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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 ...
A delegate is a form of type-safe function pointer used by the Common Language Infrastructure (CLI). Delegates specify a method to call and optionally an object to call the method on. Delegates are used, among other things, to implement callbacks and event listeners. A delegate object encapsulates a reference to a method.
For instance, when the user clicks the close box, the window manager sends the delegate a windowShouldClose: call, and the delegate can delay the closing of the window, if there is unsaved data represented by the window's contents. Delegation can be characterized (and distinguished from forwarding) as late binding of self: [4]
CLI languages such as C# and VB.NET provide a type-safe encapsulating function reference known as delegate. Events and event handlers , as used in .NET languages, provide for callbacks. Functional languages generally support first-class functions , which can be passed as callbacks to other functions, stored as data or returned from functions.
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 ]
Like the Qt framework's pseudo-C++ signal and slot, C# has semantics specifically surrounding publish-subscribe style events, though C# uses delegates to do so. C# offers Java-like synchronized method calls, via the attribute [MethodImpl(MethodImplOptions.Synchronized)], and has support for mutually-exclusive locks via the keyword lock.
If an identifier is needed which would be the same as a reserved keyword, it may be prefixed by an at sign to distinguish it. For example, @out is interpreted as an identifier, whereas out as a keyword. This syntax facilitates reuse of .NET code written in other languages. [4] The following C# keywords are reserved words: [2]
The wrapper pattern, which resembles the delegates of C# in that it allows the client to access one or more client-defined methods through a known interface, is one such mechanism. [ citation needed ] Another is the use of adapter objects using inner classes, which the designers of Java argued are a better solution than bound method references.