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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]
Before one can use the members of the class, initialize the variable with a reference to an object. To create it, call the appropriate constructor using the new keyword. It has the same name as the class.
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.
In practice, the available CLASS words would be a list of less than two dozen terms. CLASS words, typically positioned on the right (suffix), served much the same purpose as Hungarian notation prefixes. The purpose of CLASS words, in addition to consistency, was to specify to the programmer the data type of a particular data field. Prior to the ...
CLI languages such as C# and Visual Basic .NET implement type-safe function pointers with delegates. In other languages that support first-class functions, functions are regarded as data, and can be passed, returned, and created dynamically directly by other functions, eliminating the need for function pointers.
The observer design pattern is a behavioural pattern listed among the 23 well-known "Gang of Four" design patterns that address recurring design challenges in order to design flexible and reusable object-oriented software, yielding objects that are easier to implement, change, test and reuse.
In class-based programming, methods are defined within a class, and objects are instances of a given class. One of the most important capabilities that a method provides is method overriding - the same name (e.g., area) can be used for multiple different kinds of classes. This allows the sending objects to invoke behaviors and to delegate the ...