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• what libraries or platforms should I use to build web apps that provide real-time, asynchronous data

  - by Daniel Sterling

  This is a less a question with a simple, practical answer and more a question to foster discussion on the real-time data exchange topic. I'll begin with an example: Google Wave is, at its core, a real-time asynchronous data synchronization engine. Wave supports (or plans to support) concurrent (real-time) document collaboration, disconnected (offline) document editing, conflict resolution, document history and playback with attribution, and server federation. A core part of Wave is the Operational Transformation engine: http://www.waveprotocol.org/whitepapers/operational-transform The OT engine manages document state. Changes between clients are merged and each client has a sane and consistent view of the document at all times; the final document is eventually consistent between all connected clients. My question is: is this system abstract or general enough to be used as a library or generic framework upon which to build web apps that synchronize real-time, asynchronous state in each client? Is the Wave protocol directly used by any current web applications (besides Google's client)? Would it make sense to directly use it for generic state synchronization in a web app? What other existing libraries or frameworks would you consider using when building such a web app? How much code in such an app might be domain-specific logic vs generic state synchronization logic? Or, put another way, how leaky might the state synchronization abstractions be? Comments and discussion welcomed!

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• Oracle - Getting Select Count(*) from ... as an output parameter in System.Data.OracleClient

  - by cbeuker

  Greetings all, I have a question. I am trying to build a parametrized query to get me the number of rows from a table in Oracle. Rather simple. However I am an Oracle newbie.. I know in SQL Server you can do something like: Select @outputVariable = count(*) from sometable where name = @SomeOtherVariable and then you can set up an Output parameter in the System.Data.SqlClient to get the @outputVariable. Thinking that one should be able to do this in Oracle as well, I have the following query Select count(*) into :theCount from sometable where name = :SomeValue I set up my oracle parameters (using System.Data.OracleClient - yes I know it will be deprecated in .Net 4 - but that's what I am working with for now) as follows IDbCommand command = new OracleCommand(); command.CommandText = "Select count(*) into :theCount from sometable where name = :SomeValue"); command.CommandType = CommandType.Text; OracleParameter parameterTheCount = new OracleParameter(":theCount ", OracleType.Number); parameterTheCount .Direction = ParameterDirection.Output; command.Parameters.Add(parameterTheCount ); OracleParameter parameterSomeValue = new OracleParameter(":SomeValue", OracleType.VarChar, 40); parameterSomeValue .Direction = ParameterDirection.Input; parameterSomeValue .Value = "TheValueToLookFor"; command.Parameters.Add(parameterSomeValue ); command.Connection = myconnectionObject; command.ExecuteNonQuery(); int theCount = (int)parameterTheCount.Value; At which point I was hoping the count would be in the parameter parameterTheCount that I could readily access. I keep getting the error ora-01036 which http://ora-01036.ora-code.com tells me to check my binding in the sql statement. Am I messing something up in the SQL statement? Am I missing something simple elsewhere? I could just use command.ExecuteScaler() as I am only getting one item, and am probably going to end up using that, but at this point, curiosity has got the better of me. What if I had two parameters I wanted back from my query (ie: select max(ColA), min(ColB) into :max, :min.....) Thanks..

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• How to restrict access to a class's data based on state?

  - by Marcus Swope

  In an ETL application I am working on, we have three basic processes: Validate and parse an XML file of customer information from a third party Match values received in the file to values in our system Load customer data in our system The issue here is that we may need to display the customer information from any or all of the above states to an internal user and there is data in our customer class that will never be populated before the values have been matched in our system (step 2). For this reason, I would like to have the values not even be available to be accessed when the customer is in this state, and I would like to have to avoid some repeated logic everywhere like: if (customer.IsMatched) DisplayTextOnWeb(customer.SomeMatchedValue); My first thought for this was to add a couple interfaces on top of Customer that would only expose the properties and behaviors of the current state, and then only deal with those interfaces. The problem with this approach is that there seems to be no good way to move from an ICustomerWithNoMatchedValues to an ICustomerWithMatchedValues without doing direct casts, etc... (or at least I can't find one). I can't be the first to have come across this, how do you normally approach this? As a last caveat, I would like for this solution to play nice with FluentNHibernate :) Thanks in advance...

