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• Getting browser to make an AJAX call ASAP, while page is still loading

  - by Chris

  I'm looking for tips on how to get the browser to kick off an AJAX call as soon as possible into processing a web page, ideally before the page is fully downloaded. Here's my approximate motivation: I have a web page that takes, say, 5 seconds to load. It calls a web service that takes, say, 10 seconds to load. If loading the page and calling the web service happened sequentially, the user would have to wait 15 seconds to see all the information. However, if I can get the web service call started before the 5 second page load is complete, then at least some of the work can happened in parallel. Ideally I'd like as much of the work to happen in parallel as possible. My initial theory was that I should place the AJAX-calling javascript as high up as possible in the web page HTML source (being mindful of putting it after the jquery.js include, because I'm making the call using jquery ajax). I'm also being mindful not to wrap the AJAX call in a jquery ready event handler. (I mention this because ready events are popular in a lot of jquery example code.) However, the AJAX call still doesn't seem to get kicked off as early as I'm hoping (at least as judged by the Google Chrome "Timeline" feature), so I'm wondering what other considerations apply. One thing that might potentially be detrimental is that the AJAX call is back to the same web server that's serving the original web page, so I might be in danger of hitting a browser limit on the # of HTTP connections back to that one machine? (The HTML page loads a number of images, css files, etc..)

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• Can I embed a custom font in an iPhone application?

  - by Airsource Ltd

  I would like to have an app include a custom font for rendering text, load it, and then use it with standard UIKit elements like UILabel. Is this possible? I found these links: http://discussions.apple.com/thread.jspa?messageID=8304744 http://forums.macrumors.com/showthread.php?t=569311 but these would require me to render each glyph myself, which is a bit too much like hard work, especially for multi-line text. I've also found posts that say straight out that it's not possible, but without justification, so I'm looking for a definitive answer. EDIT - failed -[UIFont fontWithName:size:] experiment I downloaded Harrowprint.tff (downloaded from here) and added it to my Resources directory and to the project. I then tried this code: UIFont* font = [UIFont fontWithName:@"Harrowprint" size:20]; which resulted in an exception being thrown. Looking at the TTF file in Finder confirmed that the font name was Harrowprint. EDIT - there have been a number of replies so far which tell me to read the documentation on X or Y. I've experimented extensively with all of these, and got nowhere. In one case, X turned out to be relevant only on OS X, not on iPhone. Consequently I am setting a bounty for this question, and I will award the bounty to the first person who provides an answer (using only documented APIs) who responds with sufficient information to get this working on the device. Working on the simulator too would be a bonus. EDIT - it appears that the bounty auto-awards to the answer with the highest nunber of votes. Interesting. No one actually provided an answer that solved the question as asked - the solution that involves coding your own UILabel subclass doesn't support word-wrap, which is an essential feature for me - though I guess I could extend it to do so.

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• How to deal with calculated values with Dependency Properties on a custom WPF control

  - by jpierson

  To summarize what I'm doing, I have a custom control that looks like a checked listbox and that has two dependency properties one that provides a list of available options and the other that represents a enum flag value that combines the selection options. So as I mentioned my custom control exposes two different DependencyProperties, one of which is a list of options called Options and the other property called SelectedOptions is of a specific Enum type that uses the [Flags] attribute to allow combinations of values to be set. My UserControl then contains an ItemsControl similar to a ListBox that is used to display the options along with a checkbox. When the check box is checked or unchecked the SelectedOptions property should be updated accordingly by using the corresponding bitwise operation. The problem I'm experiencing is that I have no way other than resorting to maintaining private fields and handling property change events to update my properties which just feels unatural in WPF. I have tried using ValueConverters but have run into the problem that I can't really using binding with the value converter binding so I would need to resort to hard coding my enum values as the ValueConverter parameter which is not acceptable. If anybody has seen a good example of how to do this sanely I would greatly appreciate any input. Side Note: This has been a problem I've had in the past too while trying to wrap my head around how dependency properties don't allow calculated or deferred values. Another example is when one may want to expose a property on a child control as a property on the parent. Most suggest in this case to use binding but that only works if the child controls property is a Dependency Property since placing the binding so that the target is the parent property it would be overwritten when the user of the parent control wants to set their own binding for that property.

