Overload constructors in VBScript - 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 properties, but would like to be able to do this when I create the object.
This is my sample class:
Class Test
Private strText
Public Property Get Text
Text = strText
End Property
Public Property Let Text(strIn)
strText = strIn
End Property
Private Sub Class_Initialize()
Init
End Sub
Private Sub Class_Terminate()
End Sub
Private Function Init
strText = "Start Text"
End Function
End Class
And I create it
Set objTest = New Test
But would like to do something like this
Set objTest = New Test(strInitText)
Is this possible, or does the object have to be created and initialized in two setps?

Answer 1

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 2

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 3

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

Answer 4

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)):