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• Segmentation fault while switching QCompleter for QLineEdit [on hold]

  - by san

  I have a QLineEdit that uses autocompletion one which on focusIn event in which it shows paths from XML List(here I have used hardcoded list) but if user doesn't find the path from that list popped by QCompleter than I want user to be able to browse to path typing '/' in QLineEdit , I am not able to select the paths say /Users etc and on trying to type Segmentation fault occurs. from PyQt4.Qt import Qt, QObject,QLineEdit from PyQt4.QtCore import pyqtSlot,SIGNAL,SLOT from PyQt4 import QtGui, QtCore import sys class DirLineEdit(QLineEdit, QtCore.QObject): """docstring for DirLineEdit""" def __init__(self): super(DirLineEdit, self).__init__() self.defaultList = ['~/Development/python/searchMethod', '~/Development/Nuke_python', '~/Development/python/openexr', '~/Development/python/cpp2python'] self.textChanged.connect(self.__dirCompleter) def focusInEvent(self, event): if len(self.text()) == 0: self._pathsList() QtGui.QLineEdit.focusInEvent(self, event) self.completer().complete() def __dirCompleter(self): if len(self.text()) == 0: model = MyListModel(self.defaultList, self) completer = QtGui.QCompleter(model, self) completer.setModel(model) else: dirModel = QtGui.QFileSystemModel() dirModel.setRootPath(QtCore.QDir.currentPath()) dirModel.setFilter(QtCore.QDir.AllDirs | QtCore.QDir.NoDotAndDotDot | QtCore.QDir.Files) dirModel.setNameFilterDisables(0) completer = QtGui.QCompleter(dirModel, self) completer.setCaseSensitivity(QtCore.Qt.CaseInsensitive) completer.setModel(dirModel) self.setCompleter(completer) def _pathsList(self): completerList = QtCore.QStringList() for i in self.defaultList: completerList.append(QtCore.QString(i)) lineEditCompleter = QtGui.QCompleter(completerList) lineEditCompleter.setCompletionMode(QtGui.QCompleter.UnfilteredPopupCompletion) self.setCompleter(lineEditCompleter) class MyListModel(QtCore.QAbstractListModel): def __init__(self, datain, parent=None, *args): """ datain: a list where each item is a row """ QtCore.QAbstractTableModel.__init__(self, parent, *args) self.listdata = datain def rowCount(self, parent=QtCore.QModelIndex()): return len(self.listdata) def data(self, index, role): if index.isValid() and role == QtCore.Qt.DisplayRole: return QtCore.QVariant(self.listdata[index.row()]) else: return QtCore.QVariant() app = QtGui.QApplication(sys.argv) smObj = DirLineEdit() smObj.show() app.exec_() Please help fix this or suggest better way of implementation?

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• Generic Repositories with DI & Data Intensive Controllers

  - by James

  Usually, I consider a large number of parameters as an alarm bell that there may be a design problem somewhere. I am using a Generic Repository for an ASP.NET application and have a Controller with a growing number of parameters. public class GenericRepository<T> : IRepository<T> where T : class { protected DbContext Context { get; set; } protected DbSet<T> DbSet { get; set; } public GenericRepository(DbContext context) { Context = context; DbSet = context.Set<T>(); } ...//methods excluded to keep the question readable } I am using a DI container to pass in the DbContext to the generic repository. So far, this has met my needs and there are no other concrete implmentations of IRepository<T>. However, I had to create a dashboard which uses data from many Entities. There was also a form containing a couple of dropdown lists. Now using the generic repository this makes the parameter requirments grow quickly. The Controller will end up being something like public HomeController(IRepository<EntityOne> entityOneRepository, IRepository<EntityTwo> entityTwoRepository, IRepository<EntityThree> entityThreeRepository, IRepository<EntityFour> entityFourRepository, ILogError logError, ICurrentUser currentUser) { } It has about 6 IRepositories plus a few others to include the required data and the dropdown list options. In my mind this is too many parameters. From a performance point of view, there is only 1 DBContext per request and the DI container will serve the same DbContext to all of the Repositories. From a code standards/readability point of view it's ugly. Is there a better way to handle this situation? Its a real world project with real world time constraints so I will not dwell on it too long, but from a learning perspective it would be good to see how such situations are handled by others.

