IUnknown::QueryInterface

Determines whether the object supports a particular COM interface. If it does, the system increases the object's reference count, and the application can use that interface immediately.

HRESULT QueryInterface(
  REFIID riid,
  LPVOID * ppvObj
);

Parameters

riid

Reference identifier of the interface being requested.

ppvObj

Address of a pointer to fill with the interface pointer if the query succeeds.

Return Values

If the method succeeds, the return value is S_OK.

If the method fails, the return value may be E_NOINTERFACE. Some components also have their own definitions of these error values in their header files.

Remarks

If the application does not need to use the interface retrieved by a call to this method, it must call the IUnknown::Release method for that interface to free it. The IUnknown::QueryInterface method makes it possible to extend objects without interfering with functionality.

Requirements

Header: Declared in Unknwn.h.