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Run Time Class Handler: Instantiating Classes by Name


This article was contributed by Ernst Versteeg.

Environment: Win16 (VC++ 1.52) and Win9x/NT (VC++ 6.0)

With this class I was able to simply add a file with a new class to my project and to instantiate new objects from this class simply by altering or adding the name of the class in the database or in configuration files.  This way I didn't need to add code for the support of the added class to existing code or to register the class with class factories.

So this is VERY useful if you like to disconnect classes from each other on compile level or to avoid making special class factories.

This class is tested and is in use for both 16/32 bit versions.

Notes:

  1. Use DECLARE_SERIAL and the IMPLEMENT_SERIAL macro for classes which should be used for this function.

  2. As with all classes which use DECLARE_SERIAL a default empty constructor is needed.  If you need initialization, a "Create" function be made and used after a cast of the returned object to the appropriate class.

  3. DECLARE_DYNCREATE does not work with the 32 bit part of this code, perhaps somebody knows why.

  4. As far as I know, this way of coding is part of SmallTalk.

Downloads

Download source - 2 Kb

History

Date Posted: May 29, 1999
Date Last Updated: December 17, 1999

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