PRB: ControlSource Variables not Visible until Text Box Selected
ID: Q196086
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The information in this article applies to:
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Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a, 6.0
SYMPTOMS
If you base the ControlSource of a text box on a private or local memory
variable and is the text box is populated before the form runs, then the
variable is not visible to the methods or events of the form and its
components until you select the text box by either clicking the text box or
tabbing to the text box.
CAUSE
When the form is first instantiated, the memvars are still in scope. After
the form has fully instantiated, the .prg file continues and ends,
releasing the memvars. You can still see the values in the text boxes
because the values were read before the memvars went out of scope. When you
click the text box, it tries to refresh from the Controlsource. However,
the Controlsource memvar does not exist, so the text box creates the
memvar, and stores the current text box value in that memvar.
RESOLUTION
Following are two workarounds:
- Place a READ EVENTS after calling the form as follows:
CLEAR ALL
USE MyTbl
SELECT MyTbl
SCATTER MEMVAR
DO FORM MyFrm
READ EVENTS
-or-
- Declare the memory variable as public.
STATUS
This behavior is by design.
MORE INFORMATIONSteps to Reproduce Behavior
- Create and populate a table as follows:
CREATE TABLE MyTbl (Fld1 C(2), Fld2 n(2), Fld3 n(2), Fld4 n(2))
INSERT INTO MyTbl Values ("aa",1,1,1)
INSERT INTO MyTbl Values ("bb",2,2,2)
- Create a form, MyFrm, and add a command button to it with the following
code in the Click event:
M.Fld4 = M.Fld2 + M.Fld3
- Add four (4) text boxes Text1, Text2, Text3, and Text4 to the form. Set
the ControlSource for each of the text box controls to M.Fld1, M.Fld2,
M.Fld3, and M.Fld4 respectively. Save the form.
- Create a program file (.prg) with the following code:
CLEAR ALL
USE MyTbl
SELECT MyTbl
SCATTER MEMVAR
DO FORM MyFrm
- Run the program created in step 4.
- When the form opens, note that all the values for the text boxes display
correctly.
- Click the command button, and you the following error occurs:
Variable Fld2 is not found.
- Select Ignore and then close the form.
- Repeat step 5 and click Text2 when the form opens. Clicking the command
button does not produce any errors for Fdl2 but you now get this error:
Variable Fld3 is not found.
- Select ignore and close the form.
- Repeat step 5. When the form displays, click Text2 and then click
Text3. Now, clicking the command button does not produce the error(s).
Additional query words:
Keywords : kbContainer kbCtrl kbVFp300b kbVFp500 kbVFp500a kbVFp600
Version : WINDOWS:3.0,3.0b,5.0,5.0a,6.0
Platform : WINDOWS
Issue type : kbprb
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