Article: Q130834
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s):
Keyword(s): kbcode
Last Modified: 15-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
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By default, parameters are passed by value to user-defined functions and by
reference to procedures called with a DO command. This article explains how an
Object-type variable is passed as a parameter.
MORE INFORMATION
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Object variables are always passed by reference to user-defined functions and
procedures. Creating an object creates a reference to an object of a class. When
a procedure or a method receives an object as a parameter, any change made to
the parameter affects the object. Only one instance of the object actually
exists; the parameter points to the same object as the instance variable.
To pass an Object reference from a form, you can use this syntax:
Thisform.mymethod(this)
-or-
Thisform.mymethod
In the following example code, a form is created, and the ChangeCaption method of
the form is called. Controls are passed as parameters. This example could have
been programmed differently by making the ChangeCaption a method of any control.
It is included to illustrate how object type variables are passed as
parameters.
Sample code
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PUBLIC oForm
oForm=CREATEOBJECT('Myform')
oForm.show
=MESSAGEBOX('Note the Caption of the CommandButton')
oForm.ChangeCaption(oform.mycmd)
=MESSAGEBOX('Note the Caption of the CommandButton')
DEFINE CLASS myform as FORM
ADD OBJECT mycmd as COMMANDBUTTON with Caption = "Before"
ADD OBJECT cmdquit1 as cmdquit
PROCEDURE ChangeCaption
PARAMETER objref
objref.Caption="After"
ENDPROC
ENDDEFINE
DEFINE CLASS cmdquit as COMMANDBUTTON
Caption= "Quit"
Top=25
Left=25
PROCEDURE Click
RELEASE Thisform
ENDPROC
ENDDEFINE
Additional query words: VFoxWin
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Keywords : kbcode
Technology : kbVFPsearch kbAudDeveloper kbVFP300
Version : WINDOWS:3.0
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