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• Is there a name for the Builder Pattern where the Builder is implemented via interfaces so certain parameters are required?

  - by Zipper

  So we implemented the builder pattern for most of our domain to help in understandability of what actually being passed to a constructor, and for the normal advantages that a builder gives. The one twist was that we exposed the builder through interfaces so we could chain required functions and unrequired functions to make sure that the correct parameters were passed. I was curious if there was an existing pattern like this. Example below: public class Foo { private int someThing; private int someThing2; private DateTime someThing3; private Foo(Builder builder) { this.someThing = builder.someThing; this.someThing2 = builder.someThing2; this.someThing3 = builder.someThing3; } public static RequiredSomething getBuilder() { return new Builder(); } public interface RequiredSomething { public RequiredDateTime withSomething (int value); } public interface RequiredDateTime { public OptionalParamters withDateTime (DateTime value); } public interface OptionalParamters { public OptionalParamters withSeomthing2 (int value); public Foo Build ();} public static class Builder implements RequiredSomething, RequiredDateTime, OptionalParamters { private int someThing; private int someThing2; private DateTime someThing3; public RequiredDateTime withSomething (int value) {someThing = value; return this;} public OptionalParamters withDateTime (int value) {someThing = value; return this;} public OptionalParamters withSeomthing2 (int value) {someThing = value; return this;} public Foo build(){return new Foo(this);} } } Example of how it's called: Foo foo = Foo.getBuilder().withSomething(1).withDateTime(DateTime.now()).build(); Foo foo2 = Foo.getBuilder().withSomething(1).withDateTime(DateTime.now()).withSomething2(3).build();

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• Understanding math used to determine if vector is clockwise / counterclockwise from your vector

  - by MTLPhil

  I'm reading Programming Game AI by Example by Mat Buckland. In the Math & Physics primer chapter there's a listing of the declaration of a class used to represent 2D vectors. This class contains a method called Sign. It's implementation is as follows //------------------------ Sign ------------------------------------------ // // returns positive if v2 is clockwise of this vector, // minus if anticlockwise (Y axis pointing down, X axis to right) //------------------------------------------------------------------------ enum {clockwise = 1, anticlockwise = -1}; inline int Vector2D::Sign(const Vector2D& v2)const { if (y*v2.x > x*v2.y) { return anticlockwise; } else { return clockwise; } } Can someone explain the vector rules that make this hold true? What do the values of y*v2.x and x*v2.y that are being compared actually represent? I'd like to have a solid understanding of why this works rather than just accepting that it does without figuring it out. I feel like it's something really obvious that I'm just not catching on to. Thanks for your help.

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• Learn More About the Scalability, Uptime, and Agility of MySQL Cluster

  - by Antoinette O'Sullivan

  Learn more about the uncompromising scalability, uptime, and agility of MySQL Cluster by taking the authentic MySQL Cluster training course. During this three day class, you will learn how to properly configure and manage the cluster nodes to ensure high availability, how to install the different nodes as well as get a better understanding of the internals of the cluster. Events currently on the schedule for this class include:  Location  Date  Delivery Language  Wein, Austria  4 February 2013  German London, England  12 June 2013   English  Rennes, France 26 February 2013   French  Hamburg, Germany 21 January 2013   German  Munich, Germany  10 June 2013 German   Stuttgart, Germany  26 March 2013  German  Budapest, Hungary  19 June 2013  Hungarian  Milan, Italy  4 February 2013  Italy  Warsaw, Poland  18 March 2013  Polish  Barcelona, Spain  4 March 2013  Spanish  Madrid, Spain 25 February 2013   Spanish Chicago, United States  27 March 2013   English  Reston, United States  6 February 2013  English  Jakarta, Indonesia 21 January 2013  English   Singapore 18 February 2013   English To register for an event or to see further details on this or other courses in the authentic MySQL curriculum, please go to http://oracle.com/education/mysql.

