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• Why is F# member not found when used in subclass

  - by James Black

  I have a base type that I want to inherit from, for all my DAO objects, but this member gets the error further down about not being defined: type BaseDAO() = member v.ExecNonQuery2(conn)(sqlStr) = let comm = new MySqlCommand(sqlStr, conn, CommandTimeout = 10) comm.ExecuteNonQuery |> ignore comm.Dispose |> ignore I inherit in this type: type CreateDatabase() = inherit BaseDAO() member private self.createDatabase(conn) = self.ExecNonQuery2 conn "DROP DATABASE IF EXISTS restaurant" This is what I see when my script runs in the interactive shell: --> Referenced 'C:\Program Files\MySQL\MySQL Connector Net 6.2.3\Assemblies\MySql.Data.dll' [Loading C:\Users\jblack\Documents\Visual Studio 2010\Projects\RestaurantService\RestaurantDAO\BaseDAO.fs] namespace FSI_0106.RestaurantServiceDAO type BaseDAO = class new : unit -> BaseDAO member ExecNonQuery2 : conn:MySql.Data.MySqlClient.MySqlConnection -> sqlStr:string -> unit member execNonQuery : sqlStr:string -> unit member execQuery : sqlStr:string * selectFunc:(MySql.Data.MySqlClient.MySqlDataReader -> 'a list) -> 'a list member f : x:obj -> string member Conn : MySql.Data.MySqlClient.MySqlConnection end [Loading C:\Users\jblack\Documents\Visual Studio 2010\Projects\RestaurantService\RestaurantDAO\CreateDatabase.fs] C:\Users\jblack\Documents\Visual Studio 2010\Projects\RestaurantService\RestaurantDAO\CreateDatabase.fs(56,14): error FS0039: The field, constructor or member 'ExecNonQuery2' is not defined I am curious what I am doing wrong. I have tried not inheriting, and just instantiating the BaseDAO type in the function, but I get the same error. I started on this path because I had a property that had the same error, so it seems there may be a problem with how I am defining my BaseDAO type, but it compiles with no error, which further confuses me about this problem.

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• Prototypal inheritance should save memory, right?

  - by Techpriester

  Hi Folks, I've been wondering: Using prototypes in JavaScript should be more memory efficient than attaching every member of an object directly to it for the following reasons: The prototype is just one single object. The instances hold only references to their prototype. Versus: Every instance holds a copy of all the members and methods that are defined by the constructor. I started a little experiment with this: var TestObjectFat = function() { this.number = 42; this.text = randomString(1000); } var TestObjectThin = function() { this.number = 42; } TestObjectThin.prototype.text = randomString(1000); randomString(x) just produces a, well, random String of length x. I then instantiated the objects in large quantities like this: var arr = new Array(); for (var i = 0; i < 1000; i++) { arr.push(new TestObjectFat()); // or new TestObjectThin() } ... and checked the memory usage of the browser process (Google Chrome). I know, that's not very exact... However, in both cases the memory usage went up significantly as expected (about 30MB for TestObjectFat), but the prototype variant used not much less memory (about 26MB for TestObjectThin). I also checked: The TestObjectThin instances contain the same string in their "text" property, so they are really using the property of the prototype. Now, I'm not so sure what to think about this. The prototyping doesn't seem to be the big memory saver at all. I know that prototyping is a great idea for many other reasons, but I'm specifically concerned with memory usage here. Any explanations why the prototype variant uses almost the same amount of memory? Am I missing something?

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• C++ class is not being included properly.

