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• Changing Your Design for Testability

  Sometimes I come across a way of putting something that it is pithy good, not Hallmark trite, but an impactful and concise way of clarifying a previously obscure concept. A recent one of these happy occurrences was when I was reading the excellent Art of Unit Testing by Roy Osherove. After going through the basics of why youd want to test code and how to do it, Roy confronts a frequent objection to having unit tests, that it ends up changing how you design your components: When we write unit tests for our code, we are adding another end user (the test) to the object model. That end user is just as important as the original one, but it has different goals when using the model.  The test has specific requirements from the object model that seem to defy the basic logic behind a couple of object-oriented principles, mainly encapsulation. [emphasis added by me] When I read this, something clicked for me. I used to find it persuasive that because unit tests caused you to change your design they were more disruptive than they were worth. The counter argument I heard is that the disruption was OK, because testable design was just obviously better. That argument was not convincing as it seemed like delusional arrogance to suggest that any one of type of design was just inherently better for the particular applications I was building. What was missing was that I was not thinking of unit tests as an additional and equal end user to my design. If I accepted that proposition, than it was indeed obvious that a testable design was better because now all users of my component would be satisfied. Have I accepted that proposition? Id phrase it slightly different. I find more and more that having unit tests helps me write better, less buggy code before it gets to production or QA. As I write more unit tests, it gets easier to see how to create testable components, so I dont feel like its taking me as much extra time up front. I pick and choose components that seem most likely to benefit from automated tests and it is working out nicely. If you already implement Test Driven Development, this whole post was probably a waste of your time <g> If you hate the idea of unit tests, well, probably not a great value prop for you either. However, if you are somewhere in between, at least take a minute and check out a sample chapter from Roys book at: http://www.manning.com/osherove/.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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• design practice for business layer when supporting API versioning

  - by user1186065

  Is there any design pattern or practice recommended for business layer when dealing with multiple API version. For example, I have something like this. http://site.com/blogs/v1/?count=10 which calls business object method GetAllBlogs(int count) to get information http://site.com/blogs/v2/?blog_count=20 which calls business object method GetAllBlogs_v2(int blogCounts) Since parameter name is changed, I created another business method for version 2. This is just one example but it could have other breaking changes for which it requires me to create another method to support both version. Is there any design pattern or best practice for business/data access layer I should follow when supporting API Versioning?

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• Delay command execution over sockets

  - by David

  I've been trying to fix the game loop in a real time (tick delay) MUD. I realized using Thread.Sleep would seem clunky when the user spammed commands through their choice of client (Zmud, etc) e.g. east;south;southwest would wait three move ticks and then output everything from the past couple rooms. The game loop basically calls a Flush and Fill method for each socket during each tick (50ms) private void DoLoop() { Stopwatch stopWatch = new Stopwatch(); stopWatch.Start(); while (running) { // for each socket, flush and fill ConnectionMonitor.Update(); stopWatch.Stop(); WaitIfNeeded(stopWatch.ElapsedMilliseconds); stopWatch.Reset(); } } The Fill method fires the command events, but as mentioned before, they currently block using Thread.Sleep. I tried adding a "ready" flag to the state object that attempts to execute the command along with a queue of spammed commands, but it ends up executing one command and queuing up the rest i.e. each subsequent command executes something that got queued up that should've been executed before. I must be missing something about the timer. private readonly Queue<SpammedCommand> queuedCommands = new Queue<SpammedCommand>(); private bool ready = true; private void TryExecuteCommand(string input) { var commandContext = CommandContext.Create(input); var player = Server.Current.Database.Get<Player>(Session.Player.Key); var commandInfo = Server.Current.CommandLookup .FindCommand(commandContext.CommandName, player.IsAdmin); if (commandInfo != null) { if (!ready) { // queue command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo }); return; } if (queuedCommands.Count > 0) { // queue the incoming command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo, }); // dequeue and execute var command = queuedCommands.Dequeue(); command.Info.Command.Execute(Session, command.Context); setTimeout(command.Info.TickLength); return; } commandInfo.Command.Execute(Session, commandContext); setTimeout(commandInfo.TickLength); } else { Session.WriteLine("Command not recognized"); } } Finally, setTimeout was supposed to set the execution delay (TickLength) for that command, and makeReady just sets the ready flag on the state object to true. private void setTimeout(TickDelay tickDelay) { ready = false; var t = new System.Timers.Timer() { Interval = (long) tickDelay, AutoReset = false, }; t.Elapsed += makeReady; t.Start(); // fire this in tickDelay ms } // MAKE READYYYYY!!!! private void makeReady(object sender, System.Timers.ElapsedEventArgs e) { ready = true; } Am I missing something about the System.Timers.Timer created in setTimeout? How can I execute (and output) spammed commands per TickLength without using Thread.Sleep?

