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In the delegate pattern, this is instead accomplished by explicitly passing the original object to the delegate, as an argument to a method. [1] " Delegation" is often used loosely to refer to the distinct concept of forwarding , where the sending object simply uses the corresponding member on the receiving object, evaluated in the context of ...
Translating the implicit this into an explicit parameter, the call (in B, with a a delegate) a.foo() translates to A.foo(b), using the type of a for method resolution, but the delegating object b for the this argument. Using inheritance, the analogous code (using capital letters to emphasize that resolution is based on classes, not objects) is:
Delegate (CLI), a form of type-safe function pointer used by the Common Language Infrastructure (CLI), specifying both a method to call and optionally an object to call the method on. See also [ edit ]
C# implements object-oriented method pointers in the form of delegates. A delegate is a special type that can capture a reference to a method. This reference can then be stored in a delegate-type variable or passed to a method through a delegate parameter for later invocation.
Java provides default interface methods since version 8. [4]: 104 Project Lombok [13] supports delegation using the @Delegate annotation on the field, instead of copying and maintaining the names and types of all the methods from the delegated field. [14] Julia macros can be used to generate forwarding
The Factory handles the mapping of decorator and delegate classes and returns the pair associated with a parameter or parameters passed. The interface is the contract between a decorator, a delegate, and the calling class, creating an Inversion of Responsibility. [1] This example use two branches; however, you can have 'N' branches as required.
In object-oriented programming, the factory method pattern is a design pattern that uses factory methods to deal with the problem of creating objects without having to specify their exact classes. Rather than by calling a constructor , this is accomplished by invoking a factory method to create an object.
In this Java example, the Printer class has a print method. This print method, rather than performing the print itself, forwards to an object of class RealPrinter. To the outside world it appears that the Printer object is doing the print, but the RealPrinter object is the one actually doing the work.