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Q190789: PRB: Access Method Fires for Properties that Do Not Exist

Article: Q190789
Product(s): Microsoft FoxPro
Version(s): WINDOWS:6.0
Operating System(s): 
Keyword(s): 
Last Modified: 11-DEC-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 6.0 
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SYMPTOMS
========

Accessing a property that does not exist in a class still fires the Access
method.

CAUSE
=====

This behavior permits the design of classes that support the addition of custom
properties at run-time using the AddProperty method. For example, the following
class definition adds a new property to the class at run-time when a
non-existent property is accessed:

     x = NewObject("myclass")

     ?x.NewProp  && New Property will be added to class.

     ?x.NewProp  && Note new property value.

     x.NewProp="Hello"  && Value assigned since property already exists.

     ?x.newprop

     DEFINE Class myclass as Custom
        PROCEDURE this_access(tcMember)
           IF ! PEMStatus(this,tcMember,5)
              this.AddProperty(tcMember)
           ENDIF
           RETURN this
        ENDPROC
     ENDDEFINE

STATUS
======

This behavior is by design.

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

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

Run the following code:

     x = NewObject('myclass')
     ?x.BogusProperty

     DEFINE class myclass as custom
        PROCEDURE this_access(tcMember)
           WAIT WINDOW tcMember
           RETURN this
        ENDPROC
     ENDDEFINE

The Access method fires before you receive the invalid property error.

Additional query words: kbVFp600 kbOOP

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP600
Version           : WINDOWS:6.0
Issue type        : kbprb

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