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  • C# generics with MVVM, pulling the T out of <T>

    - by bufferz
    My Model is a generic class that contains a (for example) Value property which can be int, float, string, bool, etc. So naturally this class is represented something like Model<T>. For the sake of collections Model<T> implements the interface IModel, although IModel is itself empty of any content. My ViewModel contains and instance of Model<T> and it is passed in through ViewModel's constructor. I still want to know what T is in ViewModel, so when I expose Model to the View I know the datatype of Model's buried Value property. The class for ViewModel ends up looking like the following: class ViewModel<T> { private Model<T> _model; public ViewModel(Model<T> model) { ....blah.... } public T ModelsValue {get; set; } } This works fine, but is limited. So now I need to expose a collection of IModels with varying Ts to my View, so I'm trying to set up an ObservableCollection of new ViewModel<T>s to a changing list of IModels. The problem is, I can't figure out how to get T from Model<T> from IModel to construct ViewModel<T>(Model<T>) at runtime. In the VS2010 debugger I can mouseover any IModel object and see its full Model<int> for example at runtime so I know the data is in there. Any ideas?

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  • IIS7.5 and MVC 2 : Implementing HTTP(S) security

    - by Program.X
    This is my first ASP.NET MVC application, and my first on an IIS 7.x installation whereby I have to do anything over and above the standard. I need to enforce Windows authentication on the /Index and /feeds/xxx.svc pages/services. In ASP.NET Web Forms, I would apply the Windows permissions on the files and remove Anonymous authentication in IIS 6. This needs to work over HTTP/S, but don't worry about that, that's in hand. What happens in MVC/IIS 7? I have tried modifying the permissions on the /Index.aspx view, which seems to block access. It asks me for a username/password, but does not grant access when I enter a valid username/password. Pressing Escape gives me an exception "*Access to the path 'E:\dev\xxx\xxx.ConsultantRegistration.Web.Admin\Views\ConsultantRegistration\index.aspx' is denied. *", which does get sent as a 401. So although the username/password does exist on the Index.aspx view, I can't use those credentials to access said view. I have in my web.config: What am I missing?

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  • Repository Pattern Standardization of methods

    - by Nix
    All I am trying to find out the correct definition of the repository pattern. My original understanding was this (extremely dubmed down) Separate your Business Objects from your Data Objects Standardize access methods in data access layer. I have really seen 2 different implementations. Implementation 1 : public Interface IRepository<T>{ List<T> GetAll(); void Create(T p); void Update(T p); } public interface IProductRepository: IRepository<Product> { //Extension methods if needed List<Product> GetProductsByCustomerID(); } Implementation 2 : public interface IProductRepository { List<Product> GetAllProducts(); void CreateProduct(Product p); void UpdateProduct(Product p); List<Product> GetProductsByCustomerID(); } Notice the first is generic Get/Update/GetAll, etc, the second is more of what I would define "DAO" like. Both share an extraction from your data entities. Which I like, but i can do the same with a simple DAO. However the second piece standardize access operations I see value in, if you implement this enterprise wide people would easily know the set of access methods for your repository. Am I wrong to assume that the standardization of access to data is an integral piece of this pattern ? Rhino has a good article on implementation 1, and of course MS has a vague definition and an example of implementation 2 is here.

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  • java.lang.IllegalStateException: The content of the adapter has changed but ListView.... inspite of calling notifydatasetchanged()