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• GRID is not properly rendered in ExtJS 4 by using Store

  - by user548543

  Here is the Src code for HTML file <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4 /strict.dtd"> <html> <head> <title>MVC Architecture</title> <link rel="stylesheet" type="text/css" href="/bh/extjs/resources/css/ext-all.css" /> <script type="text/javascript" src="extjs/ext-debug.js"></script> <script type="text/javascript" src="Main.js"></script> </head> <body> </body> </html> File path: /bh/Main.js [Main File] Ext.require('Ext.container.Viewport'); Ext.application({ name: 'App', appFolder: 'app', controllers: ['UserController'], launch: function() { Ext.create('Ext.container.Viewport', { layout: 'border', items: [ { xtype: 'userList' } ] }); } }); File path: /app/controller/UserController.js [Controller] Ext.define('App.controller.UserController',{ extend: 'Ext.app.Controller', stores: ['UserStore'], models:['UserModel'], views:['user.UserList'], init: function() { this.getUserStoreStore().load(); } }); File path: /app/store/UserStore.js Ext.define('App.store.UserStore', { extend: 'Ext.data.Store', model: 'App.model.UserModel', proxy: { type: 'ajax', url: 'app/data/contact.json' } }); File path: /app/model/UserModel.js [Model] Ext.define('App.model.UserModel',{ extends:'Ext.data.Model', fields:[ {name: 'name', type: 'string'}, {name: 'age', type: 'string'}, {name: 'phone', type: 'string'}, {name: 'email', type: 'string'} ] }); File path: /app/view/UserList.js [View] Ext.define('App.view.user.UserList' ,{ extend: 'Ext.grid.Panel', alias:'widget.userList', title:'Contacts', region:'center', resizable:true, initComponent: function() { this.store = 'UserStore'; this.columns = [ {text: 'Name',flex:1,sortable: true,dataIndex: 'name'}, {text: 'Age',flex:1,sortable: true,dataIndex: 'age'}, {text: 'Phone',flex:1,sortable: true,dataIndex: 'phone'}, {text: 'Email',flex:1,sortable: true,dataIndex: 'email'} ]; this.callParent(arguments); } }); In fire bug it shows the JSON response as follows: [{ "name": "Aswini", "age": "32", "phone": "555-555-5555", "email": "[email protected]" }] Why the Data has not been displayed although I have a valid json response. Please help!!!

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• How can I add the column data type after adding the column headers to my datatable?

  - by Kevin

  Using the code below (from a console app I've cobbled together), I add seven columns to my datatable. Once this is done, how can I set the data type for each column? For instance, column 1 of the datatable will have the header "ItemNum" and I want to set it to be an Int. I've looked at some examples on thet 'net, but most all of them show creating the column header and column data type at once, like this: loadDT.Columns.Add("ItemNum", typeof(Int)); At this point in my program, the column already has a name. I just want to do something like this (not actual code): loadDT.Column[1].ChangeType(typeof(int)); Here's my code so far (that gives the columns their name): // get column headings for datatable by reading first line of csv file. StreamReader sr = new StreamReader(@"c:\load_forecast.csv"); headers = sr.ReadLine().Split(','); foreach (string header in headers) { loadDT.Columns.Add(header); } Obviously, I'm pretty new at this, but trying very hard to learn. Can someone point me in the right direction? Thanks!

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• MS Access 2003 - Is there a way to programmatically define the data for a chart?

  - by Justin

  So I have some VBA for taking charts built with the Form's Chart Wizard, and automatically inserting it into PowerPoint Presentation slides. I use those chart-forms as sub forms within a larger forms that has parameters the user can select to determine what is on the chart. The idea is that the user can determine the parameter, build the chart to his/her liking, and click a button and have it in a ppt slide with the company's background template, blah blah blah..... So it works, though it is very bulky in terms of the amount of objects I have to use to accomplish this. I use expressions such as the following: like forms!frmMain.Month&* to get the input values into the saved queries, which was fine when i first started, but it went over so well and they want so many options, that it is driving the number of saved queries/objects up. I need several saved forms with charts because of the number of different types of charts I need to have this be able to handle. SO FINALLY TO MY QUESTION: I would much rather do all this on the fly with some VBA. I know how to insert list boxes, and text boxes on a form, and I know how to use SQL in VBA to get the values I want from tables/queries using VBA, I just don't know if there is some vba I can use to set the data values of the charts from a resulting recordset: DIM rs AS DAO.Rescordset DIM db AS DAO.Database DIM sql AS String sql = "SELECT TOP 5 Count(tblMain.TransactionID) AS Total, tblMain.Location FROM tblMain WHERE (((tblMain.Month) = """ & me.txtMonth & """ )) ORDER BY Count (tblMain.TransactionID) DESC;" set db = currentDB set rs = db.OpenRecordSet(sql) rs.movefirst some kind of cool code in here to make this recordset the data of chart in frmChart ("Chart01") thanks for your help. apologies for the length of the explanation.

