Chapter 3: The Component Object Model

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Objectives:

• Understand the benefits of the COM architecture.

• Give your objects identity with IUnknown.

• Develop COM interfaces, coclasses, and component housing.

• Learn to manipulate string data in COM.

• Understand COM class factories and IClassFactory.

• Develop COM clients using the COM library.

• Learn how to debug COM-based DLLs.

Microsoft's Component Object Model (COM) takes what you already know about objects and interfaces and extends them into the binary arena. Thus, everything you have read up to this point has prepared you to develop and use "real COM" components. In this chapter, you will learn exactly what the COM architecture is and the many benefits it provides. Next, you will have the chance to build an in-process COM server from the ground up using 100% straight C++. While you might see this as a slightly painstaking endeavor, it will provide a solid foundation for understanding ATL. Finally, you will learn about the various COM runtime services (the COM library, the service control manager, and the system registry) that provide the necessary run-time environment to create COM clients.

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