    - by Mistaken
    What are the best practices to be followed to update the contents of a listactivty by a background thread (Async Task) ? 1) Am calling the notifyDataSetChanged() to update the adapter as soon as i manipulate the contents of the adapter but still my app force closes while the user scrolls or click on the list. Any pointers to prevent this would be very helpfull. Logcat: java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. 2) Where exaclty should i update contents of the listactivity ? inside the doInBackground() or onProgressUpdate()? 3) Am experiencing regular crashes when the user clicks the list item. So will disabling click events on the listactivty during the background operation solve the problem ? If so am not sure how to remove or set item click listeners dynamically to the listactivity. Please instruct me on the too. 4) I dont think blocking all ui interactions during the background async task execution is the only way to solve the problem. I know there is a simple way of doing this but need some help. Thanks in advance. This is my onCreate... protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.fa); tvStatus=(TextView) findViewById(R.id.tvStatus); adapter = new SimpleAdapter( this, mostPopularList, R.layout.list_item, new String[] {"title","author","views","date"}, new int[] {R.id.textView1,R.id.textView2,R.id.textView4,R.id.textView3}); //populateList(); setListAdapter(adapter); } My async task... private class LongOperation extends AsyncTask<String, Void, String> { @Override protected String doInBackground(String... params) { // code for adding new listactivty items } @Override protected void onPostExecute(String networkStatus) { adapter.notifyDataSetChanged(); } @Override protected void onPreExecute() { } @Override protected void onProgressUpdate(Void... values) { } }

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  • Jquery passing an HTML element into a function

    - by christian
    I have an HTML form where I am going to copy values from a series of input fields to some spans/headings as the user populates the input fields. I am able to get this working using the following code: $('#source').keyup(function(){ if($("#source").val().length == 0){ $("#destinationTitle").text('Sample Title'); }else{ $("#destinationTitle").text($("#source").val()); } }); In the above scenario the html is something like: Sample Title Basically, as the users fills out the source box, the text of the is changed to the value of the source input. If nothing is input in, or the user deletes the values typed into the box some default text is placed in the instead. Pretty straightforward. However, since I need to make this work for many different fields, it makes sense to turn this into a generic function and then bind that function to each 's onkeyup() event. But I am having some trouble with this. My implementation: function doStuff(source,target,defaultValue) { if($(source).val().length == 0){ $(target).text(defaultValue); }else{ $(target).text($(source).val()); } } which is called as follows: $('#source').keyup(function() { doStuff(this, '"#destinationTitle"', 'SampleTitle'); }); What I can't figure out is how to pass the second parameter, the name of the destination html element into the function. I have no problem passing in the element I'm binding to via "this", but can't figure out the destination element syntax. Any help would be appreciated - many thanks!

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  • PHP: Opening/closing tags & performance?

    - by Tom
    Hi, This may be a silly question, but as someone relatively new to PHP, I'm wondering if there are any performance-related issues to frequently opening and closing PHP tags in HTML template code, and if so, what might be best practices in terms of working with php tags? My question is not about the importance/correctness of closing tags, or about which type of code is more readable than another, but rather about how the document gets parsed/executed and what impact it might have on performance. To illustrate, consider the following two extremes: Mixing PHP and HTML tags: <?php echo '<tr> <td>'.$variable1.'</td> <td>'.$variable2.'</td> <td>'.$variable3.'</td> <td>'.$variable4.'</td> <td>'.$variable5.'</td> </tr>' ?> // PHP tag opened once Separating PHP and HTML tags: <tr> <td><?php echo $variable1 ?></td> <td><?php echo $variable2 ?></td> <td><?php echo $variable3 ?></td> <td><?php echo $variable4 ?></td> <td><?php echo $variable5 ?></td> </tr> // PHP tag opened five times Would be interested in hearing some views on this, even if it's just to hear that it makes no difference. Thanks.

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  • How is covariance cooler than polymorphism...and not redundant?

    - by P.Brian.Mackey
    .NET 4 introduces covariance. I guess it is useful. After all, MS went through all the trouble of adding it to the C# language. But, why is Covariance more useful than good old polymorphism? I wrote this example to understand why I should implement Covariance, but I still don't get it. Please enlighten me. using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Sample { class Demo { public delegate void ContraAction<in T>(T a); public interface IContainer<out T> { T GetItem(); void Do(ContraAction<T> action); } public class Container<T> : IContainer<T> { private T item; public Container(T item) { this.item = item; } public T GetItem() { return item; } public void Do(ContraAction<T> action) { action(item); } } public class Shape { public void Draw() { Console.WriteLine("Shape Drawn"); } } public class Circle:Shape { public void DrawCircle() { Console.WriteLine("Circle Drawn"); } } public static void Main() { Circle circle = new Circle(); IContainer<Shape> container = new Container<Circle>(circle); container.Do(s => s.Draw());//calls shape //Old school polymorphism...how is this not the same thing? Shape shape = new Circle(); shape.Draw(); } } }

