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  • Right multi object dependance design

    - by kenny
    I need some help with a correct design. I have a class called BufferManager. The push() method of this class reads data from a source and pushes it to a buffer repeatedly until there is no more data left in the source. There are also consumer threads that read data from this buffer, as soon as new data arrives. There is an option to sort the data before it comes to buffer. What I do right now is that BufferManager, instead of pushing data to the buffer, pushes it to another "sorting" buffer and starts a sorting thread. SorterManager class reads the data, sorts it in files and push()es the sorted data into the buffer. There will be a bottleneck (I use merge sort with files) but this is something I can't avoid. This is a bad design, because both BufferManager and SorterManager push data to a buffer (that consumers read from). I think only BufferManager should do it. How can I design it?

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  • Silverlight 4 Twitter Client - Part 2

    - by Max
    We will create a few classes now to help us with storing and retrieving user credentials, so that we don't ask for it every time we want to speak with Twitter for getting some information. Now the class to sorting out the credentials. We will have this class as a static so as to ensure one instance of the same. This class is mainly going to include a getter setter for username and password, a method to check if the user if logged in and another one to log out the user. You can get the code here. Now let us create another class to facilitate easy retrieval from twitter xml format results for any queries we make. This basically involves just creating a getter setter for all the values that you would like to retrieve from the xml document returned. You can get the format of the xml document from here. Here is what I've in my Status.cs data structure class. using System; using System.Net; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; using System.Windows.Ink; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Animation; using System.Windows.Shapes;  namespace MaxTwitter.Classes { public class Status { public Status() {} public string ID { get; set; } public string Text { get; set; } public string Source { get; set; } public string UserID { get; set; } public string UserName { get; set; } } }  Now let us looking into implementing the Login.xaml.cs, first thing here is if the user is already logged in, we need to redirect the user to the homepage, this we can accomplish using the event OnNavigatedTo, which is fired when the user navigates to this particular Login page. Here you utilize the navigate to method of NavigationService to goto a different page if the user is already logged in. if (GlobalVariable.isLoggedin())         this.NavigationService.Navigate(new Uri("/Home", UriKind.Relative));  On the submit button click event, add the new event handler, which would save the perform the WebClient request and download the results as xml string. WebRequest.RegisterPrefix("https://", System.Net.Browser.WebRequestCreator.ClientHttp);  The following line allows us to create a web client to create a web request to a url and get back the string response. Something that came as a great news with SL 4 for many SL developers.   WebClient myService = new WebClient(); myService.AllowReadStreamBuffering = true; myService.UseDefaultCredentials = false; myService.Credentials = new NetworkCredential(TwitterUsername.Text, TwitterPassword.Password);  Here in the following line, we add an event that has to be fired once the xml string has been downloaded. Here you can do all your XLINQ stuff.   myService.DownloadStringCompleted += new DownloadStringCompletedEventHandler(TimelineRequestCompleted);   myService.DownloadStringAsync(new Uri("https://twitter.com/statuses/friends_timeline.xml"));  Now let us look at implementing the TimelineRequestCompleted event. Here we are not actually using the string response we get from twitter, I just use it to ensure the user is authenticated successfully and then save the credentials and redirect to home page. public void TimelineRequestCompleted(object sender, System.Net.DownloadStringCompletedEventArgs e) { if (e.Error != null) { MessageBox.Show("This application must be installed first"); }  If there is no error, we can save the credentials to reuse it later.   else { GlobalVariable.saveCredentials(TwitterUsername.Text, TwitterPassword.Password); this.NavigationService.Navigate(new System.Uri("/Home", UriKind.Relative)); } } Ok so now login page is done. Now the main thing – running this application. This credentials stuff would only work, if the application is run out of the browser. So we need fiddle with a few Silverlioght project settings to enable this. Here is how:    Right click on Silverlight > properties then check the "Enable running application out of browser".    Then click on Out-Of-Browser settings and check "Require elevated trust…" option. That's it, all done to run. Now press F5 to run the application, fix the errors if any. Then once the application opens up in browser with the login page, right click and choose install.  Once you install, it would automatically run and you can login and can see that you are redirected to the Home page. Here are the files that are related to this posts. We will look at implementing the Home page, etc… in the next post. Please post your comments and feedbacks; it would greatly help me in improving my posts!  Thanks for your time, catch you soon.