  - by ravloony

  Hello all, I have a problem which is either something I have completely failed to understand, or very strange. It's probably the first one, but I have spent the whole afternoon googling with no success, so here goes... I have a class called Schedule, which has as a member a vector of Room. However, when I compile using cmake, or even by hand, I get the following: In file included from schedule.cpp:1: schedule.h:13: error: ‘Room’ was not declared in this scope schedule.h:13: error: template argument 1 is invalid schedule.h:13: error: template argument 2 is invalid schedule.cpp: In constructor ‘Schedule::Schedule(int, int, int)’: schedule.cpp:12: error: ‘Room’ was not declared in this scope schedule.cpp:12: error: expected ‘;’ before ‘r’ schedule.cpp:13: error: request for member ‘push_back’ in ‘((Schedule*)this)->Schedule::_sched’, which is of non-class type ‘int’ schedule.cpp:13: error: ‘r’ was not declared in this scope Here are the relevant bits of code: #include <vector> #include "room.h" class Schedule { private: std::vector<Room> _sched; //line 13 int _ndays; int _nrooms; int _ntslots; public: Schedule(); ~Schedule(); Schedule(int nrooms, int ndays, int ntslots); }; Schedule::Schedule(int nrooms, int ndays, int ntslots):_ndays(ndays), _nrooms(nrooms),_ntslots(ntslots) { for (int i=0; i<nrooms;i++) { Room r(ndays,ntslots); _sched.push_back(r); } } In theory, g++ should compile a class before the one that includes it. There are no circular dependencies here, it's all straightforward stuff. I am completely stumped on this one, which is what leads me to believe that I must be missing something. :-D

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• Working with complex objects in Prevayler commands

  - by alexantd

  The demos included in the Prevayler distribution show how to pass in a couple strings (or something simple like that) into a command constructor in order to create or update an object. The problem is that I have an object called MyObject that has a lot of fields. If I had to pass all of them into the CreateMyObject command manually, it would be a pain. So an alternative I thought of is to pass my business object itself into the command, but to hang onto a clone of it (keeping in mind that I can't store the BO directly in the command). Of course after executing this command, I would need to make sure to dispose of the original copy that I passed in. public class CreateMyObject implements TransactionWithQuery { private MyObject object; public CreateMyObject(MyObject business_obj) { this.object = (MyObject) business_obj.clone(); } public Object executeAndQuery(...) throws Exception { ... } } The Prevayler wiki says: Transactions can't carry direct object references (pointers) to business objects. This has become known as the baptism problem because it's a common beginner pitfall. Direct object references don't work because once a transaction has been serialized to the journal and then deserialized for execution its object references no longer refer to the intended objects - - any objects they may have referred to at first will have been copied by the serialization process! Therefore, a transaction must carry some kind of string or numeric identifiers for any objects it wants to refer to, and it must look up the objects when it is executed. I think by cloning the passed-in object I will be getting around the "direct object pointer" problem, but I still don't know whether or not this is a good idea...

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• Initializing objects on the fly

  - by pocoa

  I have a vector called players and a class called Player. And what I'm trying to do is to write: players.push_back(Player(name, Weapon(bullets))); So I want to be able to create players in a loop. But I see an error message says "no matching function for call Player::Player..." Then I've changed that to: Weapon w(bullets); Player p(name, w); players.push_back(p); Here is my Player definition: class Player { public: Player(string &name, Weapon &weapon); private string name; Weapon weapon; } I'm just trying to learn what is the difference between these definitions. And is this the right way to pass an object to an object constructor. Note: These are not my actual class definitions. I'm just trying to learn something about object oriented programming in C++ with coding it. I mean I know that Weapon should be initialized in Player :)

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• Set title and (title) icon for a custom alert dialog

  - by Ecki

  I don't manage to set a neither a title nor a (title) icon to my custom alert dialog. My code: public class AddingFavoriteDialog extends AlertDialog { . . . private OnAddingFavoriteListener onAddingFavoriteListener; private Context context; private GeocodingManager geocodingManager; private FavoritesActivity favoritesActivity; public AddingFavoriteDialog(Context context, OnAddingFavoriteListener onAddingFavoriteListener) { super(context, android.R.style.Theme_Dialog); this.context = context; this.onAddingFavoriteListener = onAddingFavoriteListener; this.geocodingManager = new GeocodingManager(context); this.favoritesActivity = (FavoritesActivity) context; } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.adding_favorite_dialog2); setTitle("MYTITLE"); setIcon(R.drawable.star_gold); . . . } What am i doing wrong? I also tried to set it by calling super.setTitle("MYTITLE"); in onCreate() as well as in the constructor.

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• Question about decorator pattern and the abstract decorator class?