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• Ruby metaclass madness

  - by t6d

  I'm stuck. I'm trying to dynamically define a class method and I can't wrap my head around the ruby metaclass model. Consider the following class: class Example def self.meta; (class << self; self; end); end def self.class_instance; self; end end Example.class_instance.class # => Class Example.meta.class # => Class Example.class_instance == Example # => true Example.class_instance == Example.meta # => false Obviously both methods return an instance of Class. But these two instances are not the same. They also have different ancestors: Example.meta.ancestors # => [Class, Module, Object, Kernel] Example.class_instance.ancestors # => [Example, Object, Kernel] Whats the point in making a difference between the metaclass and the class instance? I figured out, that I can send :define_method to the metaclass to dynamically define a method, but if I try to send it to the class instance it won't work. At least I could solve my problem, but I still want to understand why it is working this way.

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• How should I write Jquery Mobile app for browsers with and without javascript support?

  - by Adrian Grigore

  Hi, I'm trying to wrap my head around jQuery Mobile. My aim is to build a very fast application with a look and feel as close as possible to a native app (at least for modern devices). I understand there are two ways of navigating between pages: Loading each page as a separate page and linking to other pages with regular html anchors. Putting all (or many) pages on one single web page and navigating between them by means of javascript ($.mobile.changePage (method) and similar api functions. The first approach should work on all browsers, but performs quite poorly since there is a delay between each page transition. The second looks like it should be much faster, so I would definitely prefer this approach. But how would that work for mobile device browsers without javascript support? It certainly seems to violate jQuery Mobile's aim to provide a gracefully degraded experience for C-grade browsers. It looks to me like I need to implement my app twice, once optimized for browsers with javascript support, once for browsers without? Using may be another option, but that looks even more messy. What's the recommended way to approach this dilemma? Is there anything I have not noticed? Thanks, Adrian

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• Numpy: Sorting a multidimensional array by a multidimensional array

  - by JD Long

  Forgive me if this is redundant or super basic. I'm coming to Python/Numpy from R and having a hard time flipping things around in my head. I have a n dimensional array which I want to sort using another n dimensional array of index values. I know I could wrap this in a loop but it seems like there should be a really concise Numpyonic way of beating this into submission. Here's my example code to set up the problem where n=2: a1 = random.standard_normal(size=[2,5]) index = array([[0,1,2,4,3] , [0,1,2,3,4] ]) so now I have a 2 x 5 array of random numbers and a 2 x 5 index. I've read the help for take() about 10 times now but my brain is not groking it, obviously. I thought this might get me there: take(a1, index) array([[ 0.29589188, -0.71279375, -0.18154864, -1.12184984, 0.25698875], [ 0.29589188, -0.71279375, -0.18154864, 0.25698875, -1.12184984]]) but that's clearly reordering only the first element (I presume because of flattening). Any tips on how I get from where I am to a solution that sorts element 0 of a1 by element 0 of the index ... element n?

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• Unable to read in my custom .config section

  - by Pure.Krome

  Hi folks, NOTE: this is very very similar to this SO question, but I need some more help. i'm trying to make the following section in my .config file, but i get an exception when trying to access this section. .config file <configSections> <section name="foos" type="Ackbar.Mvc.Models.Foo.FooCollection, Ackbar.Mvc" requirePermission="false"/> <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler" requirePermission="false" /> </configSections> <foos> <add name="aaa" something="zzz"/> <add name="bbb" something="yyy"/> <add name="ccc" something="xxx"/> </foos> Ok, so this means i need to make two classes classes public class FooCollection : ConfigurationElementCollection { ... with my custom overrides, etc. ... } and public class FooElement : ConfigurationElement { [ConfigurationProperty("Name", IsRequired = true)] public string Name { .. } [ConfigurationProperty("Something ", IsRequired = true)] public string Something { .. } [ConfigurationProperty("IsDefault ", IsRequired = false, DefaultValue = false)] public bool IsDefault { .. } } Kewl. Now, when i do the following .... var whatever = ConfigurationManager.GetSection("foos") is throws the following exception :- An error occurred creating the configuration section handler for foos: Type 'Ackbar.Mvc.Models.Foos.FooCollection' does not inherit from 'System.Configuration.IConfigurationSectionHandler'. Can someone please help me? I don't want to wrap the collection INSIDE a parent section. Cheers :)