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• Object oriented EDI handling in PHP

  - by Robert van der Linde

  I'm currently starting a new sub project where I will: Retrieve the order information from our mainframe Save the order information to our web-apps' database Send the order as EDI (either D01b or D93a) Receive the order response, despatch advice and invoice messages Do all kinds of fun things with the resulting datasets. However I am struggling with my initial class designs. The order information will be retrieved from the mainframe which will result in a "AOrder" class, this isn't a problem, I am not sure about how to mold this local object into an EDI string. Should I create EDIOrder/EDIOrderResponse/etc classes with matching decorators (EDIOrderD01BDecorator, EDIOrderD93ADecorator)? Do I need builder objects or can I do: // $myOrder is instance of AOrder $myOrder->toEDIOrder(); $decorator = new EDIOrderD01BDecorator($myOrder); $edi = $decorator->getEDIString(); And it'll have to work the other way around as well. Is the following code a good way of handling this problem or should I go about this differently? $ediString = $myEDIMessageBroker->fetch(); $ediOrderResponse = EDIOrderResponse::fromString($ediString); I'm just not so sure about how I should go about designing the classes and interactions between them. Thanks for reading and helping.

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• Use CompiledQuery.Compile to improve LINQ to SQL performance

  - by Michael Freidgeim

  After reading DLinq (Linq to SQL) Performance and in particular Part 4  I had a few questions. If CompiledQuery.Compile gives so much benefits, why not to do it for all Linq To Sql queries? Is any essential disadvantages of compiling all select queries? What are conditions, when compiling makes whose performance, for how much percentage? World be good to have default on application config level or on DBML level to specify are all select queries to be compiled? And the same questions about Entity Framework CompiledQuery Class. However in comments I’ve found answer  of the author ricom 6 Jul 2007 3:08 AM Compiling the query makes it durable. There is no need for this, nor is there any desire, unless you intend to run that same query many times. SQL provides regular select statements, prepared select statements, and stored procedures for a reason.  Linq now has analogs. Also from 10 Tips to Improve your LINQ to SQL Application Performance   If you are using CompiledQuery make sure that you are using it more than once as it is more costly than normal querying for the first time. The resulting function coming as a CompiledQuery is an object, having the SQL statement and the delegate to apply it.  And your delegate has the ability to replace the variables (or parameters) in the resulting query. However I feel that many developers are not informed enough about benefits of Compile. I think that tools like FxCop and Resharper should check the queries  and suggest if compiling is recommended. Related Articles for LINQ to SQL: MSDN How to: Store and Reuse Queries (LINQ to SQL) 10 Tips to Improve your LINQ to SQL Application Performance Related Articles for Entity Framework: MSDN: CompiledQuery Class Exploring the Performance of the ADO.NET Entity Framework - Part 1 Exploring the Performance of the ADO.NET Entity Framework – Part 2 ADO.NET Entity Framework 4.0: Making it fast through Compiled Query

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• Why the R# Method Group Refactoring is Evil

  - by Liam McLennan

  The refactoring I’m talking about is recommended by resharper when it sees a lambda that consists entirely of a method call that is passed the object that is the parameter to the lambda. Here is an example: public class IWishIWasAScriptingLanguage { public void SoIWouldntNeedAllThisJunk() { (new List<int> {1, 2, 3, 4}).Select(n => IsEven(n)); } private bool IsEven(int number) { return number%2 == 0; } } When resharper gets to n => IsEven(n) it underlines the lambda with a green squiggly telling me that the code can be replaced with a method group. If I apply the refactoring the code becomes: public class IWishIWasAScriptingLanguage { public void SoIWouldntNeedAllThisJunk() { (new List<int> {1, 2, 3, 4}).Select(IsEven); } private bool IsEven(int number) { return number%2 == 0; } } The method group syntax implies that the lambda’s parameter is the same as the IsEven method’s parameter. So a readable, explicit syntax has been replaced with an obfuscated, implicit syntax. That is why the method group refactoring is evil.

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• How to do Cross Platform in own Engine? [on hold]

  - by Mineorbit

  At the Moment I finished the first game with my game engine(if I wanna call it like that) which is based in LWJGL. Now i'm worring if I could do crossplattforming in my engine. I build me a tool tool with a batch file to compile my project dir into an .exe . At first i'm looking to do it on Android with an comparable batch file. An link for an tutorial would be awesome! At next place there would be an renderer and audiosystem. If read that theres an OpenGL ES renderer, and I allready played a bit around with the Android SDK. But I use the Texture and Audio class in slick-util. So I thought about creating OOP classes that carry around the data and load it in an platform specific Buffer. A Link for an equaly easy-to-use Texture or Audio class would be awesome! Thats all for now! Answers would be awesome! Thanks, Mineorbit!