  - by es11

  This question was asked already here, but rather than answering the specific question, descriptions of how the decorator pattern works were given instead. I'd like to ask it again because the answer is not immediately evident to me just by reading how the decorator pattern works (I've read the wikipedia article and the section in the book Head First Design Patterns). Basically, I want to know why an abstract decorator class must be created which implements (or extends) some interface (or abstract class). Why can't all the new "decorated classes" simply implement (or extend) the base abstract object themselves (instead of extending the abstract decorator class)? To make this more concrete I'll use the example from the design patterns book dealing with coffee beverages: There is an abstract component class called Beverage Simple beverage types such as HouseBlend simply extend Beverage To decorate beverage, an abstract CondimentDecorator class is created which extends Beverage and has an instance of Beverage Say we want to add a "milk" condiment, a class Milk is created which extends CondimentDecorator I'd like to understand why we needed the CondimentDecorator class and why the class Milk couldn't have simply extended the Beverage class itself and been passed an instance of Beverage in its constructor. Hopefully this is clear...if not I'd simply like to know why is the abstract decorator class necessary for this pattern? Thanks. Edit: I tried to implement this, omitting the abstract decorator class, and it seems to still work. Is this abstract class present in all descriptions of this pattern simply because it provides a standard interface for all of the new decorated classes?

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• nhibernate : Repository Session Management

  - by frosty

  At the moment my repository has 2 constructors. When i call these from my mvc website i am alway calling first constructor and thus opening a new session. Should i been passing in the session. How should i be doing this. public CompanyRepository() { _session = NHibernateHelper.OpenSession(); } public CompanyRepository(ISession session) { _session = session; } public class NHibernateHelper { private static ISessionFactory _sessionFactory; private static ISessionFactory SessionFactory { get { if (_sessionFactory == null) { var configuration = new Configuration(); configuration.Configure(); configuration.AddAssembly(typeof(UserProfile).Assembly); configuration.SetProperty(NHibernate.Cfg.Environment.ConnectionStringName, System.Environment.MachineName); _sessionFactory = configuration.BuildSessionFactory(); } return _sessionFactory; } } public static ISession OpenSession() { return SessionFactory.OpenSession(); } } I'm using the Ninject IOC container ( very new to me ). I have the following container. How would i bind the ISession to the CompanyRepository. private class EStoreDependencies : NinjectModule { public override void Load() { Bind<ICompanyRepository>().To<CompanyRepository>(); Bind<IUserProfileRepository>().To<UserProfileRepository>(); Bind<IAddressRepository>().To<AddressRepository>(); Bind<IRolesService>().To<AspNetRoleProviderWrapper>(); Bind<IUserService>().To<AspNetMembershipProviderWrapper>(); Bind<ICurrentUserSerivce>().To<DefaultCurrentUserSerivce>(); Bind<IPasswordService>().To<AspNetMembershipProviderWrapper>(); Bind<IStatusResponseRepository>().To<StatusResponseRepository>(); Bind<ICategoryRepository>().To<CategoryRepository>(); Bind<IProductRepository>().To<ProductRepository>(); } }

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• C# ref Confusion

  - by Rahat

  I have a confusion that when i pass a variable by refrence in the constructor of another class and after passing that object by refrence i recreate the refrence object with the new keyword. Now the class in which i have passed the refrenced object dosen't reflect the updated data. An exabple of the above problem is shown below: Object to be passed by Refrence: public class DummyObject { public string Name = "My Name"; public DummyObject() { } } Class which is passing the Refrence: public partial class Form1 : Form { // Object to be passed as refrence DummyObject dummyObject = new DummyObject(); public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { // assigning value dummyObject.Name = "I am Dummy"; // Passing object Form2 frm = new Form2(ref dummyObject); frm.Show(); } private void button2_Click(object sender, EventArgs e) { // Displaying Name MessageBox.Show(this.dummyObject.Name); } private void button3_Click(object sender, EventArgs e) { // Assigning new object this.dummyObject = new DummyObject(); // Changing Name Variable this.dummyObject.Name = "I am Rechanged"; // Displaying Name MessageBox.Show(this.dummyObject.Name); } } Class to which Object is passed by Reference: public partial class Form2 : Form { private DummyObject dummyObject = null; public Form2(ref DummyObject DummyObject) { InitializeComponent(); this.dummyObject = DummyObject; this.dummyObject.Name = "I am Changed"; } private void button2_Click(object sender, EventArgs e) { MessageBox.Show(this.dummyObject.Name); } } whn i reaasign the object in Form 1 and cdisplay its value in form 2 it still displays "I am Changed" instead of "I am Rechanged". How to keep the data synchronized?