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• Session Diagram &quot;A Way For Better Controlling Your Session&quot;

  An article discussion a solution for cleaning session from unnecessary object in a simple way.

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• APress Deal of the Day - 11/Nov/2011 - Accelerated C# 2010

  - by TATWORTH

  Today's $10 Deal of the day from Apress at http://www.apress.com/9781430225379 is Accelerated C# 2010 "C# 2010 offers powerful new features, and this book is the fastest path to mastering them—and the rest of C#—for both experienced C# programmers moving to C# 2010 and programmers moving to C# from another object-oriented language. " I cannot improve on the description on thew APress web site: "If you're an experienced C# programmer, you need to understand how C# has changed with C# 2010. If you're an experienced object-oriented programmer moving to C#, you want to ramp up quickly in the language while learning the latest features and techniques. In either case, this book is for you. The first three chapters succinctly present C# fundamentals, for those new to or reviewing C#. The rest of the book covers all the major C# features, in great detail, explaining how they work and how best to use them. Whatever your background or need, you’ll treasure this book for as long as you code in C# 2010."   Can't code withoutThe best C# & VB.NET refactoring plugin for Visual Studio

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• Using Instance Nodes, worth it?

  - by Twitch

  I am making a 2d game where there are various environments with lots and lots of objects. There is a forest scene with like 1200 objects in total(trees mainly), of which around 100 are visible on the camera at any given time, as you move through the level. These are comprised of around 20 different kind of trees and other props. Each object is usually 2-6 triangles with a transparent texture. My developer asked me to replace each object in the scene with a node, and keeping only a minimal amount of actual objects which would be 300+ or so(?), since there are a few modified unique meshes. So he can instantiate the actual objects to keep the game light. Is this actually effective? And if so how much? I 've read about draw calls and such and I suppose that if I combine each texture (10 kinds of trees) in 1 mesh it will have the same effect?

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• Is there a name for this use of the State design pattern?

  - by Chris C

  I'm looking to see if there is a particular name for this style of programming a certain kind of behavior into a program. Said program runs in real time, in an update loop, and the program uses the State design pattern to do some work, but it's the specific way it does the work that I want to know about. Here's how it's used. - Object Foo constructed, with concrete StateA object in it - First loop runs --- Foo.Run function calls StateA.Bar --- in StateA.Bar replace Foo's state to StateB - Second loop runs --- Foo.Run calls StateB.Bar - Third loop runs --- Foo.Run calls StateB.Bar - Fourth loop --- etc. So in short, Foo doesn't have an explicit Initialize function. It will just have Run, but Run will do something unique in the first frame to initialize something for Foo and then replace it with a different action that will repeat in all the frames following it- thus not needing to check if Foo's already initialized. It's just a "press start and go" action. What would you call implementing this type of behavior?

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• Is the escaping provided by the Google-Gson library enough to ensure a safe JSON payload?

  - by Lifetime_Learner

  I am currently using the Google-Gson library to convert Java objects into JSON inside a web service. Once the object has been converted to JSON, it is returned to the client to be converted into a JSON object using the JavaScript eval() function. Is the character escaping provided by the Gson library enough to ensure that nothing nasty will happen when I run the eval() function on the JSON payload? Do I need to HTML Encode the Strings in the Java Objects before passing them to the Gson library? Are there any other security concerns that I should be aware of?

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• How can I neatly embed Flash in a page in a way that is cross-browser compatible?

  - by Mark Hatton

  When I receive Flash objects from my designer, it comes with an example HTML page which includes both <object> tags and <embed> tags as well as a whole heap of JavaScript. If I copy and paste this code in to my webpage, it works, but the code looks a mess (and there is so much of it!). If I remove the extra code and try either just <embed> or <object> on their own, it works in some browsers, but not others. Is there a neat, minimal method that works in all the major browsers?