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  • jquery window.unload triggers post after unload

    - by index
    I am trying to do a post to server before unloading a page and I followed this and it's working fine. My problem is the $.post on window.unload is triggered after it has unloaded. I tried it with a signout link and checking on my logs, I get the following: Started GET "/signout" for 127.0.0.1 at 2012-11-22 00:15:08 +0800 Processing by SessionsController#destroy as HTML Redirected to http://localhost:3000/ Completed 302 Found in 1ms Started GET "/" for 127.0.0.1 at 2012-11-22 00:15:08 +0800 Processing by HomeController#index as HTML Rendered home/index.html.erb within layouts/application (0.4ms) Rendered layouts/_messages.html.erb (0.1ms) Completed 200 OK in 13ms (Views: 12.9ms) Started POST "/unloading" for 127.0.0.1 at 2012-11-22 00:15:08 +0800 Processing by HomeController#unloading as */* Parameters: {"p1"=>"1"} WARNING: Can't verify CSRF token authenticity Completed 500 Internal Server Error in 0ms NoMethodError (undefined method `id' for nil:NilClass): app/controllers/home_controller.rb:43:in `unloading' First part is the signout and then user gets redirected to root then it runs the post ('/unloading'). Is there a way to make the '/unloading' execute first then execute whatever the unload action was? I have this as my jquery post $(window).unload -> $.ajax { async: false, beforeSend: (xhr) -> xhr.setRequestHeader('X-CSRF-Token', $('meta[name="csrf-token"]').attr('content')) , url: '/unloading' , type: 'Post' , data: { p1: '1' } }

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  • Execute JavaScript from within a C# assembly

    - by ScottKoon
    I'd like to execute JavaScript code from within a C# assembly and have the results of the JavaScript code returned to the calling C# code. It's easier to define things that I'm not trying to do: I'm not trying to call a JavaScript function on a web page from my code behind. I'm not trying to load a WebBrowser control. I don't want to have the JavaScript perform an AJAX call to a server. What I want to do is write unit tests in JavaScript and have then unit tests output JSON, even plain text would be fine. Then I want to have a generic C# class/executible that can load the file containing the JS, run the JS unit tests, scrap/load the results, and return a pass/fail with details during a post-build task. I think it's possible using the old ActiveX ScriptControl, but it seems like there ought to be a .NET way to do this without using SilverLight, the DLR, or anything else that hasn't shipped yet. Anyone have any ideas? update: From Brad Abrams blog namespace Microsoft.JScript.Vsa { [Obsolete("There is no replacement for this feature. Please see the ICodeCompiler documentation for additional help. http://go.microsoft.com/fwlink/?linkid=14202")] Clarification: We have unit tests for our JavaScript functions that are written in JavaScript using the JSUnit framework. Right now during our build process, we have to manually load a web page and click a button to ensure that all of the JavaScript unit tests pass. I'd like to be able to execute the tests during the post-build process when our automated C# unit tests are run and report the success/failure alongside of out C# unit tests and use them as an indicator as to whether or not the build is broken.

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  • Reference problem when returning an object from array in PHP

    - by avastreg
    I've a reference problem; the example should be more descriptive than me :P I have a class that has an array of objects and retrieve them through a key (string), like an associative array: class Collection { public $elements; function __construct() { $this->elements = array(); } public function get_element($key) { foreach($this->elements as $element) { if ($element->key == $key) { return $element; break; } } return null; } public function add_element ($element) { $this->elements[] = $element; } } Then i have an object (generic), with a key and some variables: class Element { public $key; public $another_var; public function __construct($key) { $this->key = $key; $this->another_var = "default"; } } Now, i create my collection: $collection = new Collection(); $collection->add_element(new Element("test1")); $collection->add_element(new Element("test2")); And then i try to change variable of an element contained in my "array": $element = $collection->get_element("test1"); $element->another_var = "random_string"; echo $collection->get_element("test1")->another_var; Ok, the output is random_string so i know that my object is passed to $element in reference mode. But if i do, instead: $element = $collection-get_element("test1"); $element = null; //or $element = new GenericObject(); $element-another_var = "bla"; echo $collection-get_element("test1")-another_var; the output is default like if it lost the reference. So, what's wrong? I have got the references to the variables of the element and not to the element itself? Any ideas?

