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  • C2664 when casting child class to templated parent class

    - by DC
    I have a parent class which is templated, and a child class which implements it. template< typename T1, typename T2> class ParentClass{ . . . }; class ChildClass : public ParentClass<MyT1, MyT2> { . . . }; And I want to have a pointer which I can use polymorphically: ParentClass<T1, T2>* ptr; ptr = static_cast<ParentClass<MyT1, MyT2>* >(new ChildClass() ); No matter how I cast it, I always get a C2664 which has the same expression: error C2664: cannot convert parameter 1 from 'ParentClass< T1,T2 *' to 'ParentClass< T1,T2 *' Is it not possible to cast pointer types between inherited types if the parent is templated, even if the types specified in the templates are the same?

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  • noncopyable static const member class in template class

    - by Dukales
    I have a non-copyable (inherited from boost::noncopyable) class that I use as a custom namespace. Also, I have another class, that uses previous one, as shown here: #include <boost/utility.hpp> #include <cmath> template< typename F > struct custom_namespace : boost::noncopyable { F sqrt_of_half(F const & x) const { using std::sqrt; return sqrt(x / F(2.0L)); } // ... maybe others are not so dummy const/constexpr methods }; template< typename F > class custom_namespace_user { static ::custom_namespace< F > const custom_namespace_; public : F poisson() const { return custom_namespace_.sqrt_of_half(M_PI); } static F square_diagonal(F const & a) { return a * custom_namespace_.sqrt_of_half(1.0L); } }; template< typename F > ::custom_namespace< F > const custom_namespace_user< F >::custom_namespace_(); this code leads to the next error (even without instantiation): error: no 'const custom_namespace custom_namespace_user::custom_namespace_()' member function declared in class 'custom_namespace_user' The next way is not legitimate: template< typename F ::custom_namespace< F const custom_namespace_user< F ::custom_namespace_ = ::custom_namespace< F (); What should I do to declare this two classes (first as noncopyable static const member class of second)? Is this feaseble?

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  • PHP access class inside another class

    - by arxanas
    So I have two classes like this: class foo { /* code here */ } $foo = new foo(); class bar { global $foo; public function bar () { echo $foo->something(); } } I want to access the methods of foo inside all methods bar, without declaring it in each method inside bar, like this: class bar { public function bar () { global $foo; echo $foo->something(); } public function barMethod () { global $foo; echo $foo->somethingElse(); } /* etc */ } I don't want to extend it, either. I tried using the var keyword, but it didn't seem to work. What do I do in order to access the other class "foo" inside all methods of bar?

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  • Different return value of an overridden class

    - by Samer Afach
    I have a simple but confusing question here. Is it legal to have a different return value type for overridden methods than the abstact ones defined in the base class?? I did that and the compiler didn't complain... could someone please explain? class MyBaseClass { int value; public: virtual int getValue() = 0; }; class MyClass : public MyBaseClass { double value; public: virtual double getValue(); // here!!! return is double, not int }; double MyClass::getValue() { return this->value; } The compiler totally accepted something similar (MSVC und MinGW)... could anyone please exaplain to what extent this is legal?

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  • C# class in a directory without having the directory name in its namespace

    - by PaN1C_Showt1Me
    Hi ! If you add a directory in your Visual Studio project and you add a class inside it, the namespace will respect the whole path the directory inclusive. But sometimes, I prefer having the class in the main project namespace, although it lies in a directory structure, just because I don't want to have mess in my code. So often happens that I rewrite the Myproject.MyDirectory namespace to be Myproject only. Is it OK in your opinion? Or does any convention say that every class inside the directory must have it included in the namespace ? Thanks

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  • iPhone - Launching selectors from a different class

    - by David Schiefer
    Hi, I'd like to reload a table view which is in another class called "WriteIt_MobileAppDelegate" from one of my other classes which is called "Properties". I've tried to do this via the NSNotificationCenter class - the log gets called but the table is never updated. Properties.h: [[NSNotificationCenter defaultCenter] postNotificationName:@"NameChanged" object:[WriteIt_MobileAppDelegate class] userInfo:nil]; WriteIt_MobileAppDelegate.m -(void)awakeFromNib { [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reloadItProperties:) name:@"NameChanged" object:self]; } - (void) reloadItProperties: (NSNotification *)notification { NSLog(@"Reloading Data"); //this gets called [self.navigationController popToRootViewControllerAnimated:YES]; [self.tblSimpleTable reloadData]; [self.tblSimpleTable reloadSectionIndexTitles]; // but the rest doesn't } What am I doing wrong here?

