Knowledge Base

FIX: Inherited Code Fires Twice with DODEFAULT()

Article ID: 158250

Article Last Modified on 12/11/1999

APPLIES TO

This article was previously published under Q158250

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.

Keywords: kbbug kbfix kbvfp500afix kbprogramming KB158250


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