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  • game currency convert: math efficient

    - by Comradsky
    For variables:4 text views named diamondText, goldText, silverText, and bronzeText;money variable unsigned int money;and an NSTimer, every .1 sec,runs function: -(void)updateMoney{ money++; bronzeText.text = [NSString stringWithFormat:@"%d",money]; silverText.text = [NSString stringWithFormat:@"%d",money%10]; goldText.text = [NSString stringWithFormat:@"%d",money%100]; diamondText.text= [NSString stringWithFormat:@"%d",money%1000]; } Given that my currency is diamond = 10 gold = 10 silver = 10 bronze = 1; What would be most efficient way to calculate and display the money labels? How would you store this variable, with GameCenter and NSDictionary or GameCenter and something else? More details are below if you don't understand. To clarify: bronze has the last 2 numbers, silver has the next 2 numbers, and so on. I understand I could use 4 ints or an array, but i would rather try to use this method, unless theres a much more efficient way. Example: When money = 1000;bronzeText = nothing, silverText = 10,goldText = nothing, diamondText = nothing; What other ways would you do this that you think would be more efficient? I will be calling a function (void)collisionDetector that detects if my player.frame crosses with a flyingObject.frame, and if that object is a coin it gives an added value to money and then calls (void)updateMoney. Im just using the timer to test this and spawn these flying objects.

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  • Unit testing a 'legacy' WPF Application

    - by sc_ray
    The product I have been working on has been in development for the past six years. It started as a generic data entry portal into an insanely complex part WPF/part legacy application. The system has been developed for all these years without a single Unit test in its fold. Now, the point has been raised for a comprehensive unit testing framework. I have been recruited recently to work on this product and have been tasked to get the 'Testing' in order. Since the team that worked on the product for the last six years adopted 'Agile', the project lacks any documentation of the business rules or any design documents. I have been trying to write unit tests for some of the modules. But I am not sure what to Mock, how to setup my Test fixture and eventually what to Test for, since a casual glance of the methods does not reveal its intentions. Also, it has come to my attention that the code was not developed with a particular methodology in mind. Given the situation, I was wondering if the good people of Stackoverflow could provide me with some advise on how to salvage this situation. I have heard about the book 'Working with Legacy Code' that has something to say about this general situation but I was thinking about getting some pointers from individuals who have encountered similar situations within the technology stack(C#,VB,C++,.NET 3.5,WCF,SQL Server 2005).

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  • XAML PixelGrid to Prevent Blurry Text

    - by Bodekaer
    Hi, Just wanted to share a small Grid I created, which can help prevent blurry text etc. as it adjusts the margin of the Grid to ensure a pixel perfect position and size of the grid. Works great e.g. for inside StackPanels with auto height Labels/TextBlocks. Here is the code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows; using System.Windows.Controls; using System.Windows.Media; namespace Controls { class PixelGrid : Grid { protected override void OnRenderSizeChanged(SizeChangedInfo sizeInfo) { // POSITION Vector position = VisualTreeHelper.GetOffset(this); double targetX = Math.Round(position.X, MidpointRounding.ToEven); double targetY = Math.Round(position.Y, MidpointRounding.ToEven); double marginLeft = targetX - position.X; double marginTop = targetY - position.Y; // SIZE double targetHeight = Math.Round(sizeInfo.NewSize.Height, MidpointRounding.ToEven); double targetWidth = Math.Round(sizeInfo.NewSize.Width, MidpointRounding.ToEven); double marginBottom = targetHeight - sizeInfo.NewSize.Height; double marginRight = targetWidth - sizeInfo.NewSize.Width; // Adjust margin to ensure pixel width this.Margin = new Thickness(marginLeft, marginTop, marginRight, marginBottom); base.OnRenderSizeChanged(sizeInfo); } } }

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  • Passing arguments and conditions to model in codeigniter