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• Adding a small slide when player releases left/right key

  - by Dave

  the aim is for the player object to slow down and stop instead of just stopping dead. The following codes works ok when the player is not jumping, but gets stuck in an object if the player is in the air when they do it. Left Key released event: if hsp = 0 exit; hspeed = -3; friction = 0.20; if obj_Player.hspeed = 0 { hspeed = 0; } Right key released event: if hsp = 0 exit; hspeed = +3; friction = 0.20; if obj_Player.hspeed = 0 { hspeed = 0; } and here's the horizontal collision code for interest: if (place_meeting(x+hsp,y,obj_bound)) { while(!place_meeting(x+sign(hsp),y,obj_bound)) { x += sign(hsp); } hsp = 0; } x += hsp; Any help would be much appreciated. Thanks.

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• Unintentional run-in with C# thread concurrency

  - by geekrutherford

  For the first time today we began conducting load testing on a ASP.NET application already in production. Obviously you would normally want to load test prior to releasing to a production environment, but that isn't the point here.   We ran a test which simulated 5 users hitting the application doing the same actions simultaneously. The first few pages visited seemed fine and then things just hung for a while before the test failed. While the test was running I was viewing the performance counters on the server noting that the CPU was consistently pegged at 100% until the testing tool gave up.   Fortunately the application logs all exceptions including those unhandled to the database (thanks to log4net). I checked the log and low and behold the error was:   System.ArgumentException: An item with the same key has already been added. (The rest of the stack trace intentionally omitted)   Since the code was running with debug on the line number where the exception occured was also provided. I began inspecting the code and almost immediately it hit me, the section of code responsible for the exception is trying to initialize a static class. My next question was how is this code being hit multiple times when I have a rudimentary check already in place to prevent this kind of thing (i.e. a check on a public variable of the static class before entering the initializing routine). The answer...the check fails because the value is not set before other threads have already made it through.   Not being one who consistently works with threading I wasn't quite sure how to handle this problem. Fortunately a co-worker recalled having to lock a section of code in the past but couldn't recall exactly how. After a quick search on Google the solution is as follows:   Object objLock = new Object(); lock(objLock) { //logic requiring lock }   The lock statement takes an object and tells the .NET runtime that the current thread has exclusive access while the code within brackets is executing. Once the code completes, the lock is released for another thread to utilize.   In my case, I only need to execute the inner code once to initialize my static class. So within the brackets I have a check on a public variable to prevent it from being initialized again.

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• Manual memory allocation and purity

  - by Eonil

  Language like Haskell have concept of purity. In pure function, I can't mutate any state globally. Anyway Haskell fully abstracts memory management, so memory allocation is not a problem here. But if languages can handle memory directly like C++, it's very ambiguous to me. In these languages, memory allocation makes visible mutation. But if I treat making new object as impure action, actually, almost nothing can be pure. So purity concept becomes almost useless. How should I handle purity in languages have memory as visible global object?

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• Should I use the factory design pattern for every class?

  - by Frog

  I've been writing a website in PHP. As the code becomes more complex, I keep finding problems that can be solved using the factory design pattern. For example: I've a got a class Page which has subclasses HTMLPage, XMLPage, etc. Depending on some input I need to return an object of either one of these classes. I use the factory design pattern to do this. But as I encounter this problem in more classes, I keep having to change code which still initiates an object using its constructor. So now I'm wondering: is it a good idea to change all code so that it uses the factory design pattern? Or are there big drawbacks? I'm currently in a position to change this, so your answers would be really helpful.

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• Binding data grid at run time

  In this article you will leatn how to use a IDictionary object.

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• How do I install graphviz 2.29 in 12.04?

  - by bidur

  In my ubuntu 12.04, the graphviz is not the latest version(2.29). I need some features available in the latest version of graphviz. I tried to install the graphviz version 2.29, which requires libgraphviz4(=2.18). I anyhow installed libgraphviz4 and installed graphviz 2.29. For that I have to remove packages libcdt4 and libpathplan4. Now whenever I try to generate graph, I get some problems: For e.g.: dot -Kfdp -n -Tpng -o samplePOS.png forcePOS.dot It says: dot: error while loading shared libraries: libgvc.so.6: cannot open shared object file: No such file or directory neato -Tps -o sample_1.ps sourcedot.gv It says: neato: error while loading shared libraries: libgvc.so.6: cannot open shared object file: No such file or directory So, I am looking for some ways so that I can run graphviz 2.29 in my ubuntu 12.04.

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• Are these non-standard applications of rendering practical in games?