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• How to create a list of data clickable? asp.net

  - by Roger Filipe

  Hello, I am learning asp.net but I'm finding some problems. My doubt is how to make a list of titles of news contained in a database. And in this list, each of the titles when clicked is redirected to a page where you will be able to view the news in full (Title, Body, Author ..). What I got: - A database containing a table with the news, every news is associated with an identification code (ex: "ID"). - A page where you will make the listing. (Ex: site / listofnews.aspx) - I have a page that uses the method "querystring" to know what is the primarykey the news. (Ex: site/shownews.aspx?ID=12345, where "12345" is the primarykey of the news. Once it knows what is the primarykey of the news in the database, it loads each of the fields of the page (news.aspx) with the news, this part is working ok. - The data is retrieve using the Linq, so I receive a List of "News", the class "News" as ID, Title, Body, Author.. My doubt is how to make the listing clickable. In php I used this method (make a list of html links, in each link the href field is changed so that the tag "id" coincides with the news): //database used is oracle, $stmt is the query, you don´t need to understand how it works. oci_define_by_name($stmt, "ID", $id); oci_define_by_name($stmt, "TITLE", $title); if (!oci_execute($stmt, OCI_DEFAULT)) { $err = oci_error($stmt); trigger_error('Query failed: ' . $err['message'], E_USER_ERROR); } echo '<br />'; while (oci_fetch($stmt)) {<------While there is data from the database , create links $link = '<a href="site/shownews.php?ID='.$id.'" >'.$title.'</a>';<----the shownews.php?ID= $id, creates the link according with the ID echo $link<---Prints the link echo '<br />'; } How do i make the same with asp.net?

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• What is the return type for a anonymous linq query select? What is the best way to send this data ba

  - by punkouter

  This is a basic question. I have the basic SL4/RIA project set up and I want to create a new method in the domain service and return some data from it. I am unsure the proper easiest way to do this.. Should I wrap it up in a ToList()? I am unclear how to handle this anonymous type that was create.. what is the easiest way to return this data? public IQueryable<ApplicationLog> GetApplicationLogsGrouped() { var x = from c in ObjectContext.ApplicationLogs let dt = c.LogDate group c by new { y = dt.Value.Year, m = dt.Value.Month, d = dt.Value.Day } into mygroup select new { aaa = mygroup.Key, ProductCount = mygroup.Count() }; return x; // return this.ObjectContext.ApplicationLogs.Where(r => r.ApplicationID < 50); } Cannot implicitly convert type 'System.Linq.IQueryable<AnonymousType#1>' to 'System.Linq.IQueryable<CapRep4.Web.ApplicationLog>'. An explicit conversion exists (are you missing a cast?) 58 20 CapRep4.Web

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• What algorithm should i follow to retrieve data in the prescribed format?

  - by Prateek

  I have to retrieve data from a database in which tables are consisting of fields like "ttc, rm, atc and lta" namely. Actually these values are stored on daily basis with a 15 min interval like From_time to_time ttc rm atc lta 00:00 00:15 45 10 35 25, 00:15 00:30 35 10 25 25 and so on .. These values are stored for every day of every month and i want it to be previewed in the prescribed format then what algorithm should i follow. I am confused about how to do comparisons for a format like below mentioned. The format is at this link https://drive.google.com/a/itbhu.ac.in/file/d/0B_J0Ljq64i4Za2J1V0lvbDZ4eGc/edit?usp=sharing To be specific once again, my question is, I have to prepare a report from the retrieved data which is being stored in the databases as explained above. But the report which is going to be prepared will be of entire month. So, to say the least, there may be cases that for two particular days the value of "ttc" would be same for some time so i want it to be listed together (as shown in format). And the confusing part is any of the values "ttc", "rm", "atc", "lta" can be same for any particular interval. So what algorithm should i follow for such comparisons. And if still any query with question, u can ask your doubt. Thanks

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• View Models (ViewData), UserControls/Partials and Global variables - best practice?