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  • Remove gravity from single body

    - by Siddharth
    I have multiple bodies in my game world in andengine. All the bodies affected by gravity but in that I want my specific body does not affected by the gravity. For that solution after research I found that I have to use body.setGravityScale(0) method for my problem solution. But in my andengine extension I don't found that method so please provide guidance about how get access about that method. Also for the above problem any other guidance will be acceptable. Thank You! I apply following code for reverse gravity final Vector2 vec = new Vector2(0, -SensorManager.GRAVITY_EARTH * bulletBody.getMass()); bulletBody.applyForce(vec, bulletBody.getWorldCenter());

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  • Building a plug-in for Windows Live Writer

    - by mbcrump
    This tutorial will show you how to build a plug-in for Windows Live Writer. Windows Live Writer is a blogging tool that Microsoft provides for free. It includes an open API for .NET developers to create custom plug-ins. In this tutorial, I will show you how easy it is to build one. Open VS2008 or VS2010 and create a new project. Set the target framework to 2.0, Application Type to Class Library and give it a name. In this tutorial, we are going to create a plug-in that generates a twitter message with your blog post name and a TinyUrl link to the blog post.  It will do all of this automatically after you publish your post. Once, we have a new projected created. We need to setup the references. Add a reference to the WindowsLive.Writer.Api.dll located in the C:\Program Files (x86)\Windows Live\Writer\ folder, if you are using X64 version of Windows. You will also need to add a reference to System.Windows.Forms System.Web from the .NET tab as well. Once that is complete, add your “using” statements so that it looks like whats shown below: Live Writer Plug-In "Using" using System; using System.Collections.Generic; using System.Text; using WindowsLive.Writer.Api; using System.Web; Now, we are going to setup some build events to make it easier to test our custom class. Go into the Properties of your project and select Build Events, click edit the Post-build and copy/paste the following line: XCOPY /D /Y /R "$(TargetPath)" "C:\Program Files (x86)\Windows Live\Writer\Plugins\" Your screen should look like the one pictured below: Next, we are going to launch an external program on debug. Click the debug tab and enter C:\Program Files (x86)\Windows Live\Writer\WindowsLiveWriter.exe Your screen should look like the one pictured below:   Now we have a blank project and we need to add some code. We start with adding the attributes for the Live Writer Plugin. Before we get started creating the Attributes, we need to create a GUID. This GUID will uniquely identity our plug-in. So, to create a GUID follow the steps in VS2008/2010. Click Tools from the VS Menu ->Create GUID It will generate a GUID like the one listed below: GUID <Guid("56ED8A2C-F216-420D-91A1-F7541495DBDA")> We only want what’s inside the quotes, so your final product should be: "56ED8A2C-F216-420D-91A1-F7541495DBDA". Go ahead and paste this snipped into your class just above the public class. Live Writer Plug-In Attributes [WriterPlugin("56ED8A2C-F216-420D-91A1-F7541495DBDA",    "Generate Twitter Message",    Description = "After your new post has been published, this plug-in will attempt to generate a Twitter status messsage with the Title and TinyUrl link.",    HasEditableOptions = false,    Name = "Generate Twitter Message",    PublisherUrl = "http://michaelcrump.net")] [InsertableContentSource("Generate Twitter Message")] So far, it should look like the following: Next, we need to implement the PublishNotifcationHook class and override the OnPostPublish. I’m not going to dive into what the code is doing as you should be able to follow pretty easily. The code below is the entire code used in the project. PublishNotificationHook public class Class1 :  PublishNotificationHook  {      public override void OnPostPublish(System.Windows.Forms.IWin32Window dialogOwner, IProperties properties, IPublishingContext publishingContext, bool publish)      {          if (!publish) return;          if (string.IsNullOrEmpty(publishingContext.PostInfo.Permalink))          {              PluginDiagnostics.LogError("Live Tweet didn't execute, due to blank permalink");          }          else          {                var strBlogName = HttpUtility.UrlEncode("#blogged : " + publishingContext.PostInfo.Title);  //Blog Post Title              var strUrlFinal = getTinyUrl(publishingContext.PostInfo.Permalink); //Blog Permalink URL Converted to TinyURL              System.Diagnostics.Process.Start("http://twitter.com/home?status=" + strBlogName + strUrlFinal);            }      } We are going to go ahead and create a method to create the short url (tinyurl). TinyURL Helper Method private static string getTinyUrl(string url) {     var cmpUrl = System.Globalization.CultureInfo.InvariantCulture.CompareInfo;     if (!cmpUrl.IsPrefix(url, "http://tinyurl.com"))     {         var address = "http://tinyurl.com/api-create.php?url=" + url;         var client = new System.Net.WebClient();         return (client.DownloadString(address));     }     return (url); } Go ahead and build your project, it should have copied the .DLL into the Windows Live Writer Plugin Directory. If it did not, then you will want to check your configuration. Once that is complete, open Windows Live Writer and select Tools-> Options-> Plug-ins and enable your plug-in that you just created. Your screen should look like the one pictured below: Go ahead and click OK and publish your blog post. You should get a pop-up with the following: Hit OK and It should open a Twitter and either ask for a login or fill in your status as shown below:   That should do it, you can do so many other things with the API. I suggest that if you want to build something really useful consult the MSDN pages. This plug-in that I created was perfect for what I needed and I hope someone finds it useful.

