Overload constructors in VBScript

Question

I found a way to extend classes in VBScript, but are there any ways to pass in parameters or overload the constructor? I am currently using an Init function to initialize the p

Answer 1

You can work around it by having your Init function returning the object itself...

Class Test
  Private m_s
  Public Function Init(s)
    m_s = s
    Set Init = Me
  End Function
  Public Function Hello()
    Hello = m_s
  End Function
End Class

Dim o
Set o = (New Test).Init("hello world")
Echo o.Hello

Answer 2

Just to alter slightly on svinto's method...

Class Test
  Private m_s
  Public Default Function Init(s)
    m_s = s
    Set Init = Me
  End Function
  Public Function Hello()
    Hello = m_s
  End Function
End Class

Dim o : Set o = (New Test)("hello world")

Is how I do it. Sadly no overloading though.

[edit] Though if you really wanted to you could do something like this...

Class Test
    Private m_s
    Private m_i

    Public Default Function Init(parameters)
         Select Case UBound(parameters)
             Case 0
                Set Init = InitOneParam(parameters(0))
             Case 1
                Set Init = InitTwoParam(parameters(0), parameters(1))
             Else Case
                Set Init = Me
         End Select
    End Function

    Private Function InitOneParam(parameter1)
        If TypeName(parameter1) = "String" Then
            m_s = parameter1
        Else
            m_i = parameter1
        End If
        Set InitOneParam = Me
    End Function

    Private Function InitTwoParam(parameter1, parameter2)
        m_s = parameter1
        m_i = parameter2
        Set InitTwoParam = Me
    End Function
End Class

Which gives the constructors...

Test()
Test(string)
Test(integer)
Test(string, integer)

which you can call as:

Dim o : Set o = (New Test)(Array())
Dim o : Set o = (New Test)(Array("Hello World"))
Dim o : Set o = (New Test)(Array(1024))
Dim o : Set o = (New Test)(Array("Hello World", 1024))

Bit of a pain though.

Answer 3

A bit hackish, for sure, but when I need varargs in calls, one of my parameters I pass in as an array, i.e.

Rem printf done poorly
sub printf(fmt, args)
  dim fp, vap:
  dim outs:
  dim fini:
      fini = 0:
      vap = 0:
  while (not fini)
    fp = index(fmt,"%"):
    if (not(isNull(fp))) then
        ' do something with %f, %s
        select case(fp)
        case 'c':
          outs = outs & charparse(args(vap)):
        case 's':
          outs = outs & args(vap):
        ' and so on.  Quite incomplete but you get the idea.
        end select
        vap = vap + 1
    end if
  wend
end sub

printf("%s %d\n",array("Hello World", 42)):

Answer 4

You have to do it in two steps. VB Script doesn't support overloading so you can't modify the default constructor with new parameters. Same goes for Vb6