KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q137443: Size and Nesting Level Limitations of Classes

Article: Q137443
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): 
Last Modified: 13-DEC-1999

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 3.0 
-------------------------------------------------------------------------------

SUMMARY
=======

Visual FoxPro 3.0 allows you to subclass any of the base classes provided by
Visual FoxPro. When subclassing, you are free to add your own properties and
methods to the predefined properties and methods for a base class. This article
explains some of the considerations in defining and using classes.

MORE INFORMATION
================

In general, there are no limits to the size of a class definition.
Theoretically, a class is capable of having four billion members (properties and
methods). However, every member definition does use a small amount of memory.
The amount of memory depends on the member name and member value.

Class nesting levels are limited by the following two factors:

- File handles: For each class that is subclassed, the file that contains the
  class definition must be opened. It is possible to combine class definitions
  in class files (.vcx or .prg files) to avoid running into this limitation.

- Stack space: When creating instances of objects that are either subclassed or
  contain objects that are subclassed, Visual FoxPro recursively reads in class
  definitions for subclasses. This can lead to an "Insufficient Stack Space"
  situation.

NOTE: As a general rule, well-designed applications should usually have no more
than five or six levels of subclassing.


Additional query words: VFoxWin

======================================================================
Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP300
Version           : WINDOWS:3.0

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.