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• Objective-C memory model

  - by TofuBeer

  I am attempting to wrap my head around one part of the Objective-C memory model (specifically on the iPhone, so no GC). My background is C/C++/Java, and I am having an issue with the following bit of code (also wondering if I am doing this in an "Objective-C way" or not): - (NSSet *) retrieve { NSMutableSet *set; set = [NSMutableSet new]; // would normally fill the set in here with some data return ([set autorelease]); } - (void) test { NSSet *setA; NSSet *setB; setA = [self retrieve]; setB = [[self retrieve] retain]; [setA release]; [setB release]; } start EDIT Based on comments below, the updated retrieve method: - (NSSet *) retrieve { NSMutableSet *set; set = [[[NSMutableSet alloc] initWithCapacity:100] autorelease]; // would normally fill the set in here with some data return (set); } end EDIT The above code gives a warning for [setA release] "Incorrect decrement of the reference count of an object is not owned at this point by the caller". I though that the "new" set the reference count to 1. Then the "retain" call would add 1, and the "release" call would drop it by 1. Given that wouldn't setA have a reference count of 0 at the end and setB have a reference count of 1 at the end? From what I have figured out by trial and error, setB is correct, and there is no memory leak, but I'd like to understand why that is the case (what is wrong with my understanding of "new", "autorelease", "retain", and "release").

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• How do I create Document Fragments with Nokogiri?

  - by viatropos

  I have an html document like this: <div class="something"> <textarea name="another"/> <div class="nested"> <label>Nested Label</label> <input name="nested_input"/> </div> </div> I have gone through and modified some of the html tree by building it into a Nokogiri::HTML::Document like so: html = Nokogiri::HTML(IO.read("test.html")) html.children.each do ... Now I want to be able to extract the nested part into a document so I can apply a stylesheet to it, or so I can manipulate it as if it were like a Rails partial. Something like this: fragment = Nokogiri::HTML(html.xpath("//div[@class='nested']).first) Is there a way to do that? Such a way that when I output it, it doesn't wrap it in<html> tags and turn it into an HTML document, I just want HTML, no document. Is this possible?

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• Limit foreign key choices in select in an inline form in admin

  - by mightyhal

  Edited :-) Hopefully a bit clearer now. The logic is of the model is: A Building has many Rooms A Room may be inside another Room (a closet, for instance--ForeignKey on 'self') A Room can only in inside of another Room in the same building (this is the tricky part) Here's the code I have: #spaces/models.py from django.db import models class Building(models.Model): name=models.CharField(max_length=32) def __unicode__(self): return self.name class Room(models.Model): number=models.CharField(max_length=8) building=models.ForeignKey(Building) inside_room=models.ForeignKey('self',blank=True,null=True) def __unicode__(self): return self.number and: #spaces/admin.py from ex.spaces.models import Building, Room from django.contrib import admin class RoomAdmin(admin.ModelAdmin): pass class RoomInline(admin.TabularInline): model = Room extra = 2 class BuildingAdmin(admin.ModelAdmin): inlines=[RoomInline] admin.site.register(Building, BuildingAdmin) admin.site.register(Room) The inline will display only rooms in the current building (which is what I want). The problem, though, is that for the inside_room drop down, it displays all of the rooms in the Rooms table (including those in other buildings). In the inline of rooms, I need to limit the inside_room choices to only rooms which are in the current building being displayed by the main form. I can't figure out a way to do it with either a limit_choices_to in the model, nor can I figure out how exactly to override the admin's inline formset properly (I feel like I should be somehow create a custom inline form, pass the building_id of the main form to the custom inline, then limit the queryset for the field's choices based on that--but I just can't wrap my head around how to do it). Maybe this is too complex for the admin site, but it seems like something that would be generally useful... Thanks again for your help!

