActivePage and /// returns a filtered subset IQueryable that contains /// only the items from the ActivePage. /// </summary> /// <param name="query"></param> /// <param name="activePage"> /// The page you want to display. Sets the ActivePage property when passed. /// Pass 0 or smaller to use ActivePage setting. /// </param> /// <returns></returns> public IQueryable<T> FilterIQueryable<T>(IQueryable<T> query, int activePage) where T : class, new() { ActivePage = activePage < 1 ? ActivePage : activePage; if (ActivePage < 1) ActivePage = 1; TotalItems = query.Count(); if (TotalItems <= PageSize) { ActivePage = 1; TotalPages = 1; return query; } int skip = ActivePage - 1; if (skip > 0) query = query.Skip(skip * PageSize); _TotalPages = CalculateTotalPagesFromTotalItems(); return query.Take(PageSize); } The IEnumerable<T> version simply  converts the IEnumerable to an IQuerable and calls back into this method for filtering. The DataTable version requires a little more work to manually parse and filter records (I didn’t want to add the Linq DataSetExtensions assembly just for this): /// <summary> /// Filters a data table for an ActivePage. /// /// Note: Modifies the data set permanently by remove DataRows /// </summary> /// <param name="dt">Full result DataTable</param> /// <param name="activePage">Page to display. 0 to use ActivePage property </param> /// <returns></returns> public DataTable FilterDataTable(DataTable dt, int activePage) { ActivePage = activePage < 1 ? ActivePage : activePage; if (ActivePage < 1) ActivePage = 1; TotalItems = dt.Rows.Count; if (TotalItems <= PageSize) { ActivePage = 1; TotalPages = 1; return dt; } int skip = ActivePage - 1; if (skip > 0) { for (int i = 0; i < skip * PageSize; i++ ) dt.Rows.RemoveAt(0); } while(dt.Rows.Count > PageSize) dt.Rows.RemoveAt(PageSize); return dt; } Using the Pager Control The pager as it is is a first cut I built a couple of weeks ago and since then have been tweaking a little as part of an internal project I’m working on. I’ve replaced a bunch of pagers on various older pages with this pager without any issues and have what now feels like a more consistent user interface where paging looks and feels the same across different controls. As a bonus I’m only loading the data from the database that I need to display a single page. With the preset class tags applied too adding a pager is now as easy as dropping the control and adding the style sheet for styling to be consistent – no fuss, no muss. Schweet. Hopefully some of you may find this as useful as I have or at least as a baseline to build ontop of… Resources The Pager is part of the West Wind Web & Ajax Toolkit Pager.cs Source Code (some toolkit dependencies) Westwind.css base stylesheet with .pager and .gridpager styles Pager Example Page © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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  • Using HTML 5 SessionState to save rendered Page Content

    - by Rick Strahl
    HTML 5 SessionState and LocalStorage are very useful and super easy to use to manage client side state. For building rich client side or SPA style applications it's a vital feature to be able to cache user data as well as HTML content in order to swap pages in and out of the browser's DOM. What might not be so obvious is that you can also use the sessionState and localStorage objects even in classic server rendered HTML applications to provide caching features between pages. These APIs have been around for a long time and are supported by most relatively modern browsers and even all the way back to IE8, so you can use them safely in your Web applications. SessionState and LocalStorage are easy The APIs that make up sessionState and localStorage are very simple. Both object feature the same API interface which  is a simple, string based key value store that has getItem, setItem, removeitem, clear and  key methods. The objects are also pseudo array objects and so can be iterated like an array with  a length property and you have array indexers to set and get values with. Basic usage  for storing and retrieval looks like this (using sessionStorage, but the syntax is the same for localStorage - just switch the objects):// set var lastAccess = new Date().getTime(); if (sessionStorage) sessionStorage.setItem("myapp_time", lastAccess.toString()); // retrieve in another page or on a refresh var time = null; if (sessionStorage) time = sessionStorage.getItem("myapp_time"); if (time) time = new Date(time * 1); else time = new Date(); sessionState stores data that is browser session specific and that has a liftetime of the active browser session or window. Shut down the browser or tab and the storage goes away. localStorage uses the same API interface, but the lifetime of the data is permanently stored in the browsers storage area until deleted via code or by clearing out browser cookies (not the cache). Both sessionStorage and localStorage space is limited. The spec is ambiguous about this - supposedly sessionStorage should allow for unlimited size, but it appears that most WebKit browsers support only 2.5mb for either object. This means you have to be careful what you store especially since other applications might be running on the same domain and also use the storage mechanisms. That said 2.5mb worth of character data is quite a bit and would go a long way. The easiest way to get a feel for how sessionState and localStorage work is to look at a simple example. You can go check out the following example online in Plunker: http://plnkr.co/edit/0ICotzkoPjHaWa70GlRZ?p=preview which looks