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  • generating class from hibernate mapping file

    - by Mrityunjay
    hi, i have one mapping file viz. student.hbm.xml.. i need to generate Student.java from the same. the file is below :- <?xml version="1.0" encoding="UTF-8"?> <hibernate-mapping> <class name="org.hibernate.entity.ClassRoom" table="class_room"> <id name="roomId" column="room_id" type="int"/> <property name="roomClass" column="room_class" type="string"/> <property name="floor" column="floor" type="int"/> <property name="roomMaster" column="room_mast" type="string"/> </class> </hibernate-mapping> is there any way i can create the class file from the above file.please help...

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  • Why do Java source files go into a directory structure?

    - by bdhar
    Suppose that I am creating a Java project with the following classes com.bharani.ClassOne com.bharani.ClassTwo com.bharani.helper.HelperOne com.bharani.helper.support.HelperTwo with files put immediately under the folder 'src' src/ClassOne.java src/ClassTwo.java src/HelperOne.java src/HelperTwo.java and compile them using the command $ javac src/*.java -d classes (assuming that classes directory exists) The compiler compiles these files and put the class files in appropriate sub-directories inside the 'classes' directory like this classes/com/bharani/ClassOne.class classes/com/bharani/ClassTwo.class classes/com/bharani/helper/HelperOne.class classes/com/bharani/helper/support/HelperTwo.class Because the spec mandates that the classes should go inside appropriate directory structure. Fine. My question is this: When I use an IDE such as Eclipse or NetBeans, they create the directory structure for the source code directory ('src' directory here) also. Why is that? Is it mandatory? Or, is it just a convention? Thanks.

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  • access property value of one class from another internal class in C#

    - by starz26
    how do i acces the property value from an internal class , see below? namespace N1 { public class ClassA { string var1 = null; private ClassB b; public ClassA() { var1 = "one"; b = new ClassB(); } //property public string Var1 { get{ return var1; } } } namespace N1 { internal class ClassB { private void method() { // I need to access the value of Var1( property) from here, how to do this? } } }

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  • Python: Hack to call a method on an object that isn't of its class

    - by cool-RR
    Assume you define a class, which has a method which does some complicated processing: class A(object): def my_method(self): # Some complicated processing is done here return self And now you want to use that method on some object from another class entirely. Like, you want to do A.my_method(7). This is what you'd get: TypeError: unbound method my_method() must be called with A instance as first argument (got int instance instead). Now, is there any possibility to hack things so you could call that method on 7? I'd want to avoid moving the function or rewriting it. (Note that the method's logic does depend on self.) One note: I know that some people will want to say, "You're doing it wrong! You're abusing Python! You shouldn't do it!" So yes, I know, this is a terrible terrible thing I want to do. I'm asking if someone knows how to do it, not how to preach to me that I shouldn't do it.

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  • C++: Create abstract class with abstract method and override the method in a subclass

    - by Martijn Courteaux
    Hi, How to create in C++ an abstract class with some abstract methods that I want to override in a subclass? How should the .h file look? Is there a .cpp, if so how should it look? In Java it would look like this: abstract class GameObject { public abstract void update(); public abstract void paint(Graphics g); } class Player extends GameObject { @Override public void update() { // ... } @Override public void paint(Graphics g) { // ... } } // In my game loop: for (int i = 0; i < objects.size(); i++) { objects.get(i).update(); } for (int i = 0; i < objects.size(); i++) { objects.get(i).paint(g); } Translating this code to C++ is enough for me.

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  • Trouble Copying custom class initialization

    - by Parad0x13
    I have a custom class of type NSObject that contains a single NSMutableArray. This class is called Mutable2DArray and is designed to emulate a 2 dimensional array of type NSMutableArray. There is a custom init method - (id)initWithX:(int)x Y:(int)y that asks for the dimensions for the array and allocates the required arrays within the only array the class owns. My issue is when I try to copy an instance of Mutable2DArray I get an error saying the copyWithZone is an unrecognized selector. I thought copy was a base method of NSObject so I'm confused why I cant create a copy of the instance like this: Mutable2DArray *Array1 = [[Mutable2DArray alloc] initWithX:10 Y:10]; Mutable2DArray *Array2 = [Array1 copy]; Am I missing something so obvious here?