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• How can I write reusable Javascript?

  - by RenderIn

  I've started to wrap my functions inside of Objects, e.g.: var Search = { carSearch: function(color) { }, peopleSearch: function(name) { }, ... } This helps a lot with readability, but I continue to have issues with reusabilty. To be more specific, the difficulty is in two areas: Receiving parameters. A lot of times I will have a search screen with multiple input fields and a button that calls the javascript search function. I have to either put a bunch of code in the onclick of the button to retrieve and then martial the values from the input fields into the function call, or I have to hardcode the HTML input field names/IDs so that I can subsequently retrieve them with Javascript. The solution I've settled on for this is to pass the field names/IDs into the function, which it then uses to retrieve the values from the input fields. This is simple but really seems improper. Returning values. The effect of most Javascript calls tends to be one in which some visual on the screen changes directly, or as a result of another action performed in the call. Reusability is toast when I put these screen-altering effects at the end of a function. For example, after a search is completed I need to display the results on the screen. How do others handle these issues? Putting my thinking cap on leads me to believe that I need to have an page-specific layer of Javascript between each use in my application and the generic methods I create which are to be used application-wide. Using the previous example, I would have a search button whose onclick calls a myPageSpecificSearchFunction, in which the search field IDs/names are hardcoded, which marshals the parameters and calls the generic search function. The generic function would return data/objects/variables only, and would not directly read from or make any changes to the DOM. The page-specific search function would then receive this data back and alter the DOM appropriately. Am I on the right path or is there a better pattern to handle the reuse of Javascript objects/methods?

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• Jquery Tools: Scrollable - onBeforeSeek & onSeek toggle child div

  - by Rick

  I'm scrolling some panels which contain some youtube clips using Jquery Tools Scrollable. I'd like to hide them during the transition to avoid a jerky animation. Markup: <div id="panel_items"> <div id="wrap"> <div class="event"> <div class="header">Event 1</div><!-- Header is always displayed --> <div class="youtube">youtube clips</div><!-- hide during transition, then show --> </div> <div class="event"> <div class="header">Event 2</div> <div class="youtube" style="display: none">More youtube clips</div> </div> </div> </div> Current JS: $("#panel_items").scrollable({ onBeforeSeek: function() { console.log("hide .child .youtube"); }, onSeek: function() { console.log("Show child .youtube"); } }); Bonus question: How can I automatically set the height of #panel_items to match the current panel height (.event)? Thank you.

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• C++ Swig Python (Embedded Python in C++) works in Release but not in Debug

  - by sambha

  Platform: Windows 7, 64 bit (x64), Visual Studio 2008 I chose Python & Swig binding as the scripting environment of the application. As a prototype, created a simple VS solution with main() which initializes Python (Py_Initalize, Py_setPyHome, etc) & executes test.py. In the same solution created another project which is a DLL of a simple class. Used SWIG to wrap this class. This DLL is the _MyClasses.pyd. test.py creates the objects of my class & calls its member functions. All this works like a charm in the Release mode. But does not work in Debug mode (even tried banging my head on the laptop ;-) ). Output of my work looks like this (in both release & debug): x64 -debug - _MyClasses.pyd - MyClasses.py - test.exe - test.py - python26.dll - python26_d.dll Note that the debug version is linked against python26_d.lib. Had to build python myself for this! test.py import MyClasses print "ello" m = MyClasses.Male("John Doe", 25) print m.getType() Male is the C++ class. The problem: Traceback (most recent call last): File "test.py", line 6, in <module> import MyClasses File "...\x64\Debug\MyClasses.py", line 25, in <module> _MyClasses = swig_import_helper() File "...\x64\Debug\MyClasses.py", line 17, in swig_imp ort_helper import _MyClasses ImportError: No module named _MyClasses [15454 refs] I am used to Makefiles & am new to Visual Studio. I dont know who the culprit is here: Swig, The debug build of Python, Visual Studio, my stupidity. Thank you in advance. It will be a great help.

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• WPF DataValidation on a DataTemplate object in an ItemsControl

  - by Matt H.