like this: Plunker is an online HTML/JavaScript editor that lets you write and run Javascript code and similar to JsFiddle, but a bit cleaner to work in IMHO (thanks to John Papa for turning me on to it). The sample has two text boxes with counts that update session/local storage every time you click the related button. The counts are 'cached' in Session and Local storage. The point of these examples is that both counters survive full page reloads, and the LocalStorage counter survives a complete browser shutdown and restart. Go ahead and try it out by clicking the Reload button after updating both counters and then shutting down the browser completely and going back to the same URL (with the same browser). What you should see is that reloads leave both counters intact at the counted values, while a browser restart will leave only the local storage counter intact. The code to deal with the SessionStorage (and LocalStorage not shown here) in the example is isolated into a couple of wrapper methods to simplify the code: function getSessionCount() { var count = 0; if (sessionStorage) { var count = sessionStorage.getItem("ss_count"); count = !count ? 0 : count * 1; } $("#txtSession").val(count); return count; } function setSessionCount(count) { if (sessionStorage) sessionStorage.setItem("ss_count", count.toString()); } These two functions essentially load and store a session counter value. The two key methods used here are: sessionStorage.getItem(key); sessionStorage.setItem(key,stringVal); Note that the value given to setItem and return by getItem has to be a string. If you pass another type you get an error. Don't let that limit you though - you can easily enough store JSON data in a variable so it's quite possible to pass complex objects and store them into a single sessionStorage value:var user = { name: "Rick", id="ricks", level=8 } sessionStorage.setItem("app_user",JSON.stringify(user)); to retrieve it:var user = sessionStorage.getItem("app_user"); if (user) user = JSON.parse(user); Simple! If you're using the Chrome Developer Tools (F12) you can also check out the session and local storage state on the Resource tab:   You can also use this tool to refresh or remove entries from storage. What we just looked at is a purely client side implementation where a couple of counters are stored. For rich client centric AJAX applications sessionStorage and localStorage provide a very nice and simple API to store application state while the application is running. But you can also use these storage mechanisms to manage server centric HTML applications when you combine server rendering with some JavaScript to perform client side data caching. You can both store some state information and data on the client (ie. store a JSON object and carry it forth between server rendered HTML requests) or you can use it for good old HTTP based caching where some rendered HTML is saved and then restored later. Let's look at the latter with a real life example. Why do I need Client-side Page Caching for Server Rendered HTML? I don't know about you, but in a lot of my existing server driven applications I have lists that display a fair amount of data. Typically these lists contain links to then drill down into more specific data either for viewing or editing. You can then click on a link and go off to a detail page that provides more concise content. So far so good. But now you're done with the detail page and need to get back to the list, so you click on a 'bread crumbs trail' or an application level 'back to list' button and… …you end up back at the top of the list - the scroll position, the current selection in some cases even filters conditions - all gone with the wind. You've left behind the state of the list and are starting from scratch in your browsing of the list from the top. Not cool! Sound familiar? This a pretty common scenario with server rendered HTML content where it's so common to display lists to drill into, only to lose state in the process of returning back to the original list. Look at just about any traditional forums application, or even StackOverFlow to see what I mean here. Scroll down a bit to look at a post or entry, drill in then use the bread crumbs or tab to go back… In some cases returning to the top of a list is not a big deal. On StackOverFlow that sort of works because content is turning around so quickly you probably want to actually look at the top posts. Not always though - if you're browsing through a list of search topics you're interested in and drill in there's no way back to that position. Essentially anytime you're actively browsing the items in the list, that's when state becomes important and if it's not handled the user experience can be really disrupting. Content Caching If you're building client centric SPA style applications this is a fairly easy to solve problem - you tend to render the list once and then update the page content to overlay the detail content, only hiding the list temporarily until it's used again later. It's relatively easy to accomplish this simply by hiding content on the page and later making it visible again. But if you use server rendered content, hanging on to all the detail like filters, selections and scroll position is not quite as easy. Or is it??? This is where sessionStorage comes in handy. What if we just save the rendered content of a previous page, and then restore it when we return to this page based on a special flag that tells us to use the cached version? Let's see how we can do this. A real World Use Case Recently my local ISP asked me to help