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• [JAX-B] How can I ignore a superclass?

  - by MrSpandex

  I'm trying to write a web service for the java.util.logging api. So I wrote a class MyLogRecord that inherits from LogRecord. I annotated this class with JAX-B annotations, including @XmlAccessorType(XmlAccessType.NONE) so it would ignore non-annotated fields and properties. When I start up tomcat, I get errors that java.util.logging.Level and other java.util.logging classes do not have a default constructor, but none of my annotated methods make any reference to the Level class or any of the other java.util.logging classes. These are referenced by the parent class. My sub-class has everything it needs defined. How can I get JAX-B to ignore the parent class completely? Update: I found another post on this, which suggests modifying the parent class. This is obviously not possible because I am extending a java.util class. IS there any way to do this without modifying the superclass? Update2: I found a thread on java.net for a similar problem. That thread resulted in an enhancement request, which was marked as a duplicate of another issue, which resulted in the @XmlTransient annotation. The comments on these bug reports lead me to believe this is impossible in the current spec.

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• What happens when we combine RAII and GOTO ?

  - by Robert Gould

  I'm wondering, for no other purpose than pure curiosity (because no one SHOULD EVER write code like this!) about how the behavior of RAII meshes with the use of Goto (lovely idea isn't it). class Two { public: ~Two() { printf("2,"); } }; class Ghost { public: ~Ghost() { printf(" BOO! "); } }; void foo() { { Two t; printf("1,"); goto JUMP; } Ghost g; JUMP: printf("3"); } int main() { foo(); } When running the following code in VS2005 I get the following output: 1,2,3 BOO! However I imagined, guessed, hoped that 'BOO!' wouldn't actually appear as the Ghost should have never been instantiated (IMHO, because I don't know the actual expected behavior of this code). Any Guru out there knows what's up? Just realized that if I instantiate an explicit constructor for Ghost the code doesn't compile... class Ghost { public: Ghost() { printf(" HAHAHA! "); } ~Ghost() { printf(" BOO! "); } }; Ah, the mystery ...

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• Using generics in F# to create an EnumArray type

  - by Matthew

  I've created an F# class to represent an array that allocates one element for each value of a specific enum. I'm using an explicit constructor that creates a dictionary from enum values to array indices, and an Item property so that you can write expressions like: let my_array = new EnumArray<EnumType, int> my_array.[EnumType.enum_value] <- 5 However, I'm getting the following obscure compilation error at the line marked with '// FS0670' below. error FS0670: This code is not sufficiently generic. The type variable ^e when ^e : enum<int> and ^e : equality and ^e : (static member op_Explicit : ^e -> int) could not be generalized because it would escape its scope. I'm at a loss - can anyone explain this error? type EnumArray< 'e, 'v when 'e : enum<int> and 'e : equality and ^e : (static member op_Explicit : ^e -> int) > = val enum_to_int : Dictionary<'e, int> val a : 'v array new() as this = { enum_to_int = new Dictionary<'e, int>() a = Array.zeroCreate (Enum.GetValues(typeof<'e>).Length) } then for (e : obj) in Enum.GetValues(typeof<'e>) do this.enum_to_int.Add(e :?> 'e, int(e :?> 'e)) member this.Item with get (idx : 'e) : 'v = this.a.[this.enum_to_int.[idx]] // FS0670 and set (idx : 'e) (c : 'v) = this.a.[this.enum_to_int.[idx]] <- c

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• Can I get rid of this read lock?