    - by stormdrain
    I'm adding some models to a project, and was wondering if there is a "best practice" kind of approach to creating models: Does it make sense to create a function for each specific query? I was starting to do this, then had the idea of creating a generic function that I could pass parameters to. e.g: Instead of function getClients(){ return $this->db->query('SELECT client_id,last FROM Names ORDER BY id DESC'); } function getClientNames($clid){ return $this->db->query('SELECT * FROM Names WHERE client_id = '.$clid); } function getClientName($nameID){ return $this->db->query('SELECT * FROM Names WHERE id ='.$nameID); } } Something like function getNameData($args,$cond){ if($cond==''){ $q=$this->db->query('SELECT '.$args.' FROM Names'); return $q; }else{ $q=$this->db->query('SELECT '.$args.' FROM Names WHERE '.$cond); return $q; } } where I can pass the fields and conditions (if applicable) to the model. Is there a reason the latter example would be a bad idea? Thanks!

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  • ViewController Navigating

    - by Kobe.o4
    I have 4 ViewControllers, startViewController as the initial View Controller. This contains my intro. After its finish, it will [self presentViewController:vc animated:YES completion:NULL]; into my menuViewController. startViewController ------> menuViewController ------> C1ViewController \ \ ------> ImportantViewController In my menuViewController are buttons for the two ViewController like the above illustration. Also I presented them in the View with this: [self presentViewController:vc animated:YES completion:NULL]; I return tomenuViewController with this [self dismissModalViewControllerAnimated:YES]; What I wanted is to make the ImportantViewController to be the like the parent view or the mainVIew even if I go to other Views. What I need is when ImportantViewController is presented when I go to either C1ViewController or menuViewController it wont be deallocated, or its content there will still be retained. Is it possible? And How? I don't know much about what parent and child view controllers for so I dont know what to implement in my problem. Thank you. BTW, Im using Storyboard.

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  • Google Anlytics event not firing

    - by yar1
    I am not getting and event data in GA. I installed Google Analytics Debugger Chrome extension and I see nothing happening (same goes when looking at Network panel in developer tools). I Googled it and read many (many) other answers and it looks like I'm doing things right. Page views, etc. are registering correctly... I have this code as the last thing before my closing tag: <script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','//www.google-analytics.com/analytics.js','ga'); ga('create', 'UA-MYREALCODE', 'mybna.net'); ga('send', 'pageview'); var _gaq = _gaq || []; _gaq.push(['_setAccount', 'UA-MYREALCODE']); _gaq.push(['_trackPageview']); </script> My event handlers are done using jQuery, all inside an external js file, loaded before the closing tag. For example: $(function () { $('#show-less').click(function (e) { pbr.showHideMore(e); _gaq.push(['_trackEvent', 'ShowMore', 'Hide', 'top button']); }); }); Any ideas anyone?

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  • Design issue when having classes implement different interfaces to restrict client actions

    - by devoured elysium
    Let's say I'm defining a game class that implements two different views: interface IPlayerView { void play(); } interface IDealerView { void deal(); } The view that a game sees when playing the game, and a view that the dealer sees when dealing the game (this is, a player can't make dealer actions and a dealer can't make player actions). The game definition is as following: class Game : IPlayerView, IDealerView { void play() { ... } void deal() { ... } } Now assume I want to make it possible for the players to play the game, but not to deal it. My original idea was that instead of having public Game GetGame() { ... } I'd have something like public IPlayerView GetGame() { ... } But after some tests I realized that if I later try this code, it works: IDealerView dealerView = (IDealerView)GameClass.GetGame(); this works as lets the user act as the dealer. Am I worrying to much? How do you usually deal with this patterns? I could instead make two different classes, maybe a "main" class, the dealer class, that would act as factory of player classes. That way I could control exactly what I would like to pass on the the public. On the other hand, that turns everything a bit more complex than with this original design. Thanks

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  • How do I call a variable from another class?