out with updating an ancient classifieds application. They had a very busy, local classifieds app that was originally an ASP classic application. The old app was - wait for it: frames based - and even though I lobbied against it, the decision was made to keep the frames based layout to allow rapid browsing of the hundreds of posts that are made on a daily basis. The primary reason they wanted this was precisely for the ability to quickly browse content item by item. While I personally hate working with Frames, I have to admit that the UI actually works well with the frames layout as long as you're running on a large desktop screen. You can check out the frames based desktop site here: http://classifieds.gorge.net/ However when I rebuilt the app I also added a secondary view that doesn't use frames. The main reason for this of course was for mobile displays which work horribly with frames. So there's a somewhat mobile friendly interface to the interface, which ditches the frames and uses some responsive design tweaking for mobile capable operation: http://classifeds.gorge.net/mobile  (or browse the base url with your browser width under 800px)   Here's what the mobile, non-frames view looks like:   As you can see this means that the list of classifieds posts now is a list and there's a separate page for drilling down into the item. And of course… originally we ran into that usability issue I mentioned earlier where the browse, view detail, go back to the list cycle resulted in lost list state. Originally in mobile mode you scrolled through the list, found an item to look at and drilled in to display the item detail. Then you clicked back to the list and BAM - you've lost your place. Because there are so many items added on a daily basis the full list is never fully loaded, but rather there's a "Load Additional Listings"  entry at the button. Not only did we originally lose our place when coming back to the list, but any 'additionally loaded' items are no longer there because the list was now rendering  as if it was the first page hit. The additional listings, and any filters, the selection of an item all were lost. Major Suckage! Using Client SessionStorage to cache Server Rendered Content To work around this problem I decided to cache the rendered page content from the list in SessionStorage. Anytime the list renders or is updated with Load Additional Listings, the page HTML is cached and stored in Session Storage. Any back links from the detail page or the login or write entry forms then point back to the list page with a back=true query string parameter. If the server side sees this parameter it doesn't render the part of the page that is cached. Instead the client side code retrieves the data from the sessionState cache and simply inserts it into the page. It sounds pretty simple, and the overall the process is really easy, but there are a few gotchas that I'll discuss in a minute. But first let's look at the implementation. Let's start with the server side here because that'll give a quick idea of the doc structure. As I mentioned the server renders data from an ASP.NET MVC view. On the list page when returning to the list page from the display page (or a host of other pages) looks like this: https://classifieds.gorge.net/list?back=True The query string value is a flag, that indicates whether the server should render the HTML. Here's what the top level MVC Razor view for the list page looks like:@model MessageListViewModel @{ ViewBag.Title = "Classified Listing"; bool isBack = !string.IsNullOrEmpty(Request.QueryString["back"]); } <form method="post" action="@Url.Action("list")"> <div id="SizingContainer"> @if (!isBack) { @Html.Partial("List_CommandBar_Partial", Model) <div id="PostItemContainer" class="scrollbox" xstyle="-webkit-overflow-scrolling: touch;"> @Html.Partial("List_Items_Partial", Model) @if (Model.RequireLoadEntry) { <div class="postitem loadpostitems" style="padding: 15px;"> <div id="LoadProgress" class="smallprogressright"></div> <div class="control-progress"> Load additional listings... </div> </div> } </div> } </div> </form> As you can see the query string triggers a conditional block that if set is simply not rendered. The content inside of #SizingContainer basically holds  the entire page's HTML sans the headers and scripts, but including the filter options and menu at the top. In this case this makes good sense - in other situations the fact that the menu or filter options might be dynamically updated might make you only cache the list rather than essentially the entire page. In this particular instance all of the content works and produces the proper result as both the list along with any filter conditions in the form inputs are restored. Ok, let's move on to the client. On the client there are two page level functions that deal with saving and restoring state. Like the counter example I showed earlier, I like to wrap the logic to save and restore values from sessionState into a separate function because they are almost always used in several places.page.saveData = function(id) { if (!sessionStorage) return; var data = { id: id, scroll: $("#PostItemContainer").scrollTop(), html: $("#SizingContainer").html() }; sessionStorage.setItem("list_html",JSON.stringify(data)); }; page.restoreData = function() { if (!sessionStorage) return; var data = sessionStorage.getItem("list_html"); if (!data) return null; return JSON.parse(data); }; The data that is saved is an object which contains an ID which is the selected element when the user clicks and a scroll position. These two values are used