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  • Methodology for Documenting Existing Code Base

    - by George Stocker
    I work as part of a team on an existing application that has no inline documentation, nor does it have technical documentation. As I've been working on various bug reports on the application, I've written a sort of breadcrumb trail for myself - bug numbers in various places so that the next developer can refer to that bug number to see what was going on. My question is thus: What is the most effecient method for documenting this code? Should I document as I touch the area (the virus method, if you will), or should I document from each section on its own, and not follow paths that branch out into other areas of the application? Should I insert inline comments where none previously existed (with the fear that I may end up incorrectly identifying what the code does)? What method would you use to accurately and quickly document a rather large application that has no existing inline documentation, nor inline references to external documentation?

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  • Deterministic Multiplayer RTS game questions?

    - by Martin K
    I am working on a cross-platform multiplayer RTS game where the different clients and a server(flash and C#), all need to stay deterministically synchronised. To deal with Floatpoint inconsistencies, I've come across this method: http://joshblog.net/2007/01/30/flash-floating-point-number-errors/#comment-49912 which basically truncates off the nondeterministic part: return Math.round(1000 * float) / 1000; Howewer my concern is that every time there is a division, there is further chance of creating additional floatpoint errors, in essence making it worse? . So it occured to me, how about something like this: function floatSafe(number:Number) : Number {return Math.round(float* 1024) / 1024; } ie dividing with only powers of 2 ? What do you think? . Ironically with the above method I got less accurate results: trace( floatSafe(3/5) ) // 0.599609375 where as with the other method(dividing with 1000), or just tracing the raw value I am getting 3/5 = 0.6 or Maybe thats what 3/5 actually is, IE 0.6 cannot really be represented with a floatpoint datatype, and would be more consistent across different platforms?

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  • Python response parse [migrated]

    - by Pavel Shevelyov
    When I'm sending some data on host: r = urllib2.Request(url, data = data, headers = headers) page = urllib2.urlopen(r) print page.read() I have something like this: [{"command":"settings","settings":{"basePath":"\/","ajaxPageState":{"theme":"spsr","theme_token":"kRHUhchUVpxAMYL8Y8IoyYIcX0cPrUstziAi8gSmMYk","css":[]},"ajax":{"edit-submit":{"callback":"spsr_calculator_form_ajax","wrapper":"calculator_form","method":"replaceWith","event":"mousedown","keypress":true,"url":"\/ru\/system\/ajax","submit":{"_triggering_element_name":"submit"}}}},"merge":true},{"command":"insert","method":null,"selector":null,"data":"\u003cdiv id=\"calculator_form\"\u003e\u003cform action=\"\/ru\/service\/calculator\" method=\"post\" id=\"spsr-calculator-form\" accept-charset=\"UTF-8\"\u003e\u003cdiv\u003e\u003cinput id=\"edit-from-ship-region-id\" type=\"hidden\" name=\"from_ship_region_id\" value=\"\" \/\u003e\n\u003cinput type=\"hidden\" name=\"form_build_id\" value=\"form-0RK_WFli4b2kUDTxpoqsGPp14B_0yf6Fz9x7UK-T3w8\" \/\u003e\n\u003cinput type=\"hidden\" name=\"form_id\" value=\"spsr_calculator_form\" \/\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"bg_p\"\u003e \n\u0421\u0435\u0439\u0447\u0430\u0441 \u0412\u044b... bla bla bla but I want have something, like this: <html><h1>bla bla bla</h1></html> How can I do it?

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  • How can I gain access to a player instance in a Minecraft mod?

    - by Andrew Graber
    I'm creating Minecraft mod with a pickaxe that takes away experience when you break a block. The method for taking away experience from a player is addExperience on EntityPlayer, so I need to get an instance of EntityPlayer for the player using my pickaxe when the pickaxe breaks a block, so that I can remove the appropriate amount of experience. My pickaxe class currently looks like this: public class ExperiencePickaxe extends ItemPickaxe { public ExperiencePickaxe(int ItemID, EnumToolMaterial material){ super(ItemID, material); } public boolean onBlockDestroyed(ItemStack par1ItemStack, World par2World, int par3, int par4, int par5, int par6, EntityLiving par7EntityLiving) { if ((double)Block.blocksList[par3].getBlockHardness(par2World, par4, par5, par6) != 0.0D) { EntityPlayer e = new EntityPlayer(); // create an instance e.addExperience(-1); } return true; } } Obviously, I cannot actually create a new EntityPlayer since it is an abstract class. How can I get access to the player using my pickaxe?