    - by squeezemylime
    I have a class called 'Constants' that I am storing a String variable in. This class contains a few global variables used in my app. I want to be able to reference this class and call the variable (called profileId) in other Views of my app. I looked around and found a few examples, but am not sure how to do this. Currently my setup is: Constants.h @interface Constants : UIViewController { NSString *profileId; } @property (nonatomic, retain) NSString *profileId; @end Constants.m #import "Constants.h" @implementation Constants @synthesize profileId; - (void)dealloc { [profileId release]; [super dealloc]; } And I am trying to call the variable profileId in a new View via this way: NewView.h file @class Constants; NewView.m file NSLog(@"ProfileId is:", [myConstants profileId]); Is there something I'm missing? It is coming up null, even though I am properly storing a value in it in another function via this way: Constants *Constant; Constant = [[Constants alloc] init]; Constant.profileId = userId;

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  • Rails - Update a single attribute : link with custom action or form with hidden fields?

    - by MrRuru
    Let's say I have a User model, with a facebook_uid field corresponding to the user's facebook id. I want to allow the user to unlink his facebook account. Do do so, I need to set this attribute to nil. I currently see 2 ways of doing this First way : create a custom action and link to it # app/controllers/users_controller.rb def unlink_facebook_account @user = User.find params[:id] # Authorization checks go here @user.facebook_uid = nil @user.save # Redirection go here end # config/routes.rb ressources :users do get 'unlink_fb', :on => :member, :as => unlink_fb end # in a view = link_to "Unlink your facebook account", unlink_fb_path(@user) Second way : create a form to the existing update action # app/views/user/_unlink_fb_form.html.haml = form_for @user, :method => "post" do |f| = f.hidden_field :facebook_uid, :value => nil = f.submit "Unlink Facebook account" I'm not a big fan of either way. In the first one, I have to add a new action for something that the update controller already can do. In the second one, I cannot set the facebook_uid to nil without customizing the update action, and I cannot have a link instead of a button without adding some javascript. Still, what would you recommend as the best and most elegant solution for this context? Did I miss a third alternative?

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  • Unknown ListView Behavior

    - by st0le
    I'm currently making a SMS Application in Android, the following is a code snippet from Inbox Listactivity, I have requested a cursor from the contentresolver and used a custom adapter to add custom views into the list. Now, in the custom view i've got 2 TextViews (tvFullBody,*tvBody*)... tvFullBody contains the Full SMS Text while tvBody contains a short preview (35 characters) The tvFullBody Visibility is by default set to GONE. My idea is, when the user clicks on a list item, the tvBody should dissappear(GONE) and the tvFullBody should become visible (VISIBLE). On Clicking again, it should revert back to its original state. //isExpanded is a BitSet of the size = no of list items...keeps track of which items are expanded and which are not @Override protected void onListItemClick(ListView l, View v, int position, long id) { if(isExpanded.get(position)) { v.findViewById(R.id.tvFullBody).setVisibility(View.GONE); v.findViewById(R.id.tvBody).setVisibility(View.VISIBLE); }else { v.findViewById(R.id.tvFullBody).setVisibility(View.VISIBLE); v.findViewById(R.id.tvBody).setVisibility(View.GONE); } isExpanded.flip(position); super.onListItemClick(l, v, position, id); } The Code works as it is supposed to :) except for an undesired sideeffect.... Every 10th (or so) List Item also gets "toggled". eg. If i Expand the 1st, then the 11th, 21th list items are also expanded...Although they remain off screen, but on scrolling you get to see the undesired "expansion". By my novice analysis, i'm guessing Listview keeps track of 10 list items that are currently visible, upon scrolling, it "reuses" those same variables, which is causing this problem...(i didn't check the android source code yet.) I'd be gratefull for any suggestion, on how i should tackle this! :) I'm open to alternative methods aswell....Thanks in advance! :)

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  • 2-column table with two foreign keys. Performance/design question.

