explanation of aggregation, containment & delegation in com [closed]

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can u explain me what is the difference between aggregation, containment & delegation

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Since you've tagged this with COM, I'll assume you're asking how COM uses these terms - in COM terminology they mean something somewhat more specific than when used in general.

Conveniently, MSDN has pages that define these - I'll give a brief summary:

• Containment/Delegation - when one outer object owns (contains) and makes use of (delegates to) an inner object. The two objects maintain distinct identities and separate sets of interfaces.

• Aggregation - when two or more COM objects essentially pool their interfaces and behave as though they are a single COM object. The client code is then dealing with what appears to be a single object, but is in fact an 'aggregate' of other objects.

Aggregation is usually used when you want one object to 'inherit' a set of interfaces from another object. It's somewhat complex to implement, however: COM requires that from any interface on an object you must be able to QI to any other interface, so the various objects involved have to cooperate to ensure that you can QI from any interface on one of the objects to any interface on the other, an have ref counting work across both objects.

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Containment describes the idea of one class, having a data member that is an object of another class/type.

Delegation expresses the idea that one class uses another class to accomplish a task or goal.

Delegation is usually accomplished by containment

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Aggregation and Containment are generic concepts (concepts above com or any other technology) of Object Composition. The Object Composition link, has a separate section on Aggregation in com also.

Similarly, you can read about delegation.