HOWTO: Use the _arraylib Class from _utility Class Library

ID: Q186084

The information in this article applies to:

Microsoft Visual FoxPro for Windows, version 6.0

SUMMARY

Inserting data into or removing data from an array can become a rather tedious programming task. Visual FoxPro 6.0 provides the _arraylib class in the _utility.vcx class library to facilitate inserting data into and removing data elements from arrays. The purpose of this article is to demonstrate use of the _arraylib class.

MORE INFORMATION

The _arraylib class, included in the _utility.vcx class library, provides two functions for inserting data into and removing data from arrays. The insaitem method allows insertion of data into an array while the delaitem method allows deletion of an element from an array. In both cases, the name of the array is passed, by reference, to the method. The exact syntax is dependent on the method being called and how the method is used.

You can use the delaitem method to delete a single array element or an entire row from a multi-dimensional array. The parameters accepted by the delaitem method are:


   aArray    - The name of the array.
   wziRow    - Parameter for the row to be deleted from the array.

The name of the array and the row to delete are required parameters.

Calls to the delaitem method use the following syntax:

THISFORM._arraylib1.delaitem(@array_name,array_row)

You use the insaitem method to insert data elements into an array. The parameters accepted by the insaitem method are:


   aArray    - The name of the array.
   sContents - Contents to insert into the array.
   iRow      - Optional parameter for the row to insert into.
   lSetAll   - Optional parameter for propagating the contents passed in
               sContents to all columns of the newly inserted row of the
               array.

The name of the array and the value to insert are required parameters. You may pass an optional numeric value in the parameter list indicating in which row to insert the array element. The insaitem method also accepts an optional logical parameter indicating whether or not the value passed in sContents is in all row elements of a multi-dimensional array. Calls to the insaitem method use the following syntax:

THISFORM._arraylib1.insaitem(@array_name,array_element[,[irow], [lsetall]])

The code sample below illustrates use of the _arraylib class.

Create a program file called Arraylib.prg using the following code:


      CLOSE ALL
      SET CLASSLIB TO HOME()+"FFC\_UTILITY.VCX"
      outilobject=CREATEOBJECT('array_form')
      outilobject.SHOW
      READ EVENTS

      DEFINE CLASS array_form AS FORM
         TOP = 0
         LEFT = 0
         HEIGHT = 180
         WIDTH = 220
         DOCREATE = .T.
         CAPTION = "_Utilities Demonstration"
         NAME = "ARRAY_FORM"
         AUTOCENTER=.T.

         ADD OBJECT list1 AS LISTBOX WITH ;
            HEIGHT = 125, ;
            LEFT=05, ;
            TOP = 10, ;
            WIDTH = 100, ;
            ROWSOURCETYPE=5, ;
            ROWSOURCE="arraya"

         ADD OBJECT list2 AS LISTBOX WITH ;
            HEIGHT = 125, ;
            LEFT=115, ;
            TOP = 10, ;
            WIDTH = 100, ;
            ROWSOURCETYPE=5, ;
            ROWSOURCE="arrayb"

         ADD OBJECT command2 AS COMMANDBUTTON WITH ;
            LEFT=10, ;
            HEIGHT=25, ;
            CAPTION="Close Form", ;
            TOP=150, ;
            WIDTH=200, ;
            NAME = "Command2"

         ADD OBJECT _arraylib1 AS _arraylib

         PROCEDURE LOAD
            PUBLIC arraya, arrayb
            DECLARE arraya[4]
            arraya[1]="Apple"
            arraya[2]="Banana"
            arraya[3]="Orange"
            arraya[4]="Pear"
            DECLARE arrayb[4]
            arrayb[1]="Blueberry"
            arrayb[2]="Cherry"
            arrayb[3]="Grapefruit"
            arrayb[4]="Strawberry"
         ENDPROC

         PROCEDURE list1.CLICK
            LOCAL thisval
            thisval=THISFORM.list1.VALUE
            stringval=arraya[thisval]
            FOR i=1 TO ALEN(arraya,1)
               THISFORM.list1.REMOVEITEM(1)
            ENDFOR
            THISFORM._arraylib1.insaitem(@arrayb,stringval,thisval-1)
            THISFORM._arraylib1.delaitem(@arraya,thisval)
            FOR i=1 TO ALEN(arraya,1)
               THISFORM.list1.ADDITEM(arraya[i])
            NEXT
            THISFORM.list2.NUMBEROFELEMENTS=ALEN(arrayb,1)
            THISFORM.REFRESH
         ENDPROC

         PROCEDURE list2.CLICK
            LOCAL thisval
            thisval=THISFORM.list2.VALUE
            FOR i=1 TO ALEN(arrayb,1)
               THISFORM.list2.REMOVEITEM(1)
            ENDFOR
            stringval=arrayb(thisval)
            THISFORM._arraylib1.insaitem(@arraya,stringval)
            THISFORM._arraylib1.delaitem(@arrayb,thisval)
            FOR i=1 TO ALEN(arrayb,1)
               THISFORM.list2.ADDITEM(arrayb[i])
            NEXT
            THISFORM.list1.NUMBEROFELEMENTS=ALEN(arraya,1)
            THISFORM.REFRESH
         ENDPROC

         PROCEDURE command2.CLICK
            CLEAR EVENTS
         ENDPROC

      ENDDEFINE

In the Command window enter the following:
DO ARRAYLIB

Click Apple in the first list box and notice that Apple is inserted the first position of the second list box. Click Pear in the first list box and notice that Pear is inserted into the third position of the second list box.

This occurs because the numeric position of the array element from arraya passes to the _arraylib1.insaitem with the following syntax:
THISFORM._arraylib1.insaitem(@arrayb,stringval,thisval-1)
Consequently, the array element from arraya is inserted into arrayb at the same row it had in arraya.

Click Blueberry in the second list box noting that Blueberry is inserted at the bottom of the first list box.

This occurs because the numeric position of the array element from arrayb is not passing to the _arraylib1.insaitem method using the following syntax:
THISFORM._arraylib1.insaitem(@arraya,stringval)
Consequently, the array element from arrayb is inserted into the last row of arraya.

Additional query words: kbCodeSam kbVFp600 FxprgClassoop

Keywords : FxprgClassoop
Version : WINDOWS:6.0
Platform : WINDOWS
Issue type : kbhowto