  - by Pieter

  I have the following helper class (simplified): public static class Cache { private static readonly object _syncRoot = new object(); private static Dictionary<Type, string> _lookup = new Dictionary<Type, string>(); public static void Add(Type type, string value) { lock (_syncRoot) { _lookup.Add(type, value); } } public static string Lookup(Type type) { string result; lock (_syncRoot) { _lookup.TryGetValue(type, out result); } return result; } } Add will be called roughly 10/100 times in the application and Lookup will be called by many threads, many of thousands of times. What I would like is to get rid of the read lock. How do you normally get rid of the read lock in this situation? I have the following ideas: Require that _lookup is stable before the application starts operation. The could be build up from an Attribute. This is done automatically through the static constructor the attribute is assigned to. Requiring the above would require me to go through all types that could have the attribute and calling RuntimeHelpers.RunClassConstructor which is an expensive operation; Move to COW semantics. public static void Add(Type type, string value) { lock (_syncRoot) { var lookup = new Dictionary<Type, string>(_lookup); lookup.Add(type, value); _lookup = lookup; } } (With the lock (_syncRoot) removed in the Lookup method.) The problem with this is that this uses an unnecessary amount of memory (which might not be a problem) and I would probably make _lookup volatile, but I'm not sure how this should be applied. (John Skeets' comment here gives me pause.) Using ReaderWriterLock. I believe this would make things worse since the region being locked is small. Suggestions are very welcome.

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• Jasmine testing coffeescript expect(setTimeout).toHaveBeenCalledWith

  - by Lee Quarella

  In the process of learning Jasmine, I've come to this issue. I want a basic function to run, then set a timeout to call itself again... simple stuff. class @LoopObj constructor: -> loop: (interval) -> #do some stuff setTimeout((=>@loop(interval)), interval) But I want to test to make sure the setTimeout was called with the proper args describe "loop", -> xit "does nifty things", -> it "loops at a given interval", -> my_nifty_loop = new LoopObj interval = 10 spyOn(window, "setTimeout") my_nifty_loop.loop(interval) expect(setTimeout).toHaveBeenCalledWith((-> my_nifty_loop.loop(interval)), interval) I get this error: Expected spy setTimeout to have been called with [ Function, 10 ] but was called with [ [ Function, 10 ] ] Is this because the (-> my_nifty_loop.loop(interval)) function does not equal the (=>@loop(interval)) function? Or does it have something to do with the extra square brackets around the second [ [ Function, 10 ] ]? Something else altogther? Where have I gone wrong?

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• How do I mock a method with an open array parameter in PascalMock?

  - by Oliver Giesen

  I'm currently in the process of getting started with unit testing and mocking for good and I stumbled over the following method that I can't seem to fabricate a working mock implementation for: function GetInstance(const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID = CID_DEFAULT): Boolean; (TImplContextID is just an alias for Integer) I thought it would have to look something like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; begin Result := AddCall('GetInstance') .WithParams([@AIID, AContextID]) .ReturnsOutParams([AInstance]) .ReturnValue; end; But the compiler complains about the .ReturnsOutParams([AInstance]) saying "Bad argument type in variable type array constructor.". Also I haven't found a way to specify the open array parameter AArgs at all. Also, is using the @-notation for the TGUID-typed parameter the right way to go? Is it possible to mock this method with the current version of PascalMock at all? Update: I now realize I got the purpose of ReturnsOutParams completely wrong: It's intended to be used for populating the values to be returned when defining the expectations rather than for mocking the call itself. I now think the correct syntax for mocking the out parameter would probably have to look more like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; var lCall: TMockMethod; begin lCall := AddCall('GetInstance').WithParams([@AIID, AContextID]); Pointer(AInstance) := lCall.OutParams[0]; Result := lCall.ReturnValue; end; The questions that remain are how to mock the open array parameter AArgs and whether passing the TGUID argument (i.e. a value type) by address will work out...

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• Returning object from function

  - by brainydexter

  I am really confused now on how and which method to use to return object from a function. I want some feedback on the solutions for the given requirements. Scenario A: The returned object is to be stored in a variable which need not be modified during its lifetime. Thus, const Foo SomeClass::GetFoo() { return Foo(); } invoked as: someMethod() { const Foo& l_Foo = someClassPInstance->GetFoo(); //... } Scneraio B: The returned object is to be stored in a variable which will be modified during its lifetime. Thus, void SomeClass::GetFoo(Foo& a_Foo_ref) { a_Foo_ref = Foo(); } invoked as: someMethod() { Foo l_Foo; someClassPInstance-GetFoo(l_Foo); //... } I have one question here: Lets say that Foo cannot have a default constructor. Then how would you deal with that in this situation, since we cant write this anymore: Foo l_Foo Scenario C: Foo SomeClass::GetFoo() { return Foo(); } invoked as: someMethod() { Foo l_Foo = someClassPInstance->GetFoo(); //... } I think this is not the recommended approach since it would incur constructing extra temporaries. What do you think ? Also, do you recommend a better way to handle this instead ?

