2018年12月02日

The Class of Collection in VB 6.

VB.NET offer many data structure like ArrayList, Queue, Stack, HashTable,

Collection etc., to hand the data, while VB 6.0 only support the Collection

object. In this article you will learn how to use Collection to implement something similar to Stack class in VB_NET.

Once you have created a collection object, you can do any one of the following:

(1)Add an element to the Collection uses the Add method.

(2)Remove an element that uses the Remove method

(3)Find out how many elements the Collection contains with the Count Property

(4)Return a specific element from the collection with the Item Property

(5) Use For Each … Next statement to show the element of a Collection

(6) Use Set Obj=Nothing to clear the items of a Collection

The Add method syntax are like:

object.Add(Item, [Key],[Before].[ After])

For example, to add a student order object to a collection using the student's ID property as its key, you can make the following call.

Dim StudentColl as new Collection

StudentColl.Add(“C.H Day”,”id_0”)

(a)Exmple of Add method of Collection

      If you want to order an array of number, you can use the powerful Add method of Collection., the following snippet codes are the implement to reorder and remove duplicate of an array.

Sub Order_Duplictae(iType As Integer, ListIn As ListBox)

Dim IntegerColl As New Collection

Set IntegerColl = Nothing 'Initialize

IntegerColl.Add (-9999)

IntegerColl.Add (99999)

Dim iTestA As Integer, iTestB As Integer

  Dim i As Integer, j As Integer

   For i = 0 To UBound(ArrayI)

     For j = 1 To IntegerColl.count - 1

           If iType = 0 Then 'Order

                If ArrayI(i) >= Val(IntegerColl.Item(j)) And ArrayI(i) <= Val(IntegerColl.Item(j + 1)) Then                    IntegerColl.Add ArrayI(i), , , j 'Add item after j                    GoTo 100

                 End If

           Else     'Remove duplicate

               If ArrayI(i) > Val(IntegerColl.Item(j)) And ArrayI(i) < Val(IntegerColl.Item(j + 1)) Then                    IntegerColl.Add ArrayI(i), , , j 'Add item after j                    GoTo 100

                 End If

           End If

   Next j

100:

   Next i

   'Remove the 1st item & Lastest item

   IntegerColl.Remove (1)

   IntegerColl.Remove (IntegerColl.count)

    'show member of the collection

    For i = 1 To IntegerColl.count

    ListIn.AddItem "Count= " & i & " ; " & IntegerColl.Item(i)

    Next i

 End Sub

(b)Implement of stack with Collection object

  VB 6 does not support the Stack object, but you can implement the stack method using Collection object.

Here we use Collection to Implement the Push() and Pop() of Stack()

 '! Push data into a collection(把資料放入堆疊中)

  Private Sub Push(value As Integer)

    'integer value

    If (Current > nTOP) Then '! over the capacity of a collection( 超過容量)

      Form3.Picture1.Print "Stack full."

      Exit Sub 'Return

    End If

    Current = Current + 1

    CollectMove.Add value ‘using Add method

    'Picture1.Print "Push " & value & " in"

  End Sub

  '! Pop data from a collection(從堆疊中取出資料)

  Private Function Pop(value As Integer) As Integer

    'integer value

    If (Current <= 0) Then '! nothing more to take off(已經沒有東西可以拿了)

      Pop = 1

      Exit Function 'Return

    End If

    value = CollectMove.Item(CollectMove.Count)

     CollectMove.Remove CollectMove.Count

     Current = Current - 1

    Pop = 0

  End Function

Figure 1 and figure 2 are the result of the program of one player Knight Chess In VB 6.0, in this program, I use Collection object to implement the stack method.

Figure 1

Figure 2

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