  - by elado

  Hi I'm trying to figure out a good way to have 'global' members (such as CurrentUser, Theme etc.) in all of my partials as well as in my views. I don't want to have a logic class that can return this data (like BL.CurrentUser) I do think it needs to be a part of the Model in my views So I tried inheriting from BaseViewData with these members. In my controllers, in this way or another (a filter or base method in my BaseController), I create an instance of the inheriting class and pass it as a view data. Everything's perfect till this point, cause then I have my view data available on the main View with the base members. But what about partials? If I have a simple partial that needs to display a blog post then it looks like this: <%@ Control Language="C#" AutoEventWireup="true" Inherits="ViewUserControl<Post>" %> and simple code to render this partial in my view (that its model.Posts is IEnumerable<Post>): <%foreach (Post p in this.Model.Posts) {%> <%Html.RenderPartial("Post",p); %> <%}%> Since the partial's Model isn't BaseViewData, I don't have access to those properties. Hence, I tried to make a class named PostViewData which inherits from BaseViewData, but then my containing views will have a code to actually create the PostViewData in them in order to pass it to the partial: <%Html.RenderPartial("Post",new PostViewData { Post=p,CurrentUser=Model.CurrentUser,... }); %> Or I could use a copy constructor <%Html.RenderPartial("Post",new PostViewData(Model) { Post=p }); %> I just wonder if there's any other way to implement this before I move on. Any suggestions? Thanks!

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• Is there a better (i.e vectorised) way to put part of a column name into a row of a data frame in R

  - by PaulHurleyuk

  I have a data frame in R that has come about from running some stats on the result fo a melt/cast operation. I want to add a row into this dataframe containing a Nominal value. That Nominal Value is present in the names for each column df<-as.data.frame(cbind(x=c(1,2,3,4,5),`Var A_100`=c(5,4,3,2,1),`Var B_5`=c(9,8,7,6,5))) > df x Var A_100 Var B_5 1 1 5 9 2 2 4 8 3 3 3 7 4 4 2 6 5 5 1 5 So, I want to create a new row, that contains '100' in the column Var A_100 and '5' in Var B_5. Currently this is what I'm doing but I'm sure there must be a better, vectorised way to do this. temp_nom<-NULL for (l in 1:length(names(df))){ temp_nom[l]<-strsplit(names(df),"_")[[l]][2] } temp_nom [1] NA "100" "5" df[6,]<-temp_nom > df x Var A_100 Var B_5 1 1 5 9 2 2 4 8 3 3 3 7 4 4 2 6 5 5 1 5 6 <NA> 100 5 rm(temp_nom) Typically I'd have 16-24 columns. Any ideas ?

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• What is the performance penalty of XML data type in SQL Server when compared to NVARCHAR(MAX)?

  - by Piotr Owsiak

  I have a DB that is going to keep log entries. One of the columns in the log table contains serialized (to XML) objects and a guy on my team proposed to go with XML data type rather than NVARCHAR(MAX). This table will have logs kept "forever" (archiving some very old entries may be considered in the future). I'm a little worried about the CPU overhead, but I'm even more worried that DB can grow faster (FoxyBOA from the referenced question got 70% bigger DB when using XML). I have read this question http://stackoverflow.com/questions/514827/microsoft-sql-server-2005-2008-xml-vs-text-varchar-data-type and it gave me some ideas but I am particulairly interrested in clarification on whether the DB size increases or decreases. Can you please share your insight/experiences in that matter. BTW. I don't currently have any need to depend on XML features within SQL Server (there's nearly zero advantage to me in the specific case). Ocasionally log entries will be extracted, but I prefer to handle the XML using .NET (either by writing a small client or using a function defined in a .NET assembly).

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• How should backbone.js handle a GET request that returns no results?