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  • Intentional misspellings to avoid reserved words

    - by Renesis
    I often see code that include intentional misspellings of common words that for better or worse have become reserved words: klass or clazz for class: Class clazz = ThisClass.class kount for count in SQL: count(*) AS kount Personally I find this decreases readability. In my own practice I haven't found too many cases where a better name couldn't have been used — itemClass or recordTotal. However, it's so common that I can't help but wonder if I'm the only one? Anyone have any advice or even better, quoted recommendations from well-respected programmers on this practice?

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  • Area of testing

    - by ?????? ??????????
    I'm trying to understand which part of my code I should to test. I have some code. Below is example of this code, just to understand the idea. Depends of some parametrs I put one or another currency to "Event" and return his serialization in the controller. Which part of code I should to test? Just the final serialization, or only "Event" or every method: getJson, getRows, fillCurrency, setCurrency? class Controller { public function getJson() { $rows = $eventManager->getRows(); return new JsonResponse($rows); } } class EventManager { public function getRows() { //some code here if ($parameter == true) { $this->fillCurrency($event, $currency); } } public function fillCurrency($event, $currency) { //some code here if ($parameters == true) { $event->setCurrency($currency); } } } class Event { public function setCurrency($currency) { $this->updatedAt = new Datetime(); $this->currency = $currency; } }

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  • Wifi problem in ubuntu using macbook pro when it restart

    - by Amro
    I was read that subject : http://ubuntuforums.org/showthread.php?t=2011756 and i follow it step by step in the page n 1 , then i was connect but after i restart my macbook again , i was lost the wifi connection.i dont know why or whats the problem exactly. every time I run this command: dmesg | grep -e b43 -e bcma I get this output: [ 2012.769684] bcma-pci-bridge 0000:02:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17 [ 2012.769701] bcma-pci-bridge 0000:02:00.0: setting latency timer to 64 [ 2012.769775] bcma: Core 0 found: ChipCommon (manuf 0x4BF, id 0x800, rev 0x25, class 0x0) [ 2012.769808] bcma: Core 1 found: IEEE 802.11 (manuf 0x4BF, id 0x812, rev 0x1D, class 0x0) [ 2012.769889] bcma: Core 2 found: PCIe (manuf 0x4BF, id 0x820, rev 0x13, class 0x0) [ 2012.770175] bcma: PMU resource config unknown for device 0x4331 [ 2012.824527] bcma: Bus registered [ 2012.831744] b43-phy0: Broadcom 4331 WLAN found (core revision 29) [ 2013.371031] b43-phy0: Loading firmware version 666.2 (2011-02-23 01:15:07) and to get the connection again every time i must entery that code in the step of reload driver. How i can let the ubuntu see my wifi and wireless device automatically when i reboot my computer????

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  • Migrating Core Data to new UIManagedDocument in iOS 5