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  • Confused about Base class libary and Framework Class Library

    - by n0vic3c0d3r
    Is ADO.NET and ASP.NET a part of Base Class Library? The information given in wikipedia looks ambiguous to me. In the figure, it is shown as a separate block. What is the difference between Base Class Library(BCL) and Framework Class Library(FCL)? Is FCL as a part of .NET Framework? If so why is FCL not shown in the figure as part of .NET framework? Got confused!!

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  • Defining private static class member

    - by mnn
    class B { /* ... */ }; class A { public: A() { obj = NULL; } private: static B* obj; }; However this produces huge mass of linker errors that symbol obj is unresolved. What's the "correct" way to have such private static class member without these linker errors? Edit: I tried this: B *A::obj = NULL; but I got about same amount of linker errors however this time about already defining A::obj. (LNK2005). Also I get LNK4006 warnings, also about A::obj

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  • Using control from a separate class in C#

    - by DazSlayer
    I have a program that dynamically creates controls when it starts, it works just fine when the code to do this is in the class of the actual form. I tried moving the code to a separate class and found that I could not use Controls.Add(). How can I add controls to the Form from a separate class? This is what I have so far: TextBox txtbx = new TextBox(); txtbx.Text = "asd" + x.ToString(); txtbx.Name = "txtbx" + x.ToString(); txtbx.Location = new Point(10, (20 * x)); txtbx.Height = 20; txtbx.Width = 50; Controls.Add(txtbx); Error 1 The name 'Controls' does not exist in the current context

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  • C# cross class enum visibility - Possible?

    - by 537mfb
    so i have a class ClassA that contains an enum MyEnum, and a class ClassB that references that class (different Projects) and so in ClassB i have a using ClassA; clause and i can access that enum using something like MyEnum value = MyEnum.EnumValue; Now on a third project i have my Windows form and it has a clause like using ClassB; Now what can i add in ClassB to acess that enum on my windows Form? Is it even Possible? i would like to avoid having to add ClassA to my form just to access an enum. The idea is that ClassB is sort of a manager between my form and the functionality in ClassA - but i would like to get access to that enum as it makes a lot of tasks easier

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  • Software to create folder structure

    - by Arthor
    When we create a project, company or whatever we use a folder structure. Is there a software that can allow us to create a folder structure like that of visio and then export the folder structure out and also update existing folder structure with an NEW folders that are added to the folder structure? I do not want to just copy and paste, but rather a use a software to help and create a few templates. Thanks

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  • Static member object of a class in the same class

    - by Luv
    Suppose we have a class as class Egg { static Egg e; int i; Egg(int ii):i(ii) {} Egg(const Egg &); //Prevents copy-constructor to be called public: static Egg* instance() {return &e} }; Egg Egg::e(47); This code guarantees that we cannot create any object, but could use only the static object. But how could we declare static object of the same class in the class. And also one thing more since e is a static object, and static objects can call only static member functions, so how could the constructor been called here for static object e, also its constructors are private.

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  • Converting a PHP array to class variables.

    - by animuson
    Simple question, how do I convert an associative array to variables in a class? I know there is casting to do an (object) $myarray or whatever it is, but that will create a new stdClass and doesn't help me much. Are there any easy one or two line methods to make each $key => $value pair in my array into a $key = $value variable for my class? I don't find it very logical to use a foreach loop for this, I'd be better off just converting it to a stdClass and storing that in a variable, wouldn't I? class MyClass { var $myvar; // I want variables like this, so they can be references as $this->myvar function __construct($myarray) { // a function to put my array into variables } }

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  • Difference between var and Class class in object creation

    - by Divine
    Its a silly question, however shocked to see different behaviors. Learning a lot. Lets say I have two classes below Class A { public void Display() { } } Class B : A { public void Display() { } } Class C : B { public void Display() { } } Class Final { static void Main() { var c = new C(); // B c = new C(); //My doubt is, both of the above gives different results. May I know B c = new C() creates object of B or C? What I understood is, it creates object of B. Then why we say "new C()"? I agree with C c = new C(); But I thought, B b = new C(); creates object of B. Where we use this style? Only when utilizing runtime polymorphism? (Overriding methods)? } }

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  • What is the best design to this class?

    - by HPT
    assume this class: public class Logger { static TextWriter fs = null; public Logger(string path) { fs = File.CreateText(path); } public static void Log(Exception ex) { ///do logging } public static void Log(string text) { ///do logging } } and I have to use this like: Logger log = new Logger(path); and then use Logger.Log() to log what I want. the question is: is this a good design? to instantiate a class and then always call it's static method? any suggestion yield in better design is appreciated.

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