interface lets clients get pointers to other interfaces on a given object
through the QueryInterface
method, and manage the existence of the object through the IUnknown::AddRef
methods. All other COM interfaces are inherited, directly or indirectly, from IUnknown
. Therefore, the three methods in IUnknown
are the first entries in the VTable for every interface.
When to Implement
You must implement IUnknown
as part of every interface. If you are using C++ multiple inheritance to
implement multiple interfaces, the various interfaces can share one implementation
. If you are using nested classes to implement multiple interfaces, you must
once for each interface you implement.
When to Use
methods to switch between interfaces on an object, add references, and
Methods in Vtable Order
||Returns pointers to supported interfaces.
||Increments reference count.
||Decrements reference count.
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