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IDispatchImpl Class
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IDispatchImpl Class

Provides a default implementation for the IDispatch part of a dual interface.

Important note Important

This class and its members cannot be used in applications that execute in the Windows Runtime.

   class T,
   const IID* piid= &__uuidof(T),
   const GUID* plibid = &CAtlModule::m_libid,
   WORD wMajor = 1,
   WORD wMinor = 0,
   class tihclass = CComTypeInfoHolder 
class ATL_NO_VTABLE IDispatchImpl :
   public T

[in] T

A dual interface.

[in] piid

A pointer to the IID of T.

[in] plibid

A pointer to the LIBID of the type library that contains information about the interface. By default, the server-level type library is passed.

[in] wMajor

The major version of the type library. By default, the value is 1.

[in] wMinor

The minor version of the type library. By default, the value is 0.

[in] tihclass

The class used to manage the type information for T. By default, the value is CComTypeInfoHolder.




The constructor. Calls AddRef on the protected member variable that manages the type information for the dual interface. The destructor calls Release.




Maps a set of names to a corresponding set of dispatch identifiers.


Retrieves the type information for the dual interface.


Determines whether there is type information available for the dual interface.


Provides access to the methods and properties exposed by the dual interface.

IDispatchImpl provides a default implementation for the IDispatch part of any dual interface on an object. A dual interface derives from IDispatch and uses only Automation-compatible types. Like a dispinterface, a dual interface supports early binding and late binding; however, a dual interface also supports vtable binding.

The following example shows a typical implementation of IDispatchImpl.

class ATL_NO_VTABLE CBeeper :
   public CComObjectRootEx<CComSingleThreadModel>,
   public CComCoClass<CBeeper, &CLSID_Beeper>,
   public IDispatchImpl<IBeeper, &IID_IBeeper, &LIBID_NVC_ATL_COMLib, /*wMajor =*/ 1, /*wMinor =*/ 0>

By default, the IDispatchImpl class looks up the type information for T in the registry. To implement an unregistered interface, you can use the IDispatchImpl class without accessing the registry by using a predefined version number. If you create an IDispatchImpl object that has 0xFFFF as the value for wMajor and 0xFFFF as the value for wMinor, the IDispatchImpl class retrieves the type library from the .dll file instead of the registry.

IDispatchImpl contains a static member of type CComTypeInfoHolder that manages the type information for the dual interface. If you have multiple objects that implement the same dual interface, only one instance of CComTypeInfoHolder is used.

Header: atlcom.h

© 2015 Microsoft