  I have two datatemplates, both very similar... here is one of them: <DataTemplate x:Key="HeadingTemplate"> <Grid x:Name="mainHeadingGrid" Margin="5,5,30,0" HorizontalAlignment="Stretch"> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition /> </Grid.ColumnDefinitions> <TextBlock Grid.Column="1" Margin="30,3,10,0" Foreground="Black" FontWeight="Bold" HorizontalAlignment="Left" TextWrapping="Wrap"> <TextBlock.Text> <MultiBinding Converter="{StaticResource myHeadingConverter}" ConverterParameter="getRNHeadingTitle" Mode="TwoWay"> <Binding Path="num"/> <Binding Path="name"/> </MultiBinding> </TextBlock.Text> </TextBlock> <TextBox Grid.Column="1" Text="{Binding Path=moreInfo}"/> </Grid> </DataTemplate> I use an selector in my ItemsControl to choose between the two, based on the object it is bound to. I want to use validation to check through all of the properties and put a big exclamation point in front of the whole datatemplate as it is displayed in the itemscontrol. how do I do this? All of the examples I've found explain how to set a ValidationRule on a specific control in the datatemplate, in that control's binding. I want to apply my validation rule to the entire template... Help! :)

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• Trouble binding WPF Menu to ItemsSource

  - by chaiguy

  I would like to avoid having to build a menu manually in XAML or code, by binding to a list of ICommand-derived objects. However, I'm experiencing a bit of a problem where the resulting menu has two levels of menu-items (i.e. each MenuItem is contained in a MenuItem): My guess is that this is happening because WPF is automatically generating a MenuItem for my binding, but the "viewer" I'm using actually already is a MenuItem (it's derived from MenuItem): <ContextMenu x:Name="selectionContextMenu" ItemsSource="{Binding Source={x:Static OrangeNote:Note.MultiCommands}}" ItemContainerStyleSelector="{StaticResource separatorStyleSelector}"> <ContextMenu.ItemTemplate> <DataTemplate> <Viewers:NoteCommandMenuItemViewer CommandParameter="{Binding Source={x:Static OrangeNote:App.Screen}, Path=SelectedNotes}" /> </DataTemplate> </ContextMenu.ItemTemplate> </ContextMenu> (The ItemContainerStyleSelector is from http://bea.stollnitz.com/blog/?p=23, which allows me to have Separator elements inside my bound source.) So, the menu is bound to a collection of ICommands, and each item's CommandParameter is set to the same global target (which happens to be a collection, but that's not important). My question is, is there any way I can bind this such that WPF doesn't automatically wrap each item in a MenuItem?

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• Correct escaping of delimited identifers in SQL Server without using QUOTENAME

  - by Ross Bradbury

  Is there anything else that the code must do to sanitize identifiers (table, view, column) other than to wrap them in double quotation marks and "double up" and double quotation marks present in the identifier name? References would be appreciated. I have inherited a code base that has a custom object-relational mapping (ORM) system. SQL cannot be written in the application but the ORM must still eventually generate the SQL to send to the SQL Server. All identifiers are quoted with double quotation marks. string QuoteName(string identifier) { return "\" + identifier.Replace("\"", "\"\"") + "\""; } If I were building this dynamic SQL in SQL, I would use the built-in SQL Server QUOTENAME function: declare @identifier nvarchar(128); set @identifier = N'Client"; DROP TABLE [dbo].Client; --'; declare @delimitedIdentifier nvarchar(258); set @delimitedIdentifier = QUOTENAME(@identifier, '"'); print @delimitedIdentifier; -- "Client""; DROP TABLE [dbo].Client; --" I have not found any definitive documentation about how to escape quoted identifiers in SQL Server. I have found Delimited Identifiers (Database Engine) and I also saw this stackoverflow question about sanitizing. If it were to have to call the QUOTENAME function just to quote the identifiers that is a lot of traffic to SQL Server that should not be needed. The ORM seems to be pretty well thought out with regards to SQL Injection. It is in C# and predates the nHibernate port and Entity Framework etc. All user input is sent using ADO.NET SqlParameter objects, it is just the identifier names that I am concerned about in this question. This needs to work on SQL Server 2005 and 2008.