  - by Nyxynyx

  I have a number of text input elements that when its values are changed, will trigger a fetch on listingListView's collection listingCollection, which then updates listingListView with the new data via the function listingListView.refreshList as shown below. I am using PHP/Codeigniter to expose a RESTful API. Problem: Everything works fine if there are results retrieved from the fetch(). However, when the filters results in no result being returned, how should the server side and the client side handle it? Currently Chrome's javascript console displays a 404 error and in the Network tab, the XHR request is highlighted in red. All I want to do in the event of zero results returned, is to blank the listingListView and show a message like (No results returned) and not throw any errors in the javascript console. Thanks! PHP Code function listings_get() { // Get filters $price_min = $this->get('price_min'); $this->load->model('app_model'); $results = $this->app_model->get_listings($price_min); if($results) $this->response($results); else $this->response(NULL); } JS Code window.ListingListView = Backbone.View.extend({ tagName: 'table', initialize: function() { this.model.bind('reset', this.refreshList, this); this.model.bind('add', function(listing) { $(this.el).append(new ListingListItemView({ model: listing }).render().el); }, this); }, render: function() { _.each(this.model.models, function(listing) { $(this.el).append(new ListingListItemView({ model: listing }).render().el); }, this); return this; }, close: function() { $(this.el).unbind(); $(this.el).empty(); }, refreshList: function() { $(this.el).empty(); this.render(); } });

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• What is jasper report's algorithm for using a data source?

  - by spderosso

  Hi, I have created my custom data source by implementing the interface JRDataSource. This interface looks like this: public interface JRDataSource { /** * Tries to position the cursor on the next element in the data source. * @return true if there is a next record, false otherwise * @throws JRException if any error occurs while trying to move to the next element */ public boolean next() throws JRException; /** * Gets the field value for the current position. * @return an object containing the field value. The object type must be the field object type. */ public Object getFieldValue(JRField jrField) throws JRException; } My question is the following: In what way does jasper report call this functions for obtaining the fields in the .jrxml. E.g: if( next() )){ call getFieldValue for every field present in the page header while( next() ){ call getFieldValue for every field present in detail part } call getFieldValue for every field present the footer } The previous is just an example, experimentally in fact I found out that it is actually not like that. So my question arised. Thanks!

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• Action Mailer: How do I render dynamic data in an email body that is stored in the database?

  - by Brandon Toone

  I have Action Mailer setup to render an email using the body attribute of my Email model (in the database). I want to be able to use erb in the body but I can't figure out how to get it to render in the sent email message. I'm able to get the body as a string with this code # models/user_mailer.rb def custom_email(user, email_id) email = Email.find(email_id) recipients user.email from "Mail It Example <[email protected]>" subject "Hello From Mail It" sent_on Time.now # pulls the email body and passes a string to the template views/user_mailer/customer_email.text.html.erb body :msg => email.body end I came across this article http://rails-nutshell.labs.oreilly.com/ch05.html which says I can use render but I'm only able to get render :text to work and not render :inline # models/user_mailer.rb def custom_email(user, email_id) email = Email.find(email_id) recipients user.email from "Mail It Example <[email protected]>" subject "Hello From Mail It" sent_on Time.now # body :msg => email.body body :msg => (render :text => "Thanks for your order") # renders text and passes as a variable to the template # body :msg => (render :inline => "We shipped <%= Time.now %>") # throws a NoMethodError end

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• asp.net mvc ajax helper/post additional data w/o jquery.

  - by Jopache

  I would like to use the ajax helper to create ajax requests that send additional, dynamic data with the post (for example, get the last element with class = blogCommentDateTime and send the value of that last one to the controller which will return only blog comments after it). I have successfully done so with the help of jQuery Form plugin like so: $(document).ready(function () { $("#addCommentForm").submit(function () { var lastCommentDate = $(".CommentDateHidden:last").val(); var lastCommentData = { lastCommentDateTicks: lastCommentDate }; var formSubmitParams = { data: lastCommentData, success: AddCommentResponseHandler } $("#addCommentForm").ajaxSubmit(formSubmitParams); return false; }); This form was created with html.beginform() method. I am wondering if there is an easy way to do this using the ajax.beginform() helper? When I try to use the same code but replace html.beginform() with ajax.beginform(), when i try to submit the form, I am issuing 2 posts (which is understandable, one being taken care of by the helper, the other one by me with the JS above. I can't create 2 requests, so this option is out) I tried getting rid of the return false and changing ajaxSubmit() to ajaxForm() so that it would only "prepare" the form, and this leads in only one post, but it does not include the extra parameter that I defined, so this is worthless as well. I then tried keeping the ajaxForm() but calling that whenever the submit button on the form gets clicked rather than when the form gets submitted (I guess this is almost the same thing) and that results in 2 posts also. The biggest reason I am asking this question is that I have run in to some issues with the javascript above and using mvc validation provided by the mvc framework (which i will set up another question for) and would like to know this so I can dive further in to my validation issue.

