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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]
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.
In computing or computer programming, delegation refers generally to one entity passing something to another entity, [1] and narrowly to various specific forms of relationships. These include: Delegation (object-oriented programming), evaluating a member of one object (the receiver) in the context of another, original object (the sender).
The class types are user-defined classes, boxed value types, and delegates. The following example written in Visual Basic .NET shows the difference between reference types and value types: Imports System Class Class1 Public Value As Integer = 0 End Class 'Class1 Class Test Shared Sub Main () Dim val1 As Integer = 0 Dim val2 As Integer = val1 ...
These are anonymous methods: they have a signature and a body, but no name. They are mainly used to specify local function-valued arguments in calls to other methods, a technique mainly associated with functional programming. C#, unlike Java, allows the use of lambda functions as a way to define special data structures called expression trees.
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.
The next program uses a function pointer to invoke one of two functions (sin or cos) indirectly from another function (compute_sum, computing an approximation of the function's Riemann integration). The program operates by having function main call function compute_sum twice, passing it a pointer to the library function sin the first time, and ...