Knowledge Base

PRB: "Property Not Found" Occurs When Running Form

Article ID: 129207

Article Last Modified on 8/3/2000

APPLIES TO

This article was previously published under Q129207

SYMPTOMS

The following error message displays while you are running a form:
Property Not Found

CAUSE

The period (.) operator was used in conjunction with macro substitution to reference a property that contains the name of an object. Because the compiler recognizes the period as the macro terminator, it doesn't evaluate the remainder of the line that contains the property.

WORKAROUND

To work around this problem, add an additional period after the macro substitution. The first period terminates the macro and the second allows the compiler to reference the property.

For example, to fix the problem, refer to the "Steps to Reproduce Behavior" section of this article, and replace the lines that use a single period to reference properties with the following lines of code: 
   This.&cOButton..Caption="Button"-cOldbNo && Originally used one period
   This.&cOButton..Picture=''

*** ...

   This.&cButton..Caption=""                && These lines are farther
   This.&cButton..Picture='c:\vfp\fox.bmp'  && down in the example
NOTE: Macro substitution can usually be replaced by the superior EVALUATE() function, but using EVALUATE() requires an additional line of code. In this example, program execution is faster and the amount of executable code generated by the compiler/linker is smaller. For example:

Instead of: 
   This.&cOButton..Picture=''
Use: 
   oRef=EVAL("THIS."+cOButton)
   oRef.Picture=''

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

The following program displays a form that contains three buttons (Button1, Button2, and Button3). Macro substitution is used to modify the Picture and Caption properties of these objects.
  1. From the File menu, choose New. Select the Program option, and then choose the New File button.
  2. Enter the following source code: 
       oMyForm = CREATEOBJECT("MyForm")
   oMyForm.show
   READ EVENTS

   DEFINE CLASS MyForm AS FORM
      nCurrentb=1

      ADD OBJECT Button1 AS COMMANDBUTTON WITH ;
        top=1,left=1,height=2,width=10,caption="",picture='c:\vfp\fox.bmp'

      ADD OBJECT Button2 AS COMMANDBUTTON WITH ;
        top=7,left=1,height=2,width=10

      ADD OBJECT Button3 AS COMMANDBUTTON WITH ;
        top=13,left=1,height=2,width=10

      PROCEDURE Button1.Click
        This.Parent.ChangeProp(1)
      ENDPROC

      PROCEDURE Button2.Click
        This.Parent.ChangeProp(2)
      ENDPROC

      PROCEDURE Button3.Click
        This.Parent.ChangeProp(3)
      ENDPROC

      PROCEDURE ChangeProp
         PARAMETERS nNewbutton

        cOldbNo=''
        cNewbNo=''
        cOButton=''
        cButton=''

         * Clear .bmp on old button
         cOldbNo=ALLTRIM(STR(This.nCurrentb))
         cOButton="Button"-cOldbNo
         This.&cOButton.Caption="Button"-cOldbNo  && WILL NOT WORK
         This.&cOButton.Picture=''                && WILL NOT WORK

         * Display .bmp on new button
         cNewbNo=ALLTRIM(STR(nNewbutton))
         cButton="Button"-cNewbNo
         This.&cButton.Caption=""                 && WILL NOT WORK
         This.&cButton.Picture='c:\vfp\fox.bmp'   && WILL NOT WORK

         This.nCurrentb=nNewbutton
      ENDPROC
   ENDDEFINE

Additional query words: VFoxWin 3.00 akz

Keywords: kberrmsg KB129207


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