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• django: control json serialization

  - by abolotnov

  Is there a way to control json serialization in django? Simple code below will return serialized object in json: co = Collection.objects.all() c = serializers.serialize('json',co) The json will look similar to this: [ { "pk": 1, "model": "picviewer.collection", "fields": { "urlName": "architecture", "name": "\u0413\u043e\u0440\u043e\u0434 \u0438 \u0430\u0440\u0445\u0438\u0442\u0435\u043a\u0442\u0443\u0440\u0430", "sortOrder": 0 } }, { "pk": 2, "model": "picviewer.collection", "fields": { "urlName": "nature", "name": "\u041f\u0440\u0438\u0440\u043e\u0434\u0430", "sortOrder": 1 } }, { "pk": 3, "model": "picviewer.collection", "fields": { "urlName": "objects", "name": "\u041e\u0431\u044a\u0435\u043a\u0442\u044b \u0438 \u043d\u0430\u0442\u044e\u0440\u043c\u043e\u0440\u0442", "sortOrder": 2 } } ] You can see it's serializing it in a way that you are able to re-create the whole model, shall you want to do this at some point - fair enough, but not very handy for simple JS ajax in my case: I want bring the traffic to minimum and make the whole thing little clearer. What I did is I created a view that passes the object to a .json template and the template will do something like this to generate "nicer" json output: [ {% if collections %} {% for c in collections %} {"id": {{c.id}},"sortOrder": {{c.sortOrder}},"name": "{{c.name}}","urlName": "{{c.urlName}}"}{% if not forloop.last %},{% endif %} {% endfor %} {% endif %} ] This does work and the output is much (?) nicer: [ { "id": 1, "sortOrder": 0, "name": "????? ? ???????????", "urlName": "architecture" }, { "id": 2, "sortOrder": 1, "name": "???????", "urlName": "nature" }, { "id": 3, "sortOrder": 2, "name": "??????? ? ?????????", "urlName": "objects" } ] However, I'm bothered by the fast that my solution uses templates (an extra step in processing and possible performance impact) and it will take manual work to maintain shall I update the model, for example. I'm thinking json generating should be part of the model (correct me if I'm wrong) and done with either native python-json and django implementation but can't figure how to make it strip the bits that I don't want. One more thing - even when I restrict it to a set of fields to serialize, it will keep the id always outside the element container and instead present it as "pk" outside of it.

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• Managing inverse relationships without CoreData

  - by Nathaniel Martin

  This is a question for Objective-J/Cappuccino, but I added the cocoa tag since the frameworks are so similar. One of the downsides of Cappuccino is that CoreData hasn't been ported over yet, so you have to make all your model objects manually. In CoreData, your inverse relationships get managed automatically for you... if you add an object to a to-many relationship in another object, you can traverse the graph in both directions. Without CoreData, is there any clean way to setup those inverse relationships automatically? For a more concrete example, let's take the typical Department and Employees example. To use rails terminology, a Department object has-many Employees, and an Employee belongs-to a Department. So our Department model has an NSMutableSet (or CPMutableSet ) "employees" that contains a set of Employees, and our Employee model has a variable "department" that points back to the Department model that owns it. Is there an easy way to make it so that, when I add a new Employee model into the set, the inverse relationship (employee.department) automatically gets set? Or the reverse: If I set the department model of an employee, then it automatically gets added to that department's employee set? Right know I'm making an object, "ValidatedModel" that all my models subclass, which adds a few methods that setup the inverse relationships, using KVO. But I'm afraid that I'm doing a lot of pointless work, and that there's already an easier way to do this. Can someone put my concerns to rest?