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• Get "term is undefined” error when trying to assign arrayList to List component dataSource

  - by user1814467

  I'm creating an online game where people log in and then have the list of current players displayed. When the user enters a "room" it dispatches an SFSEvent which includes a Room object with the list of users as User objects in that room. As that event's callback function, I get the list of current users which is an Array, switch the View Stack child index, and then I wrap the user list array in an ArrayList before I assign it to the MXML Spark List component's dataSource. Here's my code: My Actionscript Code Section (PreGame.as): private function onRoomJoin(event:SFSEvent):void { const room:Room = this._sfs.getRoomByName(PREGAME_ROOM); this.selectedChild = waitingRoom; /** I know I should be using event listeners * but this is a temporary fix, otherwise * I keep getting null object errors * do to the li_users list not being * created in time for the dataProvider assignment **/ setTimeout(function ():void { const userList:ArrayList = new ArrayList(room.userList); this.li_users.dataProvider = userList; // This is where the error gets thrown },1000); } My MXML Code: <?xml version="1.0" encoding="utf-8"?> <mx:ViewStack xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx" initialize="preGame_initializeHandler(event)" > <fx:Script source="PreGame.as"/> <s:NavigatorContent id="nc_loginScreen"> /** Login Screen Code **/ </s:NavigatorContent> /** Start of Waiting Room code **/ <s:NavigatorContent id="waitingRoom"> <s:Panel id="pn_users" width="400" height="400" title="Users"> /** This is the List in question **/ <s:List id="li_users" width="100%" height="100%"/> </s:Panel> </s:NavigatorContent> </mx:ViewStack> However, I keep getting this error: TypeError: Error #1010: A term is undefined and has no properties Any ideas what I'm doing wrong? The arrayList has data, so I know it's not empty/null.

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• Credit card system implementation?

  - by Mark

  My site is going to have a credit system that basically works a lot like a credit card. Each user has an unlimited credit limit, but at the end of each week, they have to pay it off. For example, a user might make several purchases between March 1st and 7th, and then at the end of March 7th, they would be emailed an invoice that lists all their purchases during the week and a total that is due by the 14th. If they don't pay it off, their account is simply deactivated until they do. I'm just trying to wrap my head around how to implement this. I have a list of all their purchases, that's not a problem, but I'm just trying to figure out what to do with it. On the end of the 7th day, I could set up a cronjob to generate an invoice, which would basically have an id, and due date, and then I would need another many-to-many table to link all the purchases to the invoice. Then when a user adds money to their account, I guess it's applied against their current outstanding invoice? And what if they don't pay off their invoice by the time a new invoice rolls around, so now they have 2 outstanding ones, how do I know which to apply it against? Or do I make the cronjob check for any previous outstanding invoices, cancel them, and add a new item to the new invoice as "balance forward (+interest)"? How would you apply the money against an invoice? Would each payment have to be linked to an invoice, or could I just deposit it to their account credit, and then somehow figure out whats been paid and what hasn't? What if they pay in advance, before their invoice has been generated? Do I deduct it from their credit from the invoice upon generation, or at the end of the week when its due? There are so many ways to do this... Can anyone describe what approach they would take?

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• Help! I've learned jQuery... now I want to learn JavaScript

  - by Derek Adair

  I am a self-taught web developer/programmer. I started out about two years ago by learning how to make simple dynamic websites with HTML/CSS/PHP. Then I started dabbling with animation... Enter jQuery I've become quite proficient with jQuery over the last year and I've even started making my own plugins. I've spent most of my effort learning how to beautify websites with fancy effects and what not. Upon tackling my first full-blown application, I realized how under-developed my knowledge of JavaScript actually is. jQuery has allowed me to rely on its framework so heavily that I rarely use any interesting functions, techniques, or whatever that are 'native' to the JavaScript language. For example: I have a basic understanding of what a closure is... but I am unsure where this technique can actually benefit me. Although as I understand it, that's what my jQuery plugins do with (function ($){//plugin code here})(jQuery). I've seen many posts/blogs/whatever about memory leaks and circular references which is concerning. I'm frustrated because I can wrap my head around the basic concepts of what these are just by reading the articles, but I'm finding that the deeper I go the more I don't understand. The vocabulary alone is burdensome. Let alone how to actually use these techniques/functions/language features. I am trying to figure out what I don't know I'm looking to gather any advice, techniques, articles, books, videos, snippets, examples, potential pitfalls... really anything you have regarding application development with JavaScript/jQuery.