    - by samerpaul
    I have an app that has been on the store since iOS 3.1, so there is a large install base out there that still uses Core Data loaded up in my AppDelegate. In the most recent set of updates, I raised the minimum version to 4.3 but still kept the same way of loading the data. Recently, I decided it's time to make the minimum version 5.1 (especially with 6 around the corner), so I wanted to start using the new fancy UIManagedDocument way of using Core Data. The issue with this though is that the old database file is still sitting in the iOS app, so there is no migrating to the new document. You have to basically subclass UIManagedDocument with a new model class, and override a couple of methods to do it for you. Here's a tutorial on what I did for my app TimeTag.  Step One: Add a new class file in Xcode and subclass "UIManagedDocument" Go ahead and also add a method to get the managedObjectModel out of this class. It should look like:   @interface TimeTagModel : UIManagedDocument   - (NSManagedObjectModel *)managedObjectModel;   @end   Step two: Writing the methods in the implementation file (.m) I first added a shortcut method for the applicationsDocumentDirectory, which returns the URL of the app directory.  - (NSURL *)applicationDocumentsDirectory {     return [[[NSFileManagerdefaultManager] URLsForDirectory:NSDocumentDirectoryinDomains:NSUserDomainMask] lastObject]; }   The next step was to pull the managedObjectModel file itself (.momd file). In my project, it's called "minimalTime". - (NSManagedObjectModel *)managedObjectModel {     NSString *path = [[NSBundlemainBundle] pathForResource:@"minimalTime"ofType:@"momd"];     NSURL *momURL = [NSURL fileURLWithPath:path];     NSManagedObjectModel *managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:momURL];          return managedObjectModel; }   After that, I need to check for a legacy installation and migrate it to the new UIManagedDocument file instead. This is the overridden method: - (BOOL)configurePersistentStoreCoordinatorForURL:(NSURL *)storeURL ofType:(NSString *)fileType modelConfiguration:(NSString *)configuration storeOptions:(NSDictionary *)storeOptions error:(NSError **)error {     // If legacy store exists, copy it to the new location     NSURL *legacyPersistentStoreURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"minimalTime.sqlite"];          NSFileManager* fileManager = [NSFileManagerdefaultManager];     if ([fileManager fileExistsAtPath:legacyPersistentStoreURL.path])     {         NSLog(@"Old db exists");         NSError* thisError = nil;         [fileManager replaceItemAtURL:storeURL withItemAtURL:legacyPersistentStoreURL backupItemName:niloptions:NSFileManagerItemReplacementUsingNewMetadataOnlyresultingItemURL:nilerror:&thisError];     }          return [superconfigurePersistentStoreCoordinatorForURL:storeURL ofType:fileType modelConfiguration:configuration storeOptions:storeOptions error:error]; }   Basically what's happening above is that it checks for the minimalTime.sqlite file inside the app's bundle on the iOS device.  If the file exists, it tells you inside the console, and then tells the fileManager to replace the storeURL (inside the method parameter) with the legacy URL. This basically gives your app access to all the existing data the user has generated (otherwise they would load into a blank app, which would be disastrous). It returns a YES if successful (by calling it's [super] method). Final step: Actually load this database Due to how my app works, I actually have to load the database at launch (instead of shortly after, which would be ideal). I call a method called loadDatabase, which looks like this: -(void)loadDatabase {     static dispatch_once_t onceToken;          // Only do this once!     dispatch_once(&onceToken, ^{         // Get the URL         // The minimalTimeDB name is just something I call it         NSURL *url = [[selfapplicationDocumentsDirectory] URLByAppendingPathComponent:@"minimalTimeDB"];         // Init the TimeTagModel (our custom class we wrote above) with the URL         self.timeTagDB = [[TimeTagModel alloc] initWithFileURL:url];           // Setup the undo manager if it's nil         if (self.timeTagDB.undoManager == nil){             NSUndoManager *undoManager = [[NSUndoManager  alloc] init];             [self.timeTagDB setUndoManager:undoManager];         }                  // You have to actually check to see if it exists already (for some reason you can't just call "open it, and if it's not there, create it")         if ([[NSFileManagerdefaultManager] fileExistsAtPath:[url path]]) {             // If it does exist, try to open it, and if it doesn't open, let the user (or at least you) know!             [self.timeTagDB openWithCompletionHandler:^(BOOL success){                 if (!success) {                     // Handle the error.                     NSLog(@"Error opening up the database");                 }                 else{                     NSLog(@"Opened the file--it already existed");                     [self refreshData];                 }             }];         }         else {             // If it doesn't exist, you need to attempt to create it             [self.timeTagDBsaveToURL:url forSaveOperation:UIDocumentSaveForCreatingcompletionHandler:^(BOOL success){                 if (!success) {                     // Handle the error.                     NSLog(@"Error opening up the database");                 }                 else{                     NSLog(@"Created the file--it did not exist");                     [self refreshData];                 }             }];         }     }); }   If you're curious what refreshData looks like, it sends out a NSNotification that the database has been loaded: -(void)refreshData {     NSNotification* refreshNotification = [NSNotificationnotificationWithName:kNotificationCenterRefreshAllDatabaseData object:self.timeTagDB.managedObjectContext  userInfo:nil];     [[NSNotificationCenter defaultCenter] postNotification:refreshNotification];     }   The kNotificationCenterRefreshAllDatabaseData is just a constant I have defined elsewhere that keeps track of all the NSNotification names I use. I pass the managedObjectContext of the newly created file so that my view controllers can have access to it, and start passing it around to one another. The reason we do this as a Notification is because this is being run in the background, so we can't know exactly when it finishes. Make sure you design your app for this! Have some kind of loading indicator, or make sure your user can't attempt to create a record before the database actually exists, because it will crash the app.

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  • Switching between levels, re-initialize existing structure or create new one?

    - by Martino Wullems
    This is something I've been wondering for quite a while. When building games that exist out of multiple levels (platformers, shmups etc) what is the prefered method to switch between the levels? Let's say we have a level class that does the following: Load data for the level design (tiles), enemies, graphics etc. Setup all these elements in their appriopate locations and display them Start physics and game logic I'm stuck between the following 2 methods: 1: Throw away everything in the level class and make a new one, we have to load an entirely new level anyway! 2: pause the game logic and physics, unload all currents assets, then re-initialize those components with the level data for the new level. They both have their pros and cons. Method 1 is alot easier and seems to make sense since we have to redo everything anyway. But method 2 allows you to re-use exisiting elements which might save resources and allows for a smoother transfer to the new level.

