Q129159: How to Fill an Array Used as the Rowsource of a Combo Box
Article: Q129159
Product(s): Microsoft FoxPro
Version(s): 3.00
Operating System(s):
Keyword(s): kbcode
Last Modified: 21-AUG-1999
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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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When you define a list or combo box from an array, you should first declare the
array as a property of the form. This causes the array to be visible to the form
object, so the list or combo box can access it. You can then populate the array
within one of the methods of the form. This article describes two techniques
that can be used to populate the array and view its elements in a list box or a
combo box.
MORE INFORMATION
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In the Form Designer, you can declare an array as a property of a form by
choosing Form New Property from the System Menu. For more information about
declaring and referencing the array declared as a member of a form, please see
the following article in the Microsoft Knowledge Base:
Q128737 How to Declare Arrays on Forms
When a list box or combo box is initialized, it lists its elements from the
source specified with the RowSource and RowSourceType properties. The number of
elements displayed in the list is evaluated at definition time. If the
RowSourceType is 5-Array, and if the array is not dimensioned at the time the
list is defined, only one element will show. The number of elements displayed in
the list is not automatically evaluated when a change is made to the array.
Therefore, if the array is populated after the control is initialized, the
number of elements in the list has to be reevaluated.
Following are two methods you can use to populate an array used as the rowsource
of a list box. They ensure that all of the elements of the array are visible,
even when it is populated after the list box control has been initialized.
Method One: Fill the Array in the Load Event Handler
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The Load event of a form is executed before the objects are initialized. When the
list or combo box controls are initialized, the array contains elements and the
NUMBEROFELEMENTS property of the list box is calculated to accommodate all of
the elements of the list. Here's an example:
1. Declare the array atest(5) from the Form, New Property menu.
2. In the method for the LOAD event of the form, type:
SELECT Cust_ID FROM SYS(2004)+"SAMPLES\DATA\CUSTOMER";
INTO ARRAY thisform.atest
3. Place a Combo box on the form, and modify the following properties:
RowSourceType=5-Array
Rowsource='Thisform.atest'
4. Save and run the Form. The list displays 90 elements.
Method Two: Populate the Array in the Init Event Handler
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It is possible to place the code that initializes the array in the Init event
handler of the control or the Init of the Form. However, in both cases, the
array is filled after the number of elements for the list has been set. Because
it is not dynamically evaluated, it is necessary to reevaluate the number of
elements of the list to size it appropriately.
Use the REQUERY method to re-query the source of the combo box. It will adjust
the number of elements displayed in the list. You can also manually set the
number of elements of the list by setting the NumberOfElements property of the
list. The following example illustrates this behavior. To run the example, copy
and paste the code in a program file. When the form is displayed, the list shows
only one element. Click the Fill the list button to view the elements of the
array in the list.
ofrm1 = CREATEOBJECT('frm1')
ofrm1.show
READ EVENTS
***********************
** Class definitions **
***********************
DEFINE CLASS frm1 AS form
DIMENSION ATEST(1)
ADD OBJECT lsttest AS lstarray
ADD OBJECT cmdtest AS cmdquit
ADD OBJECT cmdquery AS cmdrequery
Caption = "Press the Button to See Elements in List"
PROCEDURE INIT
* Fills the array that is the source of the list box
DIMENSION this.atest(4)
THIS.ATEST(1)="Apples"
THIS.ATEST(2)="Oranges"
THIS.ATEST(3)="Peach"
THIS.ATEST(4)="Kiwi"
ENDPROC
ENDDEFINE
DEFINE CLASS lstarray AS listbox
Height = 85
Left = 84
Top = 60
* Defines the list as a list from an array
PROCEDURE INIT
This.RowSource = 'THIS.PARENT.Atest'
This.RowSourceType =5
ENDPROC
ENDDEFINE
DEFINE CLASS cmdquit AS Commandbutton
Top=150
Left=49
Caption= "Quit"
PROCEDURE click
RELEASE Thisform
CLEAR EVENTS
ENDDEFINE
DEFINE CLASS cmdrequery as COMMANDBUTTON
Top=150
Left=144
Caption= "Fill the list"
* The Click method goes through the controls of the form and refreshes
* the list.
PROCEDURE Click
NumberofControls=This.parent.controlcount
FOR I=1 to numberofcontrols
IF this.parent.controls(i).BaseClass="Listbox"
THIS.PARENT.controls(i).Requery
ENDIF
ENDFOR
THISFORM.REFRESH
ENDPROC
ENDDEFINE
NOTE: You can use the REQUERY method to refresh a list or a combo box when the
underlying data source is modified.
Additional query words: VFoxWin
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Keywords : kbcode
Technology : kbVFPsearch kbAudDeveloper kbVFP300
Version : 3.00
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