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• KeyStore, HttpClient, and HTTPS: Can someone explain this code to me?

  - by stormin986

  I'm trying to understand what's going on in this code. KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType()); FileInputStream instream = new FileInputStream(new File("my.keystore")); try { trustStore.load(instream, "nopassword".toCharArray()); } finally { instream.close(); } SSLSocketFactory socketFactory = new SSLSocketFactory(trustStore); Scheme sch = new Scheme("https", socketFactory, 443); httpclient.getConnectionManager().getSchemeRegistry().register(sch); My Questions: trustStore.load(instream, "nopassword".toCharArray()); is doing what exactly? From reading the documentation load() will load KeyStore data from an input stream (which is just an empty file we just created), using some arbitrary "nopassword". Why not just load it with null as the InputStream parameter and an empty string as the password field? And then what is happening when this empty KeyStore is being passed to the SSLSocketFactory constructor? What's the result of such an operation? Or -- is this simply an example where in a real application you would have to actually put a reference to an existing keystore file / password?

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• Html.ListBox() and MultiselectList

  - by Ivan90

  Hi guys, I've a little problem with an Html.ListBox! I am developing a personal blog in ASP.NET MVC 1.0 and I created an adminpanel where I can add and edit a post! During this two operations, I can add also tags! I think of use an Html.ListBox() helper to list all tags, and so I can select multiple tags to add in a post! The problem isn't during the add mode, but in the edit mode, where I have to pre-select post's tags! I read that I have to use a MultiSelectList and so in its constructor pass, tags' list and tag's list(pre-selected value). But I don't know how to use this class! I post, some code: This is my models method that get all list tags in selectlist public IEnumerable<SelectListItem> GetTagsListBox() { return from t in db.Tags orderby t.IDTag descending select new SelectListItem { Text = t.TagName, Value = t.IDTag.ToString(), }; } So in Edit (Get and Post), Add(Get and Post) I use a ViewData to pass this list in Html.ListBox(). ViewData["Tags"] = tagdb.GetTagsListBox(); And in my view <%=Html.ListBox("Tags",ViewData["Tags"] as SelectList) %> So with this code it's ok in Add Mode! But in Edit Mode I need to pre-select those values! So Now, of course I have to create a method that get all tagsbypostid! and then in ViewData what Must I to pass? Any suggest?

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• Remove pointer object whose reference is mantained in three different lists

  - by brainydexter

  I am not sure how to approach this problem: 'Player' class mantains a list of Bullet* objects: class Player { protected: std::list< Bullet* > m_pBullet_list; } When the player fires a Bullet, it is added to this list. Also, inside the constructor of bullet, a reference of the same object is updated in CollisionMgr, where CollisionMgr also mantains a list of Bullet*. Bullet::Bullet(GameGL*a_pGameGL, Player*a_pPlayer) : GameObject( a_pGameGL ) { m_pPlayer = a_pPlayer; m_pGameGL->GetCollisionMgr()->AddBullet(this); } class CollisionMgr { void AddBullet(Bullet* a_pBullet); protected: std::list< Bullet*> m_BulletPList; } In CollisionMgr.Update(); based on some conditions, I populate class Cell which again contain a list of Bullet*. Finally, certain conditions qualify a Bullet to be deleted. Now, these conditions are tested upon while iterating through a Cell's list. So, if I have to delete the Bullet object, from all these places, how should I do it so that there are no more dangling references to it? std::list< Bullet*>::iterator bullet_it; for( bullet_it = (a_pCell->m_BulletPList).begin(); bullet_it != (a_pCell->m_BulletPList).end(); bullet_it++) { bool l_Bullet_trash = false; Bullet* bullet1 = *bullet_it; // conditions would set this to true if ( l_Bullet_Trash ) // TrashBullet( bullet1 ); continue; } Also, I was reading about list::remove, and it mentions that it calls the destructor of the object we are trying to delete. Given this info, if I delete from one list, the object does not exist, but the list would still contain a reference to it..How do I handle all these problems ? Can someone please help me here ? Thanks PS: If you want me to post more code or provide explanation, please do let me know.