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• Ways to organize interface and implementation in C++

  - by Felix Dombek

  I've seen that there are several different paradigms in C++ concerning what goes into the header file and what to the cpp file. AFAIK, most people, especially those from a C background, do: foo.h class foo { private: int mem; int bar(); public: foo(); foo(const foo&); foo& operator=(foo); ~foo(); } foo.cpp #include foo.h foo::bar() { return mem; } foo::foo() { mem = 42; } foo::foo(const foo& f) { mem = f.mem; } foo::operator=(foo f) { mem = f.mem; } foo::~foo() {} int main(int argc, char *argv[]) { foo f; } However, my lecturers usually teach C++ to beginners like this: foo.h class foo { private: int mem; int bar() { return mem; } public: foo() { mem = 42; } foo(const foo& f) { mem = f.mem; } foo& operator=(foo f) { mem = f.mem; } ~foo() {} } foo.cpp #include foo.h int main(int argc, char* argv[]) { foo f; } // other global helper functions, DLL exports, and whatnot Originally coming from Java, I have also always stuck to this second way for several reasons, such as that I only have to change something in one place if the interface or method names change, that I like the different indentation of things in classes when I look at their implementation, and that I find names more readable as foo compared to foo::foo. I want to collect pro's and con's for either way. Maybe there are even still other ways? One disadvantage of my way is of course the need for occasional forward declarations.

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• Using PreApplicationStartMethod for ASP.NET 4.0 Application to Initialize assemblies

  - by ChrisD

  Sometimes your ASP.NET application needs to hook up some code before even the Application is started. Assemblies supports a custom attribute called PreApplicationStartMethod which can be applied to any assembly that should be loaded to your ASP.NET application, and the ASP.NET engine will call the method you specify within it before actually running any of code defined in the application. Lets discuss how to use it using Steps : 1. Add an assembly to an application and add this custom attribute to the AssemblyInfo.cs. Remember, the method you speicify for initialize should be public static void method without any argument. Lets define a method Initialize. You need to write : [assembly:PreApplicationStartMethod(typeof(MyInitializer.InitializeType), "InitializeApp")] 2. After you define this to an assembly you need to add some code inside InitializeType.InitializeApp method within the assembly. public static class InitializeType {     public static void InitializeApp()     {           // Initialize application     } } 3. You must reference this class library so that when the application starts and ASP.NET starts loading the dependent assemblies, it will call the method InitializeApp automatically. Warning Even though you can use this attribute easily, you should be aware that you can define these kind of method in all of your assemblies that you reference, but there is no guarantee in what order each of the method to be called. Hence it is recommended to define this method to be isolated and without side effect of other dependent assemblies. The method InitializeApp will be called way before the Application_start event or even before the App_code is compiled. This attribute is mainly used to write code for registering assemblies or build providers. Read Documentation I hope this post would come helpful.

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• Nested entities in Google App Engine. Do I do it right?

  - by Aleksandr Makov

  Trying to make most of the GAE Datastore entities concept, but some doubts drill my head. Say I have the model: class User(ndb.Model): email = ndb.StringProperty(indexed=True) password = ndb.StringProperty(indexed=False) first_name = ndb.StringProperty(indexed=False) last_name = ndb.StringProperty(indexed=False) created_at = ndb.DateTimeProperty(auto_now_add=True) @classmethod def key(cls, email): return ndb.Key(User, email) @classmethod def Add(cls, email, password, first_name, last_name): user = User(parent=cls.key(email), email=email, password=password, first_name=first_name, last_name=last_name) user.put() UserLogin.Record(email) class UserLogin(ndb.Model): time = ndb.DateTimeProperty(auto_now_add=True) @classmethod def Record(cls, user_email): login = UserLogin(parent=User.key(user_email)) login.put() And I need to keep track of times of successful login operations. Each time user logs in, an UserLogin.Record() method will be executed. Now the question — do I make it right? Thanks. EDIT 2 Ok, used the typed arguments, but then it raised this: Expected Key instance, got User(key=Key('User', 5418393301680128), created_at=datetime.datetime(2013, 6, 27, 10, 12, 25, 479928), email=u'[email protected]', first_name=u'First', last_name=u'Last', password=u'password'). It's clear to understand, but I don't get why the docs are misleading? They implicitly propose to use: # Set Employee as Address entity's parent directly... address = Address(parent=employee) But Model expects key. And what's worse the parent=user.key() swears that key() isn't callable. And I found out the user.key works. EDIT 1 After reading the example form the docs and trying to replicate it — I got type error: TypeError('Model constructor takes no positional arguments.'). This is the exacto code used: user = User('[email protected]', 'password', 'First', 'Last') user.put() stamp = UserLogin(parent=user) stamp.put() I understand that Model was given the wrong argument, BUT why it's in the docs?