to reset the scroll position when the data is used from the cache. Finally the html from the #SizingContainer element is stored, which makes for the bulk of the document's HTML. In this application the HTML captured could be a substantial bit of data. If you recall, I mentioned that the server side code renders a small chunk of data initially and then gets more data if the user reads through the first 50 or so items. The rest of the items retrieved can be rather sizable. Other than the JSON deserialization that's Ok. Since I'm using SessionStorage the storage space has no immediate limits. Next is the core logic to handle saving and restoring the page state. At first though this would seem pretty simple, and in some cases it might be, but as the following code demonstrates there are a few gotchas to watch out for. Here's the relevant code I use to save and restore:$( function() { … var isBack = getUrlEncodedKey("back", location.href); if (isBack) { // remove the back key from URL setUrlEncodedKey("back", "", location.href); var data = page.restoreData(); // restore from sessionState if (!data) { // no data - force redisplay of the server side default list window.location = "list"; return; } $("#SizingContainer").html(data.html); var el = $(".postitem[data-id=" + data.id + "]"); $(".postitem").removeClass("highlight"); el.addClass("highlight"); $("#PostItemContainer").scrollTop(data.scroll); setTimeout(function() { el.removeClass("highlight"); }, 2500); } else if (window.noFrames) page.saveData(null); // save when page loads $("#SizingContainer").on("click", ".postitem", function() { var id = $(this).attr("data-id"); if (!id) return true; if (window.noFrames) page.saveData(id); var contentFrame = window.parent.frames["Content"]; if (contentFrame) contentFrame.location.href = "show/" + id; else window.location.href = "show/" + id; return false; }); … The code starts out by checking for the back query string flag which triggers restoring from the client cache. If cached the cached data structure is read from sessionStorage. It's important here to check if data was returned. If the user had back=true on the querystring but there is no cached data, he likely bookmarked this page or otherwise shut down the browser and came back to this URL. In that case the server didn't render any detail and we have no cached data, so all we can do is redirect to the original default list view using window.location. If we continued the page would render no data - so make sure to always check the cache retrieval result. Always! If there is data the it's loaded and the data.html data is restored back into the document by simply injecting the HTML back into the document's #SizingContainer element:$("#SizingContainer").html(data.html); It's that simple and it's quite quick even with a fully loaded list of additional items and on a phone. The actual HTML data is stored to the cache on every page load initially and then again when the user clicks on an element to navigate to a particular listing. The former ensures that the client cache always has something in it, and the latter updates with additional information for the selected element. For the click handling I use a data-id attribute on the list item (.postitem) in the list and retrieve the id from that. That id is then used to navigate to the actual entry as well as storing that Id value in the saved cached data. The id is used to reset the selection by searching for the data-id value in the restored elements. The overall process of this save/restore process is pretty straight forward and it doesn't require a bunch of code, yet it yields a huge improvement in the usability of the site on mobile devices (or anybody who uses the non-frames view). Some things to watch out for As easy as it conceptually seems to simply store and retrieve cached content, you have to be quite aware what type of content you are caching. The code above is all that's specific to cache/restore cycle and it works, but it took a few tweaks to the rest of the script code and server code to make it all work. There were a few gotchas that weren't immediately obvious. Here are a few things to pay attention to: Event Handling Logic Timing of manipulating DOM events Inline Script Code Bookmarking to the Cache Url when no cache exists Do you have inline script code in your HTML? That script code isn't going to run if you restore from cache and simply assign or it may not run at the time you think it would normally in the DOM rendering cycle. JavaScript Event Hookups The biggest issue I ran into with this approach almost immediately is that originally I had various static event handlers hooked up to various UI elements that are now cached. If you have an event handler like:$("#btnSearch").click( function() {…}); that works fine when the page loads with server rendered HTML, but that code breaks when you now load the HTML from cache. Why? Because the elements you're trying to hook those events to may not actually be there - yet. Luckily there's an easy workaround for this by using deferred events. With jQuery you can use the .on() event handler instead:$("#SelectionContainer").on("click","#btnSearch", function() {…}); which monitors a parent element for the events and checks for the inner selector elements to handle events on. This effectively defers to runtime event binding, so as more items are added to the document bindings still work. For any cached content use deferred events. Timing of manipulating DOM Elements Along the same lines make sure that your DOM manipulation code follows the code that loads the cached