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• 'C++ object destroyed' in QComboBox descendant editor in delegate

  - by Max

  Hi, all! I have modified combobox to hold colors, using QtColorCombo (http://qt.nokia.com/products/appdev/add-on-products/catalog/4/Widgets/qtcolorcombobox) as howto for the 'more...' button implementation details. It works fine in C++ and in PyQt on linux, but I get 'underlying C++ object was destroyed' when use this control in PyQt on Windows. It seels like the error happens when: ... # in constructor: self.activated.connect(self._emitActivatedColor) ... def _emitActivatedColor(self, index): if self._colorDialogEnabled and index == self.colorCount(): print '!!!!!!!!! QtGui.QColorDialog.getColor()' c = QtGui.QColorDialog.getColor() # <----- :( delegate fires 'closeEditor' print '!!!!!!!!! ' + c.name() if c.isValid(): self._numUserColors += 1 #at the next line currentColor() tries to access C++ layer and fails self.addColor(c, self.currentColor().name()) self.setCurrentIndex(index) ... Maybe console output will help. I've overridden event() in editor and got: ... MouseButtonRelease FocusOut Leave Paint Enter Leave FocusIn !!!!!!!!! QtGui.QColorDialog.getColor() WindowBlocked Paint WindowDeactivate !!!!!!!!! 'CloseEditor' fires! Hide HideToParent FocusOut DeferredDelete !!!!!!!!! #6e6eff ... Can someone explain, why there is such a different behaviour in the different environments, and maybe give a workaround to fix this. Here is minimal example: http://docs.google.com/Doc?docid=0Aa0otNVdbWrrZDdxYnF3NV80Y20yam1nZHM&hl=en

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• Textfield - what is wxTextCtrlNameStr?

  - by Wallter

  I'm trying to create a basic wxWidgets program with a text entry box, in the constructor there is a variable wxTextCtrlNameStr - in researching I can't seem to find wxTextCtrlNameStr? any help? wxTextCtrl(wxWindow* parent, wxWindowID id, const wxString& value = "", const wxPoint& pos = wxDefaultPosition, const wxSize& size = wxDefaultSize, long style = 0, const wxValidator& validator = wxDefaultValidator, const wxString& name = wxTextCtrlNameStr) My Code: MainFrame::MainFrame(const wxString& title) : wxFrame(NULL, wxID_ANY, title) { wxButton * Centigrade = new wxButton(this, BUTTON_CENTIGRADE, _T("to Centigrade"), wxPoint(20, 20), wxDefaultSize, 0); wxButton * Fahrenheit = new wxButton(this, BUTTON_FAHRENHEIT, _T("to Fahrenheit"), wxPoint(20, 40), wxDefaultSize, 0); F_txt = new wxTextCtrl(this, TXT_F_Main, "0", wxDefaultPosition, wxDefaultSize, wxDefaultValidator, wxTextCtrlNameStr); /***********************************************/ C_txt = new wxTextCtrl(this, TXT_C_Main, "0", wxDefaultPosition, wxDefaultSize, wxDefaultValidator, wxTextCtrlNameStr); /***********************************************/ ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...

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• What is the best way to return result from business layer to presentation layer when using linq - I

  - by samsur

  I have a business layer that has DTOs that are used in the presentation layer. This application uses entity framework. Here is an example of a class called RoleDTO public class RoleDTO { public Guid RoleId { get; set; } public string RoleName { get; set; } public string RoleDescription { get; set; } public int? OrganizationId { get; set; } } In the BLL I want to have a method that returns a list of DTO.. I would like to know which is the better approach: returning IQueryable or list of DTOs. Although i feel that returning Iqueryable is not a good idea because the connection needs to be open. Here are the 2 different methods using the different approaches public class RoleBLL { private servicedeskEntities sde; public RoleBLL() { sde = new servicedeskEntities(); } public IQueryable<RoleDTO> GetAllRoles() { IQueryable<RoleDTO> role = from r in sde.Roles select new RoleDTO() { RoleId = r.RoleID, RoleName = r.RoleName, RoleDescription = r.RoleDescription, OrganizationId = r.OrganizationId }; return role; } Note: in the above method the datacontext is a private attribute and set in the constructor, so that the connection stays opened. Second approach public static List GetAllRoles() { List roleDTO = new List(); using (servicedeskEntities sde = new servicedeskEntities()) { var roles = from pri in sde.Roles select new { pri.RoleID, pri.RoleName, pri.RoleDescription }; //Add the role entites to the DTO list and return. This is necessary as anonymous types can be returned acrosss methods foreach (var item in roles) { RoleDTO roleItem = new RoleDTO(); roleItem.RoleId = item.RoleID; roleItem.RoleDescription = item.RoleDescription; roleItem.RoleName = item.RoleName; roleDTO.Add(roleItem); } return roleDTO; } Please let me know, if there is a better approach - Thanks,

