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Q130460: Using a Variable as a Parameter for CreateObject()

Article: Q130460
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): kbcode
Last Modified: 11-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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SUMMARY
=======

CreateObject() takes a classname as a parameter. This article shows by example
how to set a variable equal to the classname, and than use that variable as the
parameter for every CreateObject() function for that class. Should the class
later be subclassed, you only need to change the variable name from the old
classname to the new subclass name; only a single line of code had to change.

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

The following program, which does not use the variable to hold the classname,
creates three blank forms with a white backcolor. The program also defines
GreyForm as a subclass of Form. It has its backcolor set to grey. To base each
form off of the GreyForm class instead of the Form class, requires that each
occurrence of createObject('Form') be replaced with CreateObject('GreyForm').

  x=CreateObject('Form')
  y=CreateObject('Form')
  z=CreateObject('Form')
  x.visible=.T.
  y.visible=.T.
  z.visible=.T.

  DEFINE CLASS GreyForm as Form
     BackColor=RGB(192,192,192)
     Caption="Grey"
  ENDDEFINE

The following program is identical in function to the first one. However, it uses
a variable to hold the classname. Now you need only change the first line to
cForm="GreyForm" to base all of the forms off of the GreyForm subclass.

  cForm="Form"
  x=CreateObject(cForm)
  y=CreateObject(cForm)
  z=CreateObject(cForm)
  x.visible=.T.
  y.visible=.T.
  z.visible=.T.

  DEFINE CLASS GreyForm as Form
     BackColor=RGB(192,192,192)
     Caption="Grey"
  ENDDEFINE

Additional query words: VFoxWin KBfest

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

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