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• Rails: Multiple "has_many through" for the two same models?

  - by neezer

  Can't wrap my head around this... class User < ActiveRecord::Base has_many :fantasies, :through => :fantasizings has_many :fantasizings, :dependent => :destroy end class Fantasy < ActiveRecord::Base has_many :users, :through => :fantasizings has_many :fantasizings, :dependent => :destroy end class Fantasizing < ActiveRecord::Base belongs_to :user belongs_to :fantasy end ... which works fine for my primary relationship, in that a User can have many Fantasies, and that a Fantasy can belong to many Users. However, I need to add another relationship for liking (as in, a User "likes" a Fantasy rather than "has" it... think of Facebook and how you can "like" a wall-post, even though it doesn't "belong" to you... in fact, the Facebook example is almost exactly what I'm aiming for). I gathered that I should make another association, but I'm kinda confused as to how I might use it, or if this is even the right approach. I started by adding the following: class Fantasy < ActiveRecord::Base ... has_many :users, :through => :approvals has_many :approvals, :dependent => :destroy end class User < ActiveRecord::Base ... has_many :fantasies, :through => :approvals has_many :approvals, :dependent => :destroy end class Approval < ActiveRecord::Base belongs_to :user belongs_to :fantasy end ... but how do I create the association through Approval rather than through Fantasizing? If someone could set me straight on this, I'd be much obliged!

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• Generic allocator class without variadic templates?

  - by rainer

  I am trying to write a generic allocator class that does not really release an object's memory when it is free()'d but holds it in a queue and returns a previously allocated object if a new one is requested. Now, what I can't wrap my head around is how to pass arguments to the object's constructor when using my allocator (at least without resorting to variadic templates, that is). The alloc() function i came up with looks like this: template <typename... T> inline T *alloc(const &T... args) { T *p; if (_free.empty()) { p = new T(args...); } else { p = _free.front(); _free.pop(); // to call the ctor of T, we need to first call its DTor p->~T(); p = new( p ) T(args...); } return p; } Still, I need the code to be compatible with today's C++ (and older versions of GCC that do not support variadic templates). Is there any other way to go about passing an arbitrary amount of arguments to the objects constructor?

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• Clojure agents consuming from a queue

  - by erikcw

  I'm trying to figure out the best way to use agents to consume items from a Message Queue (Amazon SQS). Right now I have a function (process-queue-item) that grabs an items from the queue, and processes it. I want to process these items concurrently, but I can't wrap my head around how to control the agents. Basically I want to keep all of the agents busy as much as possible without pulling to many items from the Queue and developing a backlog (I'll have this running on a couple of machines, so items need to be left in the queue until they are really needed). Can anyone give me some pointers on improving my implementation? (def active-agents (ref 0)) (defn process-queue-item [_] (dosync (alter active-agents inc)) ;retrieve item from Message Queue (Amazon SQS) and process (dosync (alter active-agents dec))) (defn -main [] (def agents (for [x (range 20)] (agent x))) (loop [loop-count 0] (if (< @active-agents 20) (doseq [agent agents] (if (agent-errors agent) (clear-agent-errors agent)) ;should skip this agent until later if it is still busy processing (not sure how) (send-off agent process-queue-item))) ;(apply await-for (* 10 1000) agents) (Thread/sleep 10000) (logging/info (str "ACTIVE AGENTS " @active-agents)) (if (> 10 loop-count) (do (logging/info (str "done, let's cleanup " count)) (doseq [agent agents] (if (agent-errors agent) (clear-agent-errors agent))) (apply await agents) (shutdown-agents)) (recur (inc count)))))

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• GWT forced height HTMLPanel