  - by maul

  I've recently got into 3D and I came up with a few different "tricky" rendering techniques. Unfortunately I don't have the time to work on this myself, but I'd like to know if these are known methods and if they can be used in practice. Hybrid rendering Now I know that ray-tracing is still not fast enough for real-time rendering, at least on home computers. I also know that hybrid rendering (a combination of rasterization and ray-tracing) is a well known theory. However I had the following idea: one could separate a scene into "important" and "not important" objects. First you render the "not important" objects using traditional rasterization. In this pass you also render the "important" objects using a special shader that simply marks these parts on the image using a special color, or some stencil/depth buffer trickery. Then in the second pass you read back the results of the first pass and start ray tracing, but only from the pixels that were marked by the "important" object's shader. This would allow you to only ray-trace exactly what you need to. Could this be fast enough for real-time effects? Rendered physics I'm specifically talking about bullet physics - intersection of a very small object (point/bullet) that travels across a straight line with other, relatively slow-moving, fairly constant objects. More specifically: hit detection. My idea is that you could render the scene from the point of view of the gun (or the bullet). Every object in the scene would draw a different color. You only need to render a 1x1 pixel window - the center of the screen (again, from the gun's point of view). Then you simply check that central pixel and the color tells you what you hit. This is pixel-perfect hit detection based on the graphical representation of objects, which is not common in games. Afaik traditional OpenGL "picking" is a similar method. This could be extended in a few ways: For larger (non-bullet) objects you render a larger portion of the screen. If you put a special-colored plane in the middle of the scene (exactly where the bullet will be after the current frame) you get a method that works as the traditional slow-moving iterative physics test as well. You could simulate objects that the bullet can pass through (with decreased velocity) using alpha blending or some similar trick. So are these techniques in use anywhere, and/or are they practical at all?

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• Why circles are not created if small?

  - by Suzan Cioc

  I have changed the scale to my own and now I cant create any object, including circle, if it is of the size which is normal for my scale. I am to create big object first and then modify it to smaller size. Looks like minimal size protection is set somewhere. Where? UPDATE While creating a circle, if I drag for 0.04m circle disappears after drag end. If I drag for 0.08m circle also disappears. If I drag for more than 0.1m, circle persists after drag end. How to set so that it persist after 0.01m too?

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• How to get the Dash and HUD to appear. (and stop Unity spewing error messages.)

  - by Ubuntiac

  I just installed Ubuntu 12.04 on my wifes Dell Inspiron 1501, which uses an R300 ATI graphics chip. Neither the Dash or HUD appear when pushing the appropriate key. When I try unity --reset & in the terminal, I see that over and over it's spitting out: r300: CS space validation failed. (not enough memory?) Skipping rendering. This is just after starting Ubuntu with no apps open, so I find it hard to believe that just rendering the Dash / HUD is completely blowing out the VRAM. Any suggestions on getting this working? /usr/lib/nux/unity_support_test -p shows OpenGL vendor string: X.Org R300 Project OpenGL renderer string: Gallium 0.4 on ATI RS480 OpenGL version string: 2.1 Mesa 8.0.2 Not software rendered: yes Not blacklisted: yes GLX fbconfig: yes GLX texture from pixmap: yes GL npot or rect textures: yes GL vertex program: yes GL fragment program: yes GL vertex buffer object: yes GL framebuffer object: yes GL version is 1.4+: yes Unity 3D supported: yes All sections say "YES"

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• Using static in PHP

  - by nischayn22

  I have a few functions in PHP that read data from functions in a class readUsername(int userId){ $reader = getReader(); return $reader->getname(userId); } readUserAddress(){ $reader = getReader(); return $reader->getaddress(userId); } All these make a call to getReader() { require_once("Reader.php"); static $reader = new Reader(); return $reader; } An overview of Reader class Reader{ getname(int id) { //if in-memory cache exists for this id return that //else get from db and cache it } getaddress(int id) { $this->getname(int id); //get address from name here } /*Other stuff*/ } Why is class Reader needed The Reader class does some in-memory caching of user details. So, I need only one object of class Reader and it will cache the user details instead of making multiple db calls. I am using static so that it the object gets created only once. Is this the right approach or should I do something else?

