Automatic Object Interfaces

Each of the CML application's COM components implements one interface that provides its CML-specific functionality. Invariably, the interface has the same name as the component. For example, the UserInfo component exposes methods used by the CML through its UserInfo interface.

In addition, to be COM-compliant, these components expose the following two interfaces:

• IUnknown. When present on a given object, this interface supplies pointers to other interfaces on that object through the QueryInterface method. It also manages the existence of the object through reference counting, using the AddRef and Release methods. All other COM interfaces are inherited from IUnknown.
• IDispatch. The four methods of this interface provide a way to expose properties, methods, and entire objects. This helps enable Automation, for example. This interface is also often used to enable C/C++ applications and Microsoft Visual Basic applications to work together.

Finally, all of these components have a set of interfaces automatically added when the object is compiled in Microsoft Visual Basic, including:

• _Dclass
• IConnectionPoint
• IConnectionPointContainer
• IExternalConnection
• IProvideClassInfo
• ISupportErrorInfo

For more information about this group of interfaces, refer to the topics on COM and ActiveX object services in the Microsoft Platform SDK on the Microsoft Developer Network (MSDN™). None of these interfaces are used directly by the CML application.