  - by Nils

  Hello, I'm developing a GWT project, and I encountered a problematic cross-browsering problem. When using firefox, there are problems with the display of all the pages. I found the reason why : In UIBinder, each of my pages are wrapped by a "g:HTMLPanel" : at start and at the end of the xml file, to wrap the content of all the pages When doing this, the generated code of the panel goes like this : div style="width: 100%; height: 100%; .... The problem is that "height : 100%". If I remove it with firebug, the display is perfect. So my goal is to programatically remove that generated 100% height.. But no way to do it ! I tried everything : setHeight, setSize, working on the Element itself with getElement().methods()... I tried to do things like style.clear(), everything that could have a chance to work.. But in the generated code that "height: 100%" will ALWAYS be there. If I set it's height to "50%" or "50px" it has no effect at all. I even tried to give it an ID, then with pure javascript to change it's style, but no solution either.. Note : I'm sure that I'm working on the right element : adding a styleName, for example, works well. Any idea ? Your help would be really appreciated, I have no clue of how to remove this bit of generated code, and I've been looking for hours already :(:(:(:( Best regards, Nils

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• Best approach to storing image pixels in bottom-up order in Java

  - by finnw

  I have an array of bytes representing an image in Windows BMP format and I would like my library to present it to the Java application as a BufferedImage, without copying the pixel data. The main problem is that all implementations of Raster in the JDK store image pixels in top-down, left-to-right order whereas BMP pixel data is stored bottom-up, left-to-right. If this is not compensated for, the resulting image will be flipped vertically. The most obvious "solution" is to set the SampleModel's scanlineStride property to a negative value and change the band offsets (or the DataBuffer's array offset) to point to the top-left pixel, i.e. the first pixel of the last line in the array. Unfortunately this does not work because all of the SampleModel constructors throw an exception if given a negative scanlineStride argument. I am currently working around it by forcing the scanlineStride field to a negative value using reflection, but I would like to do it in a cleaner and more portable way if possible. e.g. is there another way to fool the Raster or SampleModel into arranging the pixels in bottom-up order but without breaking encapsulation? Or is there a library somewhere that will wrap the Raster and SampleModel, presenting the pixel rows in reverse order? I would prefer to avoid the following approaches: Copying the whole image (for performance reasons. The code must process hundreds of large (= 1Mpixels) images per second and although the whole image must be available to the application, it will normally access only a tiny (but hard-to-predict) portion of the image.) Modifying the DataBuffer to perform coordinate transformation (this actually works but is another "dirty" solution because the buffer should not need to know about the scanline/pixel layout.) Re-implementing the Raster and/or SampleModel interfaces from scratch (but I have a hunch that I will be unable to avoid this.)

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• How do I do nested transactions in NHibernate?

  - by Gavin Schultz-Ohkubo

  Can I do nested transactions in NHibernate, and how do I implement them? I'm using SQL Server 2008, so support is definitely in the DBMS. I find that if I try something like this: using (var outerTX = UnitOfWork.Current.BeginTransaction()) { using (var nestedTX = UnitOfWork.Current.BeginTransaction()) { ... do stuff nestedTX.Commit(); } outerTX.Commit(); } then by the time it comes to outerTX.Commit() the transaction has become inactive, and results in a ObjectDisposedException on the session AdoTransaction. Are we therefore supposed to create nested NHibernate sessions instead? Or is there some other class we should use to wrap around the transactions (I've heard of TransactionScope, but I'm not sure what that is)? I'm now using Ayende's UnitOfWork implementation (thanks Sneal). Forgive any naivety in this question, I'm still new to NHibernate. Thanks! EDIT: I've discovered that you can use TransactionScope, such as: using (var transactionScope = new TransactionScope()) { using (var tx = UnitOfWork.Current.BeginTransaction()) { ... do stuff tx.Commit(); } using (var tx = UnitOfWork.Current.BeginTransaction()) { ... do stuff tx.Commit(); } transactionScope.Commit(); } However I'm not all that excited about this, as it locks us in to using SQL Server, and also I've found that if the database is remote then you have to worry about having MSDTC enabled... one more component to go wrong. Nested transactions are so useful and easy to do in SQL that I kind of assumed NHibernate would have some way of emulating the same...

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