content into the page so that you don't manipulate DOM elements that don't exist just yet. Ideally you'll want to check for the condition to restore cached content towards the top of your script code, but that can be tricky if you have components or other logic that might not all run in a straight line. Inline Script Code Here's another small problem I ran into: I use a DateTime Picker widget I built a while back that relies on the jQuery date time picker. I also created a helper function that allows keyboard date navigation into it that uses JavaScript logic. Because MVC's limited 'object model' the only way to embed widget content into the page is through inline script. This code broken when I inserted the cached HTML into the page because the script code was not available when the component actually got injected into the page. As the last bullet - it's a matter of timing. There's no good work around for this - in my case I pulled out the jQuery date picker and relied on native <input type="date" /> logic instead - a better choice these days anyway, especially since this view is meant to be primarily to serve mobile devices which actually support date input through the browser (unlike desktop browsers of which only WebKit seems to support it). Bookmarking Cached Urls When you cache HTML content you have to make a decision whether you cache on the client and also not render that same content on the server. In the Classifieds app I didn't render server side content so if the user comes to the page with back=True and there is no cached content I have to a have a Plan B. Typically this happens when somebody ends up bookmarking the back URL. The easiest and safest solution for this scenario is to ALWAYS check the cache result to make sure it exists and if not have a safe URL to go back to - in this case to the plain uncached list URL which amounts to effectively redirecting. This seems really obvious in hindsight, but it's easy to overlook and not see a problem until much later, when it's not obvious at all why the page is not rendering anything. Don't use <body> to replace Content Since we're practically replacing all the HTML in the page it may seem tempting to simply replace the HTML content of the <body> tag. Don't. The body tag usually contains key things that should stay in the page and be there when it loads. Specifically script tags and elements and possibly other embedded content. It's best to create a top level DOM element specifically as a placeholder container for your cached content and wrap just around the actual content you want to replace. In the app above the #SizingContainer is that container. Other Approaches The approach I've used for this application is kind of specific to the existing server rendered application we're running and so it's just one approach you can take with caching. However for server rendered content caching this is a pattern I've used in a few apps to retrofit some client caching into list displays. In this application I took the path of least resistance to the existing server rendering logic. Here are a few other ways that come to mind: Using Partial HTML Rendering via AJAXInstead of rendering the page initially on the server, the page would load empty and the client would render the UI by retrieving the respective HTML and embedding it into the page from a Partial View. This effectively makes the initial rendering and the cached rendering logic identical and removes the server having to decide whether this request needs to be rendered or not (ie. not checking for a back=true switch). All the logic related to caching is made on the client in this case. Using JSON Data and Client RenderingThe hardcore client option is to do the whole UI SPA style and pull data from the server and then use client rendering or databinding to pull the data down and render using templates or client side databinding with knockout/angular et al. As with the Partial Rendering approach the advantage is that there's no difference in the logic between pulling the data from cache or rendering from scratch other than the initial check for the cache request. Of course if the app is a  full on SPA app, then caching may not be required even - the list could just stay in memory and be hidden and reactivated. I'm sure there are a number of other ways this can be handled as well especially using  AJAX. AJAX rendering might simplify the logic, but it also complicates search engine optimization since there's no content loaded initially. So there are always tradeoffs and it's important to look at all angles before deciding on any sort of caching solution in general. State of the Session SessionState and LocalStorage are easy to use in client code and can be integrated even with server centric applications to provide nice caching features of content and data. In this post I've shown a very specific scenario of storing HTML content for the purpose of remembering list view data and state and making the browsing experience for lists a bit more friendly, especially if there's dynamically loaded content involved. If you haven't played with sessionStorage or localStorage I encourage you to give it a try. There's a lot of cool stuff that you can do with this beyond the specific scenario I've covered here… Resources Overview of localStorage (also applies to sessionStorage) Web Storage Compatibility Modernizr Test Suite© Rick Strahl, West Wind Technologies, 2005-2013Posted in JavaScript  HTML5  ASP.NET  MVC   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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