Question

How can I add an arraylist attribute into a class using classic ASP?

My Example (Not working):

Class AA
    Public AA_id
    Dim data: set data = CreateObject("System.Collections.ArrayList")
End Class

Answer 1

You need to initialize class members inside a method – function, sub routine of the class constructor. Naturally, the best of these is inside the constructor.

Fully working code demonstrating how to use the .NET ArrayList as part of custom VBScript class:

<%
Class MyCustomClass
    Private internalArrayList

    Private Sub Class_Initialize()  
        Set internalArrayList = Server.CreateObject("System.Collections.ArrayList")
    End Sub  

    Private Sub Class_Terminate()  
        Set internalArrayList = Nothing
    End Sub  

    Public Sub AddItem(oItem)
        internalArrayList.Add(oItem)
    End Sub

    Public Function ToString()
        Dim data, x
        data = "List contains " & internalArrayList.Count & " item"
        If internalArrayList.Count<>1 Then data = data & "s"
        For x=0 To internalArrayList.Count-1
            data = data & "<br />"
            If IsObject(internalArrayList(x)) Then
                data = data & "complex object of type " & TypeName(internalArrayList(x))
            ElseIf IsArray(internalArrayList(x)) Then
                data = data & "array with " & (UBound(internalArrayList(x)) + 1) & " items"
            Else  
                data = data & internalArrayList(x)
            End If
        Next
        ToString = data
    End Function
End Class
%>

Usage sample, including adding a complex object:

Class Foo
    Public Dummy
End Class

Dim myInstance, myFoo
Set myInstance = New MyCustomClass
myInstance.AddItem("hello")
myInstance.AddItem("world")
myInstance.AddItem(Array(1, 2, 3))

Set myFoo = New Foo
myFoo.Dummy = "just checking"
myInstance.AddItem(myFoo)

Response.Write(myInstance.ToString())