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  • Material, Pass, Technique and shaders

    - by Papi75
    I'm trying to make a clean and advanced Material class for the rendering of my game, here is my architecture: class Material { void sendToShader() { program->sendUniform( nameInShader, valueInMaterialOrOther ); } private: Blend blendmode; ///< Alpha, Add, Multiply, … Color ambient; Color diffuse; Color specular; DrawingMode drawingMode; // Line Triangles, … Program* program; std::map<string, TexturePacket> textures; // List of textures with TexturePacket = { Texture*, vec2 offset, vec2 scale} }; How can I handle the link between the Shader and the Material? (sendToShader method) If the user want to send additionals informations to the shader (like time elapsed), how can I allow that? (User can't edit Material class) Thanks!

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  • yield – Just yet another sexy c# keyword?

    - by George Mamaladze
    yield (see NSDN c# reference) operator came I guess with .NET 2.0 and I my feeling is that it’s not as wide used as it could (or should) be.   I am not going to talk here about necessarity and advantages of using iterator pattern when accessing custom sequences (just google it).   Let’s look at it from the clean code point of view. Let's see if it really helps us to keep our code understandable, reusable and testable.   Let’s say we want to iterate a tree and do something with it’s nodes, for instance calculate a sum of their values. So the most elegant way would be to build a recursive method performing a classic depth traversal returning the sum.           private int CalculateTreeSum(Node top)         {             int sumOfChildNodes = 0;             foreach (Node childNode in top.ChildNodes)             {                 sumOfChildNodes += CalculateTreeSum(childNode);             }             return top.Value + sumOfChildNodes;         }     “Do One Thing” Nevertheless it violates one of the most important rules “Do One Thing”. Our  method CalculateTreeSum does two things at the same time. It travels inside the tree and performs some computation – in this case calculates sum. Doing two things in one method is definitely a bad thing because of several reasons: ·          Understandability: Readability / refactoring ·          Reuseability: when overriding - no chance to override computation without copying iteration code and vice versa. ·          Testability: you are not able to test computation without constructing the tree and you are not able to test correctness of tree iteration.   I want to spend some more words on this last issue. How do you test the method CalculateTreeSum when it contains two in one: computation & iteration? The only chance is to construct a test tree and assert the result of the method call, in our case the sum against our expectation. And if the test fails you do not know wether was the computation algorithm wrong or was that the iteration? At the end to top it all off I tell you: according to Murphy’s Law the iteration will have a bug as well as the calculation. Both bugs in a combination will cause the sum to be accidentally exactly the same you expect and the test will PASS. J   Ok let’s use yield! That’s why it is generally a very good idea not to mix but isolate “things”. Ok let’s use yield!           private int CalculateTreeSumClean(Node top)         {             IEnumerable<Node> treeNodes = GetTreeNodes(top);             return CalculateSum(treeNodes);         }             private int CalculateSum(IEnumerable<Node> nodes)         {             int sumOfNodes = 0;             foreach (Node node in nodes)             {                 sumOfNodes += node.Value;             }             return sumOfNodes;         }           private IEnumerable<Node> GetTreeNodes(Node top)         {             yield return top;             foreach (Node childNode in top.ChildNodes)             {                 foreach (Node currentNode in GetTreeNodes(childNode))                 {                     yield return currentNode;                 }             }         }   Two methods does not know anything about each other. One contains calculation logic another jut the iteration logic. You can relpace the tree iteration algorithm from depth traversal to breath trevaersal or use stack or visitor pattern instead of recursion. This will not influence your calculation logic. And vice versa you can relace the sum with product or do whatever you want with node values, the calculateion algorithm is not aware of beeng working on some tree or graph.  How about not using yield? Now let’s ask the question – what if we do not have yield operator? The brief look at the generated code gives us an answer. The compiler generates a 150 lines long class to implement the iteration logic.       [CompilerGenerated]     private sealed class <GetTreeNodes>d__0 : IEnumerable<Node>, IEnumerable, IEnumerator<Node>, IEnumerator, IDisposable     {         ...        150 Lines of generated code        ...     }   Often we compromise code readability, cleanness, testability, etc. – to reduce number of classes, code lines, keystrokes and mouse clicks. This is the human nature - we are lazy. Knowing and using such a sexy construct like yield, allows us to be lazy, write very few lines of code and at the same time stay clean and do one thing in a method. That's why I generally welcome using staff like that.   Note: The above used recursive depth traversal algorithm is possibly the compact one but not the best one from the performance and memory utilization point of view. It was taken to emphasize on other primary aspects of this post.

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  • Is conditional return type ever a good idea?

