derived-class

I've been trying this, but I can't seem to figure this out. I want to do this... public abstract class SingletonType<TSingleton, TBaseClass> : TBaseClass where TSingleton : TBaseClass, new() where TBaseClass : class { static TSingleton _singleton; public static TSingleton Singleton => _singleton ?? (_singleton = new TSingleton()); } The plan was to use it like this which would sort of 'wrap' the singleton pattern around a base class... public class SingletonFoo : SingletonType<SingletonFoo, Foo> { } However, I keep getting this Cannot derive from 'TBaseClass' because it is a type parameter Um.

I have seen many times an Interface instance generated from a class. Why does use an Interface in this way? An Interface instance created only itself with the help of the derived class and we can access only this interface members through this instance. How does this give an advantage? I'm so confused.. interface IPrint { void Print(); } class Sample : IPrint { public void Print() { Console.WriteLine("Print..."); } public void Sample() { Console.WriteLine("Sample..."); } } class Program { static void Main(string[] args) { IPrint print = new Sample(); print.Print(); } } Interfaces define that a

Is there any way to, in a Java derived class, "disable" a method and/or field that is otherwise inherited from a base class? For example, say you have a Shape base class that has a rotate() method. You also have various types derived from the Shape class: Square , Circle , UpwardArrow , etc. Shape has a rotate() method. But I don't want rotate() to be available to the users of Circle , because it's pointless, or users of UpwardArrow , because I don't want UpwardArrow to be able to rotate. I don't think it is possible. However you can further refine the Shape class by removing the rotate()

How to stop the class to be inherited by other class. Nawaz C++11 solution In C++11, you can seal a class by using final keyword in the definition as: class A final //note final keyword is used after the class name { //... }; class B : public A //error - because class A is marked final (sealed). { // so A cannot be derived from. //... }; To know the other uses of final, see my answer here: What is the purpose of the "final" keyword in C++11 for functions? C++03 solution Bjarne Stroustrup's code : Can I stop people deriving from my class? class Usable; class Usable_lock { friend class Usable;

If I allocate an object of a class Derived (with a base class of Base ), and store a pointer to that object in a variable that points to the base class, how can I access the members of the Derived class? Here's an example: class Base { public: int base_int; }; class Derived : public Base { public: int derived_int; }; Base* basepointer = new Derived(); basepointer-> //Access derived_int here, is it possible? If so, then how? No, you cannot access derived_int because derived_int is part of Derived , while basepointer is a pointer to Base . You can do it the other way round though: Derived*