Q158250: FIX: Inherited Code Fires Twice with DODEFAULT()

Article: Q158250
Product(s): Microsoft FoxPro
Version(s): WINDOWS:5.0
Operating System(s): 
Keyword(s): kbprogramming kbvfp kbvfp500aFIXkbbuglist kbfixlist
Last Modified: 11-DEC-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 5.0 
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SYMPTOMS
========

When the DODEFAULT() function is used in a subclass method, it executes a method
in the parent with the same name. When the parent has no method with that name,
it then looks to the grandparent for that method. If it exists, it is executed.
If the grandparent has a NODEFAULT() function, the code gets executed twice.

CAUSE
=====

The parent in the above situation executes the code of the grandparent as its
own. Because the grandparent has a NODEFAULT() function, the parent calls the
method of the grandparent again.

WORKAROUND
==========

To work around this problem, place a method that has the same name in the
parent. Place a DODEFAULT() command in the parent method.

STATUS
======

This behavior is by design in the products listed at the beginning of this
article. This behavior does not occur in Visual FoxPro 5.0a

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

Steps to Reproduce Behavior
---------------------------

1. Create a program with the following code:

        ACTIVATE SCREEN
        CLEAR
        CREATEOBJECT("Test3")
        RETURN

        DEFINE CLASS Test AS Form
        ENDDEFINE

        DEFINE CLASS test1 AS Test
           PROCEDURE Load
              ACTIVATE SCREEN
              ? "Class Test1, this.Class="+this.Class+ ;
                ", this.ParentClass="+this.ParentClass
                 DODEFAULT()
           ENDPROC
        ENDDEFINE

        DEFINE CLASS test2 AS test1
        ENDDEFINE

        DEFINE CLASS test3 AS test2
           PROCEDURE Load
              ACTIVATE SCREEN
              ? "Class Test3, this.Class="+this.Class+ ;
                ", this.ParentClass="+this.ParentClass
              DODEFAULT()
           ENDPROC
        ENDDEFINE

2. Run the code. The Load method of test1 prints twice.

Change Class test2 in the following way if you wish the code in test1 to execute
only once:

        DEFINE CLASS test2 AS test1
          PROCEDURE Load
             DODEFAULT()
          ENDPROC
        ENDDEFINE

The above code prevents Class test2 from running class test1's code as its own.

Additional query words:

======================================================================
Keywords          : kbprogramming kbvfp kbvfp500aFIX kbbuglist kbfixlist
Technology        : kbVFPsearch kbAudDeveloper kbVFP500
Version           : WINDOWS:5.0
Issue type        : kbbug
Solution Type     : kbfix

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