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• Is there a precedent for the license on a compiler restricting the kind of development you can use it for?

  - by Jim McKeeth

  It was recently let slip that the new EULA for Delphi XE3 will prohibit Client Server development with the Professional edition without the additional purchase of a Client Server license pack. This is not to say the Professional version will lack the features, but the license will specifically prohibit the developer from using the compiler for a specific class of development, even with 3rd party or home grown solutions. So my question is if there is a precedent of a compiler or similar creative tool prohibiting the class of work you can use it for. Specifically a commercially licensed "professional" tool like Delphi XE3. Also, would such a restriction be legally enforceable? I know there have been educational edition or starter edition tools in the past that have restricted their use for commercial purposes, but those were not sold as "professional" tools. Also I know that a lot of computing software and equipment will have a disclaimer that it is not for use in "life support equipment" or "nuclear power" but that is more of avoiding liability than prohibiting activity. Seems like I recall Microsoft putting a restriction in FrontPage that you couldn't use it to create a web site that reflected poorly on Microsoft, but they pulled that restriction before it could be tested legally.

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• Why to say, my function is of IFly type rather than saying it's Airplane type

  - by Vishwas Gagrani

  Say, I have two classes: Airplane and Bird, both of them fly. Both implement the interface IFly. IFly declares a function StartFlying(). Thus both Airplane and Bird have to define the function, and use it as per their requirement. Now when I make a manual for class reference, what should I write for the function StartFlying? 1) StartFlying is a function of type IFly . 2) StartFlying is a function of type Airplane 3) StartFlying is a function of type Bird. My opinion is 2 and 3 are more informative. But what i see is that class references use the 1st one. They say what interface the function is declared in. Problem is, I really don't get any usable information from knowing StartFlying is IFly type. However, knowing that StartFlying is a function inside Airplane and Bird, is more informative, as I can decide which instance (Airplane or Bird ) to use. Any lights on this: how saying StartFlying is a function of type IFly, can help a programmer understanding how to use the function?

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• Implementing a ILogger interface to log data

  - by Jon

  I have a need to write data to file in one of my classes. Obviously I will pass an interface into my class to decouple it. I was thinking this interface will be used for testing and also in other projects. This is my interface: //This could be used by filesystem, webservice public interface ILogger { List<string> PreviousLogRecords {get;set;} void Log(string Data); } public interface IFileLogger : ILogger { string FilePath; bool ValidFileName; } public class MyClassUnderTest { public MyClassUnderTest(IFileLogger logger) {....} } [Test] public void TestLogger() { var mock = new Mock<IFileLogger>(); mock.Setup(x => x.Log(Is.Any<string>).AddsDataToList()); //Is this possible?? var myClass = new MyClassUnderTest(mock.Object); myClass.DoSomethingThatWillSplitThisAndLog3Times("1,2,3"); Assert.AreEqual(3,mock.PreviousLogRecords.Count); } This won't work I don't believe as nothing is storing the items so is this possible using Moq and also what do you think of the design of the interface?

