How To Use the _arraylib Class from _utility Class Library

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: 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: The code sample below illustrates use of the _arraylib class.

1. 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

2. In the Command window enter the following:

   DO ARRAYLIB

3. 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.
4. 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.