OLE Custom Interfaces
As an OLE developer, you implement and use objects that are based on the
Component Object Model (COM). COM interfaces specify a contract between the
interface implementor and its user. The contract applies to every COM object that
supports that interface.
OLE provides a standard set of interfaces, but these OLE-provided interfaces
may not be perfectly suited to your needs. Through custom interfaces, you can
create new ones tailored to fulfill the specific needs of your application.
Custom interfaces are extensions to the COM standard; they let you extend the
standard behavior and still take advantage of the services provided by the base
interface. Like all COM interfaces, custom interfaces derive from the IUnknown
interface and must contain the three methods of IUnknown
. Otherwise, they can support a wide range of methods and parameters. (Note
that, currently, custom interfaces cannot include asynchronous methods.
Asynchronous methods may be supported in future versions of OLE.)
Once the interface is written, anyone can use it. Calls to methods in COM
interfaces can cross process boundaries as long as both processes are running on
the same machine.
This appendix introduces custom interfaces and explains how to implement them.
OLE experience is a prerequisite, as is a basic knowledge of RPC. For more
information about OLE and COM technology, see the OLE Reference Guide
and the other parts of this OLE Programmer's Guide
. Refer to the RPC Programmer's Guide and Reference
for information about the RPC programming environment.
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