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• Strange and erratic transformations when using OpenGL VBOs to render scene

  - by janoside

  I have an existing iOS game with fairly simple scenes (all textured quads) and I'm using Apple's "Texture2D" class. I'm trying to convert this class to use VBOs since the vertices of my objects basically never change so I may as well not re-create them for every object every frame. I have the scene rendering using VBOs but the sizes and orientations of all rendered objects are strange and erratic - though locations seem generally correct. I've been toying with this code for a few days now, and I've found something odd: if I re-create all of my VBOs each frame, everything looks correct, even though I'm almost certain my vertices are not changing. Other notes I'm basing my work on this tutorial, and therefore am also using "IBOs" I create my buffers before rendering begins My buffers include vertex and texture data I'm using OpenGL ES 1.1 Fearing some strange effect of the current matrix GL state at the time of buffer creation I've also tried wrapping my buffer-setup code in a "pushMatrix-loadIdentity-popMatrix" block which (as expected) had no effect I'm aware that various articles have been published demonstrating that VBOs may not help performance, but I want to understand this problem and at least have the option to use them. I realize this is a shot in the dark, but has anyone else experienced this type of strange behavior? What might I be doing to result in this behavior? It's rather difficult for me to isolate the problem since I'm working in an existing, moderately complex project, so suggestions about how to approach the problem are also quite welcome.

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• Hijacking ASP.NET Sessions

  - by Ricardo Peres

  So, you want to be able to access other user’s session state from the session id, right? Well, I don’t know if you should, but you definitely can do that! Here is an extension method for that purpose. It uses a bit of reflection, which means, it may not work with future versions of .NET (I tested it with .NET 4.0/4.5). 1: public static class HttpApplicationExtensions 2: { 3: private static readonly FieldInfo storeField = typeof(SessionStateModule).GetField("_store", BindingFlags.NonPublic | BindingFlags.Instance); 4:  5: public static ISessionStateItemCollection GetSessionById(this HttpApplication app, String sessionId) 6: { 7: var module = app.Modules["Session"] as SessionStateModule; 8:  9: if (module == null) 10: { 11: return (null); 12: } 13:  14: var provider = storeField.GetValue(module) as SessionStateStoreProviderBase; 15:  16: if (provider == null) 17: { 18: return (null); 19: } 20:  21: Boolean locked; 22: TimeSpan lockAge; 23: Object lockId; 24: SessionStateActions actions; 25:  26: var data = provider.GetItem(HttpContext.Current, sessionId.Trim(), out locked, out lockAge, out lockId, out actions); 27:  28: if (data == null) 29: { 30: return (null); 31: } 32:  33: return (data.Items); 34: } 35: } As you can see, it extends the HttpApplication class, that is because we need to access the modules collection, for the Session module. Use with care!

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• Why do memory-managed languages retain the `new` keyword?

  - by Channel72

  The new keyword in languages like Java, Javascript, and C# creates a new instance of a class. This syntax seems to have been inherited from C++, where new is used specifically to allocate a new instance of a class on the heap, and return a pointer to the new instance. In C++, this is not the only way to construct an object. You can also construct an object on the stack, without using new - and in fact, this way of constructing objects is much more common in C++. So, coming from a C++ background, the new keyword in languages like Java, Javascript, and C# seemed natural and obvious to me. Then I started to learn Python, which doesn't have the new keyword. In Python, an instance is constructed simply by calling the constructor, like: f = Foo() At first, this seemed a bit off to me, until it occurred to me that there's no reason for Python to have new, because everything is an object so there's no need to disambiguate between various constructor syntaxes. But then I thought - what's really the point of new in Java? Why should we say Object o = new Object();? Why not just Object o = Object();? In C++ there's definitely a need for new, since we need to distinguish between allocating on the heap and allocating on the stack, but in Java all objects are constructed on the heap, so why even have the new keyword? The same question could be asked for Javascript. In C#, which I'm much less familiar with, I think new may have some purpose in terms of distinguishing between object types and value types, but I'm not sure. Regardless, it seems to me that many languages which came after C++ simply "inherited" the new keyword - without really needing it. It's almost like a vestigial keyword. We don't seem to need it for any reason, and yet it's there. Question: Am I correct about this? Or is there some compelling reason that new needs to be in C++-inspired memory-managed languages like Java, Javascript and C#?

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• Android: how do I switch between game scenes in a game? Any tutorials?