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• Ruby on Rails Associations

  - by Eef

  Hey all, I am starting to create my sites in Ruby on Rails these days instead of PHP. I have picked up the language easily but still not 100% confident with associations :) I have this situation: User Model has_and_belongs_to_many :roles Roles Model has_and_belongs_to_many :users Journal Model has_and_belongs_to_many :roles So I have a roles_users table and a journals_roles table I can access the user roles like so: user = User.find(1) User.roles This gives me the roles assigned to the user, I can then access the journal model like so: journals = user.roles.first.journals This gets me the journals associated with the user based on the roles. I want to be able to access the journals like so user.journals In my user model I have tried this: def journals self.roles.collect { |role| role.journals }.flatten end This gets me the journals in a flatten array but unfortunately I am unable to access anything associated with journals in this case, e.g in the journals model it has: has_many :items When I try to access user.journals.items it does not work as it is a flatten array which I am trying to access the has_many association. Is it possible to get the user.journals another way other than the way I have shown above with the collect method? Hope you guys understand what I mean, if not let me know and ill try to explain it better. Cheers Eef

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• Sql server query using function and view is slower

  - by Lieven Cardoen

  I have a table with a xml column named Data: CREATE TABLE [dbo].[Users]( [UserId] [int] IDENTITY(1,1) NOT NULL, [FirstName] [nvarchar](max) NOT NULL, [LastName] [nvarchar](max) NOT NULL, [Email] [nvarchar](250) NOT NULL, [Password] [nvarchar](max) NULL, [UserName] [nvarchar](250) NOT NULL, [LanguageId] [int] NOT NULL, [Data] [xml] NULL, [IsDeleted] [bit] NOT NULL,... In the Data column there's this xml <data> <RRN>...</RRN> <DateOfBirth>...</DateOfBirth> <Gender>...</Gender> </data> Now, executing this query: SELECT UserId FROM Users WHERE data.value('(/data/RRN)[1]', 'nvarchar(max)') = @RRN after clearing the cache takes (if I execute it a couple of times after each other) 910, 739, 630, 635, ... ms. Now, a db specialist told me that adding a function, a view and changing the query would make it much more faster to search a user with a given RRN. But, instead, these are the results when I execute with the changes from the db specialist: 2584, 2342, 2322, 2383, ... This is the added function: CREATE FUNCTION dbo.fn_Users_RRN(@data xml) RETURNS varchar(100) WITH SCHEMABINDING AS BEGIN RETURN @data.value('(/data/RRN)[1]', 'varchar(max)'); END; The added view: CREATE VIEW vwi_Users WITH SCHEMABINDING AS SELECT UserId, dbo.fn_Users_RRN(Data) AS RRN from dbo.Users Indexes: CREATE UNIQUE CLUSTERED INDEX cx_vwi_Users ON vwi_Users(UserId) CREATE NONCLUSTERED INDEX cx_vwi_Users__RRN ON vwi_Users(RRN) And then the changed query: SELECT UserId FROM Users WHERE dbo.fn_Users_RRN(Data) = '59021626919-61861855-S_FA1E11' Why is the solution with a function and a view going slower?

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• How to handle not-enough-isolatedstorage issue deep in data loader?

  - by Edward Tanguay

  I have a silverlight application which loads data from many external data sources into IsolatedStorage, and while loading any of these sources if it does not have enough IsolatedStorage, it ends up in a catch statement. At that point in that catch statement I would like to ask the user to click a button to approve silverlight to increase the IsolatedStorage capacity. The problem is, although I have a "SwitchPage()" method with which I display a page, if I access it at this point it is too deep in the loading process and the application always goes into an endless loop, hangs and crashes. I need a way to branch out of the application completely somehow to an independent UserControl which has a button and code behind which does the increase logic. What is a solution for an application to be able to branch out of a loading process catch statement like this, display a user control which has a button to ask the user to increase the IsolatedStorage? public static void SaveBitmapImageToIsolatedStorageFile(OpenReadCompletedEventArgs e, string fileName) { try { using (IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication()) { using (IsolatedStorageFileStream isfs = new IsolatedStorageFileStream(fileName, FileMode.Create, isf)) { Int64 imgLen = (Int64)e.Result.Length; byte[] b = new byte[imgLen]; e.Result.Read(b, 0, b.Length); isfs.Write(b, 0, b.Length); isfs.Flush(); isfs.Close(); isf.Dispose(); } } } catch (IsolatedStorageException) { //handle: present user with button to increase isolated storage } catch (TargetInvocationException) { //handle: not saved } }

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• Hashing the state of a complex object in .NET