    - by qegal
    So I have a method that's something like this: -(BOOL)isSingleValueRecord And another method like this: -(Type)typeOfSingleValueRecord And it occurred to me that I could combine them into something like this: -(id)isSingleValueRecord And have the implementation be something like this: -(id)isSingleValueRecord { //If it is single value if(self.recordValue = 0) { //Do some stuff to determine type, then return it return typeOfSingleValueRecord; } //If its not single value else { //Return "NO" return [NSNumber numberWithBool:NO]; } } So combining the two methods makes it more efficient but makes the readability go down. In my gut, I feel like I should go with the two-method version, but is that really right? Is there any case that I should go with the combined version?

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  • Is nesting types considered bad practice?

    - by Rob Z
    As noted by the title, is nesting types (e.g. enumerated types or structures in a class) considered bad practice or not? When you run Code Analysis in Visual Studio it returns the following message which implies it is: Warning 34 CA1034 : Microsoft.Design : Do not nest type 'ClassName.StructueName'. Alternatively, change its accessibility so that it is not externally visible. However, when I follow the recommendation of the Code Analysis I find that there tend to be a lot of structures and enumerated types floating around in the application that might only apply to a single class or would only be used with that class. As such, would it be appropriate to nest the type sin that case, or is there a better way of doing it?

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  • What should I call the process of converting an object to a string?

    - by shabbychef
    We are having a game of 'semantic football' in the office over this matter: I am writing a method for an object which will represent the object as a string. That string should be such that when typed (more likely, cut and pasted) into the interpreter window (I will keep the language name out of this for now), will produce an object which is, for our purposes, identical to the one upon which the method was called. There is a spirited discussion over the 'best' name for this method. The terms pickle, serialize, deflate, etc have been proposed. However, it seems that those terms assume some process for the de-pickling (unserialization, etc) that is not necessarily the language interpreter itself. That is, they do not specifically refer to the case where strings of valid code are produced. This is closer to a quine, but we are re-producing the object not the code, so this is not quite right. any suggestions?

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  • What's the equivalent name of "procedure" in OOP?

    - by AeroCross
    In several of my programming courses in the University, my teachers always told me the following: A function and a procedure are basically the same thing: the only difference is that a function returns a value, and the procedure doesn't. That means that this: function sum($a, $b) { return $a + $b; } ... is a function, and this: function sum($a, $b) { echo $a + $b; } ... is a procedure. In the same train of thought, I've seen that a method is the equivalent of a function in the OOP world. That means that this: class Example { function sum($a, $b) { return $a + $b; } } Is a method — but how do you call this? class Example { function sum($a, $b) { echo $a + $b; } } What's the equivalent name, or how do you call a method that doesn't returns anything?

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  • Resolving an App-Relative URL without a Page Object Reference

    - by Damon
    If you've worked with ASP.NET before then you've almost certainly seen an application-relative URL like ~/SomeFolder/SomePage.aspx.  The tilde at the beginning is a stand in for the application path, and it can easily be resolved using the Page object's ResolveUrl method: string url = Page.ResolveUrl("~/SomeFolder/SomePage.aspx"); There are times, however, when you don't have a page object available and you need to resolve an application relative URL.  Assuming you have an HttpContext object available, the following method will accomplish just that: public static string ResolveAppRelativeUrl(string url) {      return url.Replace("~", System.Web.HttpContext.Current.Request.ApplicationPath); } It just replaces the tilde with the application path, which is essentially all the ResolveUrl method does.

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  • Silverlight Reporting Application Part 3.5 - Prism Background and WCF RIA [Series Intermission]

