Used between the BEGIN_INTERFACE_MAP macro and the END_INTERFACE_MAP macro for each interface your object will support.
INTERFACE_PART(theClass, iid, localClass)
The name of the class that contains the interface map.
The IID that is to be mapped to the embedded class.
The name of the local class.
It allows you to map an IID to a member of the class indicated by theClass and localClass.
For more information on interface maps, see Technical Note 38.