PRB: Cannot Pass an Array Member to a Procedure (130224)
The information in this article applies to:
- Microsoft Visual FoxPro for Windows 3.0
This article was previously published under Q130224 SYMPTOMS
An array that is declared as a member of a class cannot be passed by
reference to a function or a method. For example, if you declare an array
as a property of a form, the error "Alias 'this' is not found" is displayed
when a method is called as follows:
This.pNewFunction(@this.atest)
CAUSE
Visual FoxPro always passes object properties by value. Object properties
cannot be passed by reference.
WORKAROUND
An alternative is to pass the array name to a method, and manipulate the
array or a copy of the array. The following example code defines a form
with a command button. When the command button is clicked, a function is
called that adds 10 to each element of an array declared as a property of
the command button. The same method can be used in the Form Designer.
Sample Code
PUBLIC oform
oform=CREATEOBJECT('frmtest')
oform.Show
DEFINE CLASS frmtest AS FORM
ADD OBJECT cmd1 AS cmd
ENDDEFINE
DEFINE CLASS cmd AS COMMANDBUTTON
DIMENSION aprop[10]
PROCEDURE init
LOCAL ii
FOR ii = 1 TO 10
This.aprop[ii]=ii
ENDFOR
ENDPROC
PROCEDURE click
LOCAL ii
THIS.ADDEM(This, 'aprop')
ACTIVATE SCREEN
FOR ii =1 TO 10
?This.aprop[ii]
ENDFOR
ENDPROC
* Two parameters are passed to the procedure: a reference to the object,
* and the array name.
PROCEDURE ADDEM
LPARAMETERS oref, cprop
local ii, atemp[1]
=ACOPY(oref.&cprop,atemp) & Makes a copy of the member array.
FOR ii = 1 TO aLEN(oref.&cprop)
atemp[ii]=atemp[ii] + 10
ENDFOR
=ACOPY(atemp,oref.&cprop)
ENDPROC
ENDDEFINE
STATUS
This behavior is by design.
| Modification Type: | Major | Last Reviewed: | 2/10/2000 |
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| Keywords: | kbcode KB130224 |
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