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• LINQ/LAMBDA filter query by date [on hold]

  - by inquisitive_one

  I'm trying to use LINQ to SQL to retrieve earnings data for a particular date range. Currently the table is set up as follows: Comp Eps Year Quarter IBM .5 2012 2 IBM .65 2012 3 IBM .60 2012 4 IBM .5 2011 2 IBM .7 2013 1 IBM .8 2013 2 Except for Eps, all fields have a data type of string or char. Eps has a data type of double. Here's my code: var myData = myTable .Where(t => t.Comp.Equals("IBM") && Convert.Int32(string.Format("{0}{1}", t.Year, t.Quarter)) <= 20131); I get the following error when I tried that code: Method 'System.String Format(System.String, System.Object, System.Object)' has no supported translation to SQL How can I select all Eps that has a year & quarter less than "20132" using a lambda expression?

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• Is it appropriate to try to control the order of finalization?

  - by Strilanc

  I'm writing a class which is roughly analogous to a CancellationToken, except it has a third state for "never going to be cancelled". At the moment I'm trying to decide what to do if the 'source' of the token is garbage collected without ever being set. It seems that, intuitively, the source should transition the associated token to the 'never cancelled' state when it is about to be collected. However, this could trigger callbacks who were only kept alive by their linkage from the token. That means what those callbacks reference might now in the process of finalization. Calling them would be bad. In order to "fix" this, I wrote this class: public sealed class GCRoot { private static readonly GCRoot MainRoot = new GCRoot(); private GCRoot _next; private GCRoot _prev; private object _value; private GCRoot() { this._next = this._prev = this; } private GCRoot(GCRoot prev, object value) { this._value = value; this._prev = prev; this._next = prev._next; _prev._next = this; _next._prev = this; } public static GCRoot Root(object value) { return new GCRoot(MainRoot, value); } public void Unroot() { lock (MainRoot) { _next._prev = _prev; _prev._next = _next; this._next = this._prev = this; } } } intending to use it like this: Source() { ... _root = GCRoot.Root(callbacks); } void TransitionToNeverCancelled() { _root.Unlink(); ... } ~Source() { TransitionToNeverCancelled(); } but now I'm troubled. This seems to open the possibility for memory leaks, without actually fixing all cases of sources in limbo. Like, if a source is closed over in one of its own callbacks, then it is rooted by the callback root and so can never be collected. Presumably I should just let my sources be collected without a peep. Or maybe not? Is it ever appropriate to try to control the order of finalization, or is it a giant warning sign?

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• Using COM objects in scripting languages -- Part 2 (Python)

  Article shows how to instantiate a COM object in Python and use its methods and properties.

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• XNA Monogame GameState Management not deserilaizing

  - by Pectus Excavatum

  I am having some trouble serializing/deserializing in a little game I am doing to teach myself monogame. Basically, I am using the gamestatemnanagement resources common to monogame (screen manager etc). Then I am serializing my screen manager component and all associated screens in the OnDeactivated method: protected override void OnDeactivated(Object sender, EventArgs args) { foreach (GameplayScreen screen in mScreenManager.GetScreens()) { DataManager.SaveData(screen.Level.LevelData); } mScreenManager.SerializeState(); } The Save data bit is to do with something else. Then I then override OnActivated to de serialize protected override void OnActivated(Object sender, EventArgs args) { //System.Diagnostics.Debug.WriteLine("here activating"); mScreenManager.DeserializeState(); } However, when this runs it just loads a blank screen - it goes into the game initialize and the game draw method, but doesnt go down into the screens initialize or draw methods. I have no idea why this might be - any help would be greatly appreciated. I am not the only one who has encountered this - I found this post also - https://monogame.codeplex.com/discussions/391117

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• Should iOS games use a Timer?

  - by ????

  No matter what frameworks we use -- Core Graphics, Cocos2D, OpenGL ES -- to write games, should a timer be used (for games that has animation even when a user doesn't do any input, such as after firing a missile and waiting to see if the UFO is hit)? I read that NSTimer might not get fired until after scheduled time (interval), and CADisplayLink can delay and get fired at a later time as well, only that it tells you how late it is so you can move the object more, so it can make the object look like it skipped frame. Must we use a Timer? And if so, what is the best one to use?

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• Assigning a colour to imorted obj. files that are being used as default material

  - by Salino

  I am having a problem with assigning a colour to the different meshes that I have on one object. The technique that I have used is the first approach on this site. Is it possible to export a simulation (animation) from Blender to Unity? So what I would like to do is the following. I have about 107 meshes that are different frames from my shape key animation of my blender model. What I would like to have is that the first mesh will be bright green and up to the 40th mesh the colour turns to be white /greyish... the best would be if I could assign every mesh by hand a colour, however they are all default materials. And if I assign the object a colour, the whole "animation" is going to be in that colour

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