    - by Emanuel
    Hello everyone! I recently ran into a quite complex problem and after looking around a lot I couldn't find a solution to it. I've found answers to my questions many times before on stackoverflow.com, so I decided to post here. So I'm making a user/group managment system for a web-based project, and I'm storing all related data into a postgreSQL database. This system relies on three tables: USERS GROUPS GROUP_USERS The two first tables simply define all the users and all the groups on the site, and the last table, GROUP_USERS, stores the groups every user is part of. It only has two columns: USER_ID GROUP_ID Since every user can be a member of several groups, I decided to make a separate table for this purpose, rather than storing a comma separated column in the USERS-table. Now, both columns are foreign keys, and I want to make them both primary keys as well, this since each combination of USER_ID and GROUP_ID has to be unique, and if I give them the constraint UNIQUE pgAdmin tells me that each table should have at least one Primary key. But now I am stuck with what seems to be a lot of indexes and relations to a very small table only containing numbers. In the end, I want this table to be as fast as possible, even if containing tens of thousands of rows. Size on disk shouldn't be a problem since its just all numbers anyway, but it feels quite stupid to have a full-sized index refering to a smaller table. Should I stick with my current solution, store comma-separated values in a column in the USERS-table or is there any other solution I should be aware of. PS. I don't want to use an array-column, even if they are supported by postgreSQL. I want to be as generic as possible so I can switch database later on, if necessary. EDIT: I other words, will using a compound primary key and two foreign keys in one table with only two columns have a negative impact on performance rather than the opposite due to the size of the generated index? Thank you!

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  • A Null Reference Exception

    - by Alex
    "Object reference not set to an instance of an object." using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.Graphics; namespace XNAdev { class Sprite { //The size of the Sprite public Rectangle Size; //Used to size the Sprite up or down from the original image public float Scale = 1.0f; //The current position of the Sprite public Vector2 Position = new Vector2(115, 0); //The texture object used when drawing the sprite private Texture2D mSpriteTexture; //Load the texture for the sprite using the Content Pipeline public void LoadContent(ContentManager theContentManager, string theAssetName) { mSpriteTexture = theContentManager.Load<Texture2D>(theAssetName); Size = new Rectangle(0, 0, (int)(mSpriteTexture.Width * Scale), (int)(mSpriteTexture.Height * Scale)); } //Draw the sprite to the screen public void Draw(SpriteBatch theSpriteBatch) { theSpriteBatch.Draw(mSpriteTexture, Position, new Rectangle(0, 0, mSpriteTexture.Width, mSpriteTexture.Height), Color.White, 0.0f, Vector2.Zero, Scale, SpriteEffects.None, 0); } } } I am very new at this C# so any help would be great. I have no idea what my error is.

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  • When to use pointer to a class and when to just instantiate it as a variable

    - by Enders
    Im sort of confused by it. The best I could find was reading through the cplusplus.com tutorial and all they have to say about pointers to classes. "It is perfectly valid to create pointers that point to classes. We simply have to consider that once declared, a class becomes a valid type, so we can use the class name as the type for the pointer" Which tells me nothing about when to use them over the normal instantiation. I've seen the - operator many times, and looked at some codes but cant really decipher why they did it. Generic examples will be appreciated; but more specifically related to gui programming. Its where I encountered it first. QGridLayout *mainLayout = new QGridLayout; mainLayout->addWidget(nameLabel, 0, 0); mainLayout->addWidget(nameLine, 0, 1); mainLayout->addWidget(addressLabel, 1, 0, Qt::AlignTop); mainLayout->addWidget(addressText, 1, 1); Why not QGridLayout mainLayout mainLayout.addWidget ... (It doesnt compile if I change the sample code to that and try it but you get the point) Thanks in advance

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  • Limiting a search to records from last_request_at...

    - by bgadoci
    I am trying to figure out how to display a count for records that have been created in a table since the last_request_at of a user. In my view I am counting the notes of a question with the following code: <% unless @questions.empty? %> <% @questions.each do |question| %> <%= h(question.notes.count) %> end end This is happening in the /views/users/show.html.erb file. Instead of counting all the notes for the question, I would only like to count the notes that have been created since the users last_request_at datetime. I don't neccessarily want to scope notes to display this 'new notes' count application wide, just simply in this one instance. To accomplish I am assuming I need to create a variable in the User#show action and call it in the view but not really sure how to do that. Other information you may need: class Note < ActiveRecord::Base belongs_to :user belongs_to :question end class Question < ActiveRecord::Base has_many :notes, :dependent => :destroy belongs_to :user end

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  • in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

    - by Steve
    Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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