  - by Flavio

  I am trying to create a simple game using the Android SDK without using AndEngine (or any other game engine). I have plenty of experience designing games from the past, but I'm having lots of trouble trying to use the Android SDK to make my game. By far my biggest hurdle right now is switching between views. That is, for example, going from the menu to the first level, etc. I am using a traditional model I learned (I think it's called a scene stack or something?) in which you push the current scene onto a stack and the game's main loop runs the top item of the stack. This model seems non-trivial to implement in the Android SDK, mostly because Android seems to be picky about which thread instantiates which view. My issue is that I want the first level to show up when you press a button on the main menu, but when I instantiate the first level (the level class extends SurfaceView and implements SurfaceHolder.Callback) I get a runtime error complaining that the thread that runs the main menu can't instantiate this class. Something about calling Looper.prepare(). I figured at this point I was probably doing things wrong. I'm not sure how to specifically phrase my issue into a question, so maybe I should leave it as either 1) Does anybody know a good way (or the 'proper' way) to switch between scenes in an Android game? or 2) Are there any tutorials out there which show how to create a game that doesn't take place entirely in one scene? (I have googled for a while to no avail... maybe someone else knows of one?) Thanks!

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• Take care to unhook Anonymous Delegates

  - by David Vallens

  Anonymous delegates are great, they elimiante the need for lots of small classes that just pass values around, however care needs to be taken when using them, as they are not automatically unhooked when the function you created them in returns. In fact after it returns there is no way to unhook them. Consider the following code.   using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Diagnostics; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { SimpleEventSource t = new SimpleEventSource(); t.FireEvent(); FunctionWithAnonymousDelegate(t); t.FireEvent(); } private static void FunctionWithAnonymousDelegate(SimpleEventSource t) { t.MyEvent += delegate(object sender, EventArgs args) { Debug.WriteLine("Anonymous delegate called"); }; t.FireEvent(); } } public class SimpleEventSource { public event EventHandler MyEvent; public void FireEvent() { if (MyEvent == null) { Debug.WriteLine("Attempting to fire event - but no ones listening"); } else { Debug.WriteLine("Firing event"); MyEvent(this, EventArgs.Empty); } } } } If you expected the anonymous delegates do die with the function that created it then you would expect the output Attempting to fire event - but no ones listeningFiring eventAnonymous delegate calledAttempting to fire event - but no ones listening However what you actually get is Attempting to fire event - but no ones listeningFiring eventAnonymous delegate calledFiring eventAnonymous delegate called In my example the issue is just slowing things down, but if your delegate modifies objects, then you could end up with dificult to diagnose bugs. A solution to this problem is to unhook the delegate within the function var myDelegate = delegate(){Console.WriteLine("I did it!");}; MyEvent += myDelegate; // .... later MyEvent -= myDelegate;

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• What conventions or frameworks exist for MVVM in Perl?

  - by Will Sheppard

  We're using Catalyst to render lots of webforms in what will become a large application. I don't like the way all the form data is confusingly into a big hash in the Controller, before being passed to the template. It seems jumbled up and messy for the template. I'm sure there are real disadvantages that I haven't described properly... Are there? One solution is to just decide on a convention for the hash, e.g.: { defaults => { type => ['a', 'b', 'c'] }, input => { type => 'a' }, output => { message => "2 widgets found of type a", widgets => [ 'foo', 'bar' ] } } Another way is to store the page/form data as attributes in a class (a ViewModel?), and pass a whole object to the template, which it could use like this: <p class="message">[% model.message %]<p> [% FOREACH widget IN model.widgets %] Which way is more flexible for large applications? Are there any other solutions or existing Catalyst-compatible frameworks?

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• How do you structure your shared code so that it is "re-findable" for new developers?

  - by awmckinley

  I started working at my current job about 8 months ago, and its been one of the best experiences I've had as a young programmer. It's a small company, and both my co-developers are brilliant guys. One of the practices that they both have been encouraging is lots of code-reuse. Our code base is mainly C#, and we're using a centralized revision control system. The way the repository is currently structured, there is a single folder in which all shared class libraries are placed (along with unit tests for each library), and our revision control system allows for sharing or linking those libraries out to other projects. What I'm trying to understand at this point is how the current structure of the folder can be made more conducive for finding those libraries again. I've talked to the other developers about this, and they agree that it's gotten a little messy. I find that I am sometimes "reinventing the wheel" because I didn't realize that there was an existing piece of code that solved a particular problem. The issue is complicated further by the fact that we're sharing some code between ASP.NET MVC2, WinForms, and Windows CE projects, and sharing code between applications built against multiple versions of .NET. How do other people approach this? Is the answer in naming the libraries in a certain way or is it preferable to invest in some code-search software? Is the answer in doc comments? Should we be sharing libraries at all or should we simply branch the class libraries for re-use? Thanks for any and all help!