  - by Jan

  Some background information: I am working on a C#/WPF application, which basically is about creating, editing, saving and loading some data model. The data model contains of a hierarchy of various objects. There is a "root" object of class A, which has a list of objects of class B, which each has a list of objects of class C, etc. Around 30 classes involved in total. Now my problem is that I want to prompt the user with the usual "you have unsaved changes, save?" dialog, if he tries to exit the program. But how do I know if the data in current loaded model is actually changed? There is of course ways to solve this, like e.g. reloading the model from file and compare against the one in memory value by value or make every UI control set a flag indicating the model has been changed. Now instead, I want to create a hash value based on the model state on load and generate a new value when the user tries to exit, and compare those two. Now the question: So inspired of that, I was wondering if there exist some way to generate a hash value from the (value)state of some arbitrary complex object? Preferably in a generic way, e.g. no need to apply attributes to each involved class/field. One idea could be to use some of .NET's serialization functionality (assuming it will work out-of-the-box in this case) and apply a hash function to the content of the resulting file. However, I guess there exist some more suitable approach. Thanks in advance.

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• Java equivalent of the VB Request.InputStream

  - by Android Addict

  I have a web service that I am re-writing from VB to a Java servlet. In the web service, I want to extract the body entity set on the client-side as such: StringEntity stringEntity = new StringEntity(xml, HTTP.UTF_8); stringEntity.setContentType("application/xml"); httppost.setEntity(stringEntity); In the VB web service, I get this data by using: Dim objReader As System.IO.StreamReader objReader = New System.IO.StreamReader(Request.InputStream) Dim strXML As String = objReader.ReadToEnd and this works great. But I am looking for the equivalent in Java. I have tried this: ServletInputStream dataStream = req.getInputStream(); byte[] data = new byte[dataStream.toString().length()]; dataStream.read(data); but all it gets me is an unintelligible string: data = [B@68514fec Please advise. Edit Per the answers, I have tried: ServletInputStream dataStream = req.getInputStream(); ByteArrayOutputStream buffer = new ByteArrayOutputStream(); int r; byte[] data = new byte[1024*1024]; while ((r = dataStream.read(data, 0, data.length)) != -1) { buffer.write(data, 0, r); } buffer.flush(); byte[] data2 = buffer.toByteArray(); System.out.println("DATA = "+Arrays.toString(data2)); whichs yields: DATA = [] and when I try: System.out.println("DATA = "+data2.toString()); I get: DATA = [B@15282c7f So what am I doing wrong? As stated earlier, the same call to my VB service gives me the xml that I pass in.

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• JSP: Refresh ComboBox options

  - by framara

  Hi, There's a class 'Car' with brand and model as properties. I have a list of items of this class List<Car> myCars. I need to represent in a JSP website 2 ComboBox, one for brand and another for model, that when you select the brand, in the model list only appear the ones from that brand. I don't know how to do this in a dynamic way. Any suggestion where to start? Thanks Update Ok, what I do now is send in the request a list with all the brand names, and a list of the items. The JSP code is like: <select name="manufacturer" id="id_manufacturer" onchange="return getManufacturer();"> <option value=""></option> <c:forEach items="${manufacturers}" var="man"> <option value="${man}" >${man}</option> </c:forEach> </select> <select name="model" id="id_model"> <c:forEach items="${mycars}" var="car"> <c:if test="${car.manufacturer eq man_selected}"> <option value="${car.id}">${car.model}</option> </c:if> </c:forEach> </select> <script> function getManufacturer() { man_selected = document.getElementById('id_manufacturer').value; } </script> How do I do to refresh the 'model' select options according to the selected 'man_selected' ?

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• How to display objects with dynamic fields in wpf data grid?

  - by Oliver Hanappi

  Hi! I want to display and edit some objects in a WPF data grid and I'm looking for a good way to do so. All objects I want to display have the same fields, but every execution the fields of my objects can differ. Here is a piece of the interface to illustrate what I mean: public interface IMyObject { IEnumerable<string> GetFieldNames(); IEnumerable<Type> GetFieldTypes(); object GetField(string name); void SetField(string name, object value); } How can I generate a data grid which displays this kind of objects? I thought of XAML generation to define the columns, but I'm still facing the problem of accessing the fields. I think I could realize this with value converters, another option would be to dynamically create a type which exposes the dynamic fields with properties. Are there any other ways and which should I favor? I'm keen on hearing your opinions. Best Regards, Oliver Hanappi

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