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Q129424: PRB: Property Not Evaluated When Object Is Created

Article: Q129424
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): kbcode
Last Modified: 12-FEB-2000

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The information in this article applies to:

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

The first time an instance of a class is created by using the CREATEOBJECT()
function, the properties of the class hold correct values. However, if a
property is based on an expression or a memory variable, it is not reevaluated
when another object is instantiated. The properties are not redefined from the
class definition once the class is in memory.

CAUSE
=====

The property is evaluated in the body of the class definition. The class values
are only evaluated the first time a class is loaded in memory. On the other
hand, properties that are modified in a method of a class are evaluated each
time the method is executed.

RESOLUTION
==========

If you want to evaluate a property based on an expression each time an object is
created, place the expression in the Init method, which is executed each time
the Init event takes place.

Sample Code
-----------

The following sample code demonstrates this method. In this example, two
properties are set. They evaluate the settings of SET TALK and SET EXACT. The
first property is set in a class definition. It is evaluated the first time the
class is loaded in memory. The value of the cSetExact property is set in the
Init event handler for this class. It is evaluated every time an object is
created.

     SET TALK ON
     SET EXACT OFF
     oObjenv = CREATEOBJECT('envircheck')
     RELEASE oObjenv

     SET TALK OFF
     SET EXACT ON
     oObjtest = CREATEOBJECT('envircheck')
     RELEASE oObjtest

     *: Class: envircheck  BaseClass: CUSTOM

     DEFINE CLASS envircheck AS CUSTOM

       mytalk = SET('talk')
       myexact = ""
      PROCEDURE INIT
         THIS.myexact = SET('exact')
         WAIT WINDOW "MYTALK is not reevaluated "+ THIS.mytalk
         WAIT WINDOW "MYEXACT is reevaluated "+ THIS.myexact
      ENDPROC

     ENDDEFINE

STATUS
======

This behavior is by design.

Additional query words: VFoxWin 3.00

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

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