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• Mutual class instances in C++

  - by SepiDev

  Hi guys. What is the issue with this code? Here we have two files: classA.h and classB.h classA.h: #ifndef _class_a_h_ #define _class_a_h_ #include "classB.h" class B; //???? class A { public: A() { ptr_b = new B(); //???? } virtual ~A() { if(ptr_b) delete ptr_b; //???? num_a = 0; } int num_a; B* ptr_b; //???? }; #endif //_class_a_h_ classB.h: #ifndef _class_b_h_ #define _class_b_h_ #include "classA.h" class A; //???? class B { public: B() { ptr_a = new A(); //???? num_b = 0; } virtual ~B() { if(ptr_a) delete ptr_a; //???? } int num_b; A* ptr_a; //???? }; #endif //_class_b_h_ when I try to compile it, the compiler (g++) says: classB.h: In constructor ‘B::B()’: classB.h:12: error: invalid use of incomplete type ‘struct A’ classB.h:6: error: forward declaration of ‘struct A’ classB.h: In destructor ‘virtual B::~B()’: classB.h:16: warning: possible problem detected in invocation of delete operator: classB.h:16: warning: invalid use of incomplete type ‘struct A’ classB.h:6: warning: forward declaration of ‘struct A’ classB.h:16: note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined.

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• How is a functional programming-based javascript app laid out?

  - by user321521

  I've been working with node.js for awhile on a chat app (I know, very original, but I figured it'd be a good learning project). Underscore.js provides a lot of functional programming concepts which look interesting, so I'd like to understand how a functional program in javascript would be setup. From my understanding of functional programming (which may be wrong), the whole idea is to avoid side effects, which are basically having a function which updates another variable outside of the function so something like var external; function foo() { external = 'bar'; } foo(); would be creating a side effect, correct? So as a general rule, you want to avoid disturbing variables in the global scope. Ok, so how does that work when you're dealing with objects and what not? For example, a lot of times, I'll have a constructor and an init method that initializes the object, like so: var Foo = function(initVars) { this.init(initVars); } Foo.prototype.init = function(initVars) { this.bar1 = initVars['bar1']; this.bar2 = initVars['bar2']; //.... } var myFoo = new Foo({'bar1': '1', 'bar2': '2'}); So my init method is intentionally causing side effects, but what would be a functional way to handle the same sort of situation? Also, if anyone could point me to either a python or javascript source code of a program that tries to be as functional as possible, that would also be much appreciated. I feel like I'm close to "getting it", but I'm just not quite there. Mainly I'm interested in how functional programming works with traditional OOP classes concept (or does away with it for something different if that's the case).

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• Immutable classes in C++

  - by ereOn

  Hi, In one of my projects, I have some classes that represent entities that cannot change once created, aka. immutable classes. Example : A class RSAKey that represent a RSA key which only has const methods. There is no point changing the existing instance: if you need another one, you just create one. My objects sometimes are heavy and I enforced the use of smart pointers to avoid copy. So far, I have the following pattern for my classes: class RSAKey : public boost::noncopyable, public boost::enable_shared_from_this<RSAKey> { public: /** * \brief Some factory. * \param member A member value. * \return An instance. */ static boost::shared_ptr<const RSAKey> createFromMember(int member); /** * \brief Get a member. * \return The member. */ int getMember() const; private: /** * \brief Constructor. * \param member A member. */ RSAKey(int member); /** * \brief Member. */ const int m_member; }; So you can only get a pointer (well, a smart pointer) to a const RSAKey. To me, it makes sense, because having a non-const reference to the instance is useless (it only has const methods). Do you guys see any issue regarding this pattern ? Are immutable classes something common in C++ or did I just created a monster ? Thank you for your advices !

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