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• so, my Cassandra consultant left me and now I'm thinking about reverting to mysql

  - by sathia

  I run a middle size community and some time ago I started to develop social capabilities such as follow, status update, wall etc. For some reason i thought that Cassandra was the right tool for the job so I looked online for a Cassandra developer and I found a very talented one. Unluckily in the midst of the development the dev left (too much jobs) and so I'm here with a very nice class, a very nice demo, but a lot of fears that I won't be able to handle basic things such as compaction, scaling etc. My biggest fear is to go online with all this coolness and then having a site inaccessible for hours or days. The mysql consultant (very talented too) keeps saying me that I should stick with Mysql which I know rather well and in case something's wrong we can manage. In that case I should take the class made for cassandra and abstract it for Mysql. My question is this: Should I find another dev/consultant and stick with Cassandra because for social things it is definitely the best tool for the job, or should I listen to the Mysql consultant and revert to Mysql? About 15k login each day Average 20 actions per user Avg 6 followers x user (These are current statistics, but of course I'd like to increase them as much as possible.)

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• What is meant by, "A user shouldn't decide whether it is an Admin or not. The Privileges or Security system should."

  - by GlenPeterson

  The example used in the question pass bare minimum data to a function touches on the best way to determine whether the user is an administrator or not. One common answer was: user.isAdmin() This prompted a comment which was repeated several times and up-voted many times: A user shouldn't decide whether it is an Admin or not. The Privileges or Security system should. Something being tightly coupled to a class doesn't mean it is a good idea to make it part of that class. I replied, The user isn't deciding anything. The User object/table stores data about each user. Actual users don't get to change everything about themselves. But this was not productive. Clearly there is an underlying difference of perspective which is making communication difficult. Can someone explain to me why user.isAdmin() is bad, and paint a brief sketch of what it looks like done "right"? Really, I fail to see the advantage of separating security from the system that it protects. Any security text will say that security needs to be designed into a system from the beginning and considered at every stage of development, deployment, maintenance, and even end-of-life. It is not something that can be bolted on the side. But 17 up-votes so far on this comment says that I'm missing something important.

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• What is wrong with my game loop/mechanic?

  - by elias94xx

  I'm currently working on a 2d sidescrolling game prototype in HTML5 canvas. My implementations so far include a sprite, vector, loop and ticker class/object. Which can be viewed here: http://elias-schuett.de/apps/_experiments/2d_ssg/js/ So my game essentially works well on todays lowspec PC's and laptops. But it does not on an older win xp machine I own and on my Android 2.3 device. I tend to get ~10 FPS with these devices which results in a too high delta value, which than automaticly gets fixed to 1.0 which results in a slow loop. Now I know for a fact that there is a way to implement a super smooth 60 or 30 FPS loop on both devices. Best example would be: http://playbiolab.com/ I don't need all the chunk and debugging technology impact.js offers. I could even write a super simple game where you just control a damn square and it still wouldn't run on a equally fast 30 or 60 fps. Here is the Loop class/object I'm using. It requires a requestAnimationFrame unify function. Both devices I've tested my game on support requestAnimationFrame, so there is no interval fallback. var Loop = function(callback) { this.fps = null; this.delta = 1; this.lastTime = +new Date; this.callback = callback; this.request = null; }; Loop.prototype.start = function() { var _this = this; this.request = requestAnimationFrame(function(now) { _this.start(); _this.delta = (now - _this.lastTime); _this.fps = 1000/_this.delta; _this.delta = _this.delta / (1000/60) > 2 ? 1 : _this.delta / (1000/60); _this.lastTime = now; _this.callback(); }); }; Loop.prototype.stop = function() { cancelAnimationFrame(this.request); };

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