DOCUMENT:Q194514  24-AUG-1999  [foxpro]
TITLE   :PRB: Cannot Pass Array Property of Form by Reference to OLE DLL
PRODUCT :Microsoft FoxPro
PROD/VER:WINDOWS:6.0
OPER/SYS:
KEYWORDS:kbCOMt kbvfp600

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-------------------------------------------------------------------------------
The information in this article applies to:

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

Trying to pass an array property of a form by reference to a COM server results
in the following error:

   "Alias 'THISFORM' is not found"

RESOLUTION
==========

There are two methods of working around this limitation:

1. Use the ACOPY() function to copy all the data from the array property to an
   array variable, then pass the array variable by reference.

   -or-

2. If having the array be a property is not a necessity, eliminate the array
   property, and dimension an array variable in the Init of the form. Pass that
   array by reference to the object.

   Example 1:

   Modify the btnOne.Click Method to the following:

            ***************Start Code Workaround 1****************
            PROCEDURE btnOne.CLICK
               THISFORM.oArrTest=CREATEOBJECT('frmArray.ArrTest')
               IF TYPE('thisform.oArrTest')#'O' then
                   WAIT WINDOW 'Did not instantiate'
                  RETURN
               ENDIF
               COMARRAY(thisform.oArrTest,11)
               ACOPY(THISFORM.MyArray,aTemp)
               THISFORM.oArrTest.modarray(@aTemp)
               DISPLAY MEMORY LIKE aTemp
            ENDPROC
            PROCEDURE btnClose.CLICK
               CLEAR EVENTS
               RELEASE THISFORM
            ENDPROC
            **********End Code Workaround 1********************

   Example 2:

   Replace the Client code with the following:

         ***************Start Code Workaround 2********************
         x=CREATEOBJECT("Test1")
         x.VISIBLE=.T.
         x.SHOW
         READ EVENTS

         DEFINE CLASS Test1 AS FORM OLEPUBLIC
            oArrTest=.NULL.
            ADD OBJECT btnOne AS COMMANDBUTTON WITH TOP = 1, ;
               CAPTION = 'Test Array'
            ADD OBJECT btnClose AS COMMANDBUTTON WITH TOP = 25, ;
               CAPTION = 'Close'
            PROCEDURE INIT
            DIMENSION aMyArray(5,1)
               I=1
               FOR I = 1 TO 5
                  aMyArray(I)='Form'
               ENDFOR
            ENDPROC

            PROCEDURE btnOne.CLICK
               THISFORM.oArrTest=CREATEOBJECT('frmArray.ArrTest')
               IF TYPE('thisform.oArrTest')#'O' then
                   WAIT WINDOW 'Did not instantiate'
                  RETURN
               ENDIF
               COMARRAY(thisform.oArrTest,11)
               THISFORM.oArrTest.modarray(@aMyArray)
               DISPLAY MEMORY LIKE aMyArray
            ENDPROC
            PROCEDURE btnClose.CLICK
               CLEAR EVENTS
               RELEASE THISFORM
            ENDPROC
         ENDDEFINE
         *************End Code Workaround 2*************************

STATUS
======

This behavior is by design.

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

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

1. Place the following Class Definition code in a program file attached to a
   project called frmArray:

         ****************Begin Class Definition*********
         DEFINE CLASS ArrTest AS CUSTOM OLEPUBLIC
            PROCEDURE modarray
               PARAMETERS MyArray
               EXTERNAL ARRAY MyArray
               FOR I = 1 TO 5
                  MyArray(I)="COM"
                ENDFOR
            ENDPROC
         ENDDEFINE
         **************End Class Definition************

2. Build the project into a COM DLL.

3. Place the following Client Code in a program file and run it:

         ***************Client Code Start*******************
         x=CREATEOBJECT("Test1")
         x.VISIBLE=.T.
         x.SHOW
         READ EVENTS

         DEFINE CLASS Test1 AS FORM OLEPUBLIC
            DIMENSION MyArray(5)
            oArrTest=.NULL.
            ADD OBJECT btnOne AS COMMANDBUTTON WITH TOP = 1, ;
               CAPTION = 'Test Array'
            ADD OBJECT btnClose AS COMMANDBUTTON WITH TOP = 25, ;
               CAPTION = 'Close'
            PROCEDURE INIT
               I=1
               FOR I = 1 TO 5
                  MyArray(I)='Form'
               ENDFOR
            ENDPROC

            PROCEDURE btnOne.CLICK
               THISFORM.oArrTest=CREATEOBJECT('frmArray.ArrTest')
               IF TYPE('thisform.oArrTest')#'O' then
                   WAIT WINDOW 'Did not instantiate'
                  RETURN
               ENDIF
               COMARRAY(thisform.oArrTest,11)
               THISFORM.oArrTest.modarray(@THISFORM.MyArray)
               DISPLAY MEMORY LIKE THISFORM.MyArray
            ENDPROC
            PROCEDURE btnClose.CLICK
               CLEAR EVENTS
               RELEASE THISFORM
            ENDPROC
         ENDDEFINE
         *****************Client Code End************************

4. When the form appears, press the "btnOne" button, and note the error message.

Additional query words: kbVFP600 kbComt

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Keywords          : kbCOMt kbvfp600 
Technology        : kbVFPsearch kbAudDeveloper kbVFP600
Version           : WINDOWS:6.0
Issue type        : kbprb

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