Specifies that your object must be aggregated.
[in] The name of the class object you are defining as only aggregatable.
DECLARE_ONLY_AGGREGATABLE causes an error (E_FAIL) if an attempt is made to CoCreate your object as nonaggregated object.
By default, CComCoClass contains the DECLARE_AGGREGATABLE macro, which specifies that your object can be aggregated. To override this default behavior, include DECLARE_ONLY_AGGREGATABLE in your class definition.