    Taking a step back before I dive into the details and full-on coding fun, I wanted to once again respond to a comment on my last post to clear up some things in regards to how I'm setting up my project and some of the choices I've made. Aka, thanks Ben. :) Prism Project Setup For starters, I'm not the ideal use case for a Prism application. In most cases where you've got a one-man team, Prism can be overkill as it is more intended for large teams who are geographically dispersed or in applications that have a larger scale than my Recruiting application in which you'll greatly benefit from modularity, delayed loading of xaps, etc. What Prism offers, though, is a manner for handling UI, commands, and events with the idea that, through a modular approach in which no parts really need to know about one another, I can update this application bit by bit as hiring needs change or requirements differ between offices without having to worry that changing something in the Jobs module will break something in, say, the Scheduling module. All that being said, here's a look at how our project breakdown for Recruit (MVVM/Prism implementation) looks: This could be a little misleading though, as each of those modules is actually another project in the overall Recruit solution. As far as what the projects actually are, that looks a bit like this: Recruiting Solution Recruit (Shell up there) - Main Silverlight Application .Web - Default .Web application to host the Silverlight app Infrastructure - Silverlight Class Library Project Modules - Silverlight Class Library Projects Infrastructure &Modules The Infrastructure project is probably something you'll see to some degree in any composite application. In this application, it is going to contain custom commands (you'll see the joy of these in a post or two down the road), events, helper classes, and any custom classes I need to share between different modules. Think of this as a handy little crossroad between any parts of your application. Modules on the other hand are the bread and butter of this application. Besides the shell, which holds the UI skeleton, and the infrastructure, which holds all those shared goodies, the modules are self-contained bundles of functionality to handle different concerns. In my scenario, I need a way to look up and edit Jobs, Applicants, and Schedule interviews, a Notification module to handle telling the user when different things are happening (i.e., loading from database), and a Menu to control interaction and moving between different views. All modules are going to follow the following pattern: The module class will inherit from IModule and handle initialization and loading the correct view into the correct region, whereas the Views and ViewModels folders will contain paired Silverlight user controls and ViewModel class backings. WCF RIA Services Since we've got all the projects in a single solution, we did not have to go the route of creating a WCR RIA Services Class Library. Every module has it's WCF RIA link back to the main .Web project, so the single Linq-2-SQL (yes, I said Linq-2-SQL, but I'll soon be switching to OpenAccess due to the new visual designer) context I'm using there works nicely with the scope of my project. If I were going for completely separating this project out and doing different, dynamically loaded elements, I'd probably go for the separate class library. Hope that clears that up. In the future though, I will be using that in a project that I've got in the "when I've got enough time to work on this" pipeline, so we'll get into that eventually- and hopefully when WCF RIA is in full release! Why Not use Silverlight Navigation/Business Template? The short answer- I'm a creature of habit, and having used Silverlight for a few years now, I'm used to doing lots of things manually. :) Plus, starting with a blank slate of a project I'm able to set up things exactly as I want them to be. In this case, rather than the navigation frame we would see in one of the templates, the MainRegion/ContentControl is working as our main navigation window. In many cases I will use theSilverlight navigation template to start things off, however in this case I did not need those features so I opted out of using that. Next time when I actually hit post #4, we're going to get into the modules and starting to get functionality into this application. Next week is also release week for the Q1 2010 release, so be sure to check out our annualWebinar Week (I might be biased, but Wednesday is my favorite out of the group). Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Is is common to use the command pattern for property get/sets?

    - by k rey
    Suppose I have a controller class with a bunch of properties. Each time a property is changed, I would like to update the model. Now also suppose that I use the command pattern to perform model updates. Is it common to use command classes within property get and sets of the controller class or is there a better way? Here is an example of what I am currently using: class MyController { private int _myInt; public int MyInt { get { return _myInt; } set { MyCommand cmd = new MyCommand(); cmd.Argument = _myInt; cmd.Execute(); // Command object updates the model } } }

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  • RequestContextHolder.currentRequestAttributes() and accessing HTTP Session

    - by Umesh Awasthi
    Need to access HTTP session for fetching as well storing some information.I am using Spring-MVC for my application and i have 2 options here. User Request/ Session in my Controller method and do my work Use RequestContextHolde to access Session information. I am separating some calculation logic from Controller and want to access Session information in this new layer and for that i have 2 options Pass session or Request object to other method in other layer and perform my work. use RequestContextHolder.currentRequestAttributes() to access request/ session and perform my work. I am not sure which is right way to go? with second approach, i can see that method calling will be more clean and i need not to pass request/ session each time.

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  • How are generics implemented?

    - by greenoldman
    This is the question from compiler internals perspective. I am interested in generics, not templates (C++), so I marked the question with C#. Not Java, because AFAIK the generics in both languages differ in implementations. When I look at languages w/o generics it is pretty straightforward, you can validate the class definition, add it to hierarchy and that's it. But what to do with generic class, and more importantly how handle references to it? How to make sure that static fields are singular per instantiations (i.e. each time generic parameters are resolved). Let's say I see a call: var x = new Foo<Bar>(); Do I add new Foo_Bar class to hierarchy? Update: So far I found only 2 relevant posts, however even they don't go into much details in sense "how to do it by yourself": http://www.jprl.com/Blog/archive/development/2007/Aug-31.html http://www.artima.com/intv/generics2.html

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  • What is it going here in my solution?

    - by bbb
    I am a asp.net mvc programmer and if I want to start a project I do this: I make a class library named Model for my models. I make a class library named Infrastructure.Repository for database processes I make a class library named Application for business logic layer And finally I make a MVC project for the UI. But now some things are confusing me. Am I using 3-tier programming? If yes so what is n-tier programming and which one is better? If no so what is 3-tier programming? Some where I see that the tiers namings are DAL and BIZ. Which one is correct according to the naming convention?

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