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This technique achieves a similar effect to the use of virtual functions, without the costs (and some flexibility) of dynamic polymorphism. This particular use of the CRTP has been called "simulated dynamic binding" by some. [10] This pattern is used extensively in the Windows ATL and WTL libraries.
Languages that separate the programmatic interface of objects from the implementation, like Visual Basic and Delphi, also tend to use this approach, because it allows objects to use a different implementation simply by using a different set of method pointers. The method allows creation of external libraries, where other techniques perhaps may not.
Dynamic dispatch contrasts with static dispatch, in which the implementation of a polymorphic operation is selected at compile time. The purpose of dynamic dispatch is to defer the selection of an appropriate implementation until the run time type of a parameter (or multiple parameters) is known.
In computing, late binding or dynamic linkage [1] —though not an identical process to dynamically linking imported code libraries—is a computer programming mechanism in which the method being called upon an object, or the function being called with arguments, is looked up by name at runtime.
Polymorphism can be distinguished by when the implementation is selected: statically (at compile time) or dynamically (at run time, typically via a virtual function). This is known respectively as static dispatch and dynamic dispatch, and the corresponding forms of polymorphism are accordingly called static polymorphism and dynamic polymorphism.
The concept of the virtual function solves the following problem: In object-oriented programming, when a derived class inherits from a base class, an object of the derived class may be referred to via a pointer or reference of the base class type instead of the derived class type.
Composition over inheritance (or composite reuse principle) in object-oriented programming (OOP) is the principle that classes should favor polymorphic behavior and code reuse by their composition (by containing instances of other classes that implement the desired functionality) over inheritance from a base or parent class. [2]
Thought dates = new Advice (); // Polymorphism dates. message (); // Prints "Warning: Dates in calendar are closer than they appear." When a subclass contains a method that overrides a method of the superclass, then that (superclass's) overridden method can be explicitly invoked from within a subclass's method by using the keyword super . [ 3 ] (