Visual C++ 6 Unleashed

By MICKEY WILLIAMS and David Bennett

• Table of Contents
  • Copyright
  • About the Authors
  • About the Contributors
  • Acknowledgments
  • Tell Us What You Think!
  • Introduction
  • How to Use This Book
  • What You Need to Use This Book
  • What's New in Visual C++ 6.0
  • Contacting the Main Author
  • Part I: Introduction
  • Chapter 1. The Visual C++ 6.0 Environment
  • Part II: MFC Programming
  • Chapter 2. MFC Class Library Overview
    • The Application Framework
    • Creating an MFC Application with MFC AppWizard
    • The CWinApp Class
    • The CWinThread Class
    • The CCmdTarget Class
    • The CObject Class
    • Runtime Type Information
    • Debugging Support
    • Putting It All Together
    • The Message Pump
    • Summary
  • Chapter 3. MFC Message Handling Mechanism
  • Chapter 4. The Document View Architecture
  • Chapter 5. Creating and Using Dialog Boxes
  • Chapter 6. Working with Device Contexts and GDI Objects
  • Chapter 7. Creating and Using Property Sheets
  • Chapter 8. Working with the File System
  • Chapter 9. Using Serialization with File and Archive Objects
  • Part III: Internet Programming with MFC
  • Chapter 10. MFC and the Internet Server API (ISAPI)
  • Chapter 11. The WinInet API
  • Chapter 12. MFC HTML Support
  • Part IV: Advanced Programming Topics
  • Chapter 13. Using the Standard C++ Library
  • Chapter 14. Error Detection and Exception Handling Techniques
  • Chapter 15. Debugging and Profiling Strategies
  • Chapter 16. Multithreading
  • Chapter 17. Using Scripting and Other Tools to Automate the Visual C++ IDE
  • Part V: Database Programming
  • Chapter 18. Creating Custom AppWizards
  • Chapter 19. Database Overview
  • Chapter 20. ODBC Programming
  • Chapter 21. MFC Database Classes
  • Chapter 22. Using OLE DB
  • Chapter 23. Programming with ADO
  • Part VI: MFC Support for COM and ActiveX
  • Chapter 24. Overview of COM and Active Technologies
  • Chapter 25. Active Documents
  • Chapter 26. Active Containers
  • Chapter 27. Active Servers
  • Chapter 28. ActiveX Controls
  • Part VII: Using the Active Template Library
  • Chapter 29. ATL Architecture
  • Chapter 30. Creating COM Objects Using ATL
  • Chapter 31. Creating ActiveX Controls Using ATL
  • Chapter 32. Using ATL to Create MTS and COM+ Components
  • Part VIII: Finishing Touches
  • Chapter 33. Adding Windows Help
  • Part IX: Appendix

The CCmdTarget Class

All window classes under MFC that accept user input, including OLE classes, are derived at some level from CCmdTarget. This class is used as a base class for so many other classes because it allows your class to handle Windows messages.

Windows programs are based on an event-driven model. This means that they run in the traditional sense for only a short time at startup, then spend the rest of their lives waiting around for messages, reacting to them, and waiting again for more messages. These messages can be generated by simply moving the mouse, clicking on a button, or selecting a menu command.

In C programs, these messages were generally handled by large switch blocks involving case statements for each message that your application wanted to process. Because the processing of these messages was often dependent on several other variables, most applications ended up with a massive web of nested switch and if blocks.

To remedy this situation, and to allow you to use the power of C++ freely, MFC has implemented message maps to allow your classes to handle Windows messages in a much cleaner fashion. Any class derived from CCmdTarget may have its own message map, allowing each class to handle the messages it is interested in however it chooses, while leaving other messages to be handled higher in the class hierarchy.

Working with messages is one of the most important things that you will do in Windows programming (so important that it has its own chapter—Chapter 3, "MFC Message Handling Mechanism" ). For now, let's move on to the base class of CCmdTarget , CObject .

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