Returning Null or Nothing from VBScript function? - vbscript

Question

I'm trying to write the VBScript equivalent of a function similar to what's below:
object getObject(str)
{
if ( ... )
{
return object_goes_here;
}
return null;
}
My guess would be below, except that I'm not understanding the difference between Nothing and Null. As a caller, I'd rather test if the return value is set by using IsNull() versus X Is Nothing.
Function getObject(str)
If ... Then
Set getObject = object_goes_here
Exit Function
End If
Set getObject = Nothing // <-- or should this be Null?
End Function

Answer 1

The correct way to not return an object is to return Nothing and test for Is Nothing.
VB's Null is a special value of type Variant/Null. There are other special values, such as Variant/Empty or Variant/Error. They all have their use, but it's not the one.

Answer 2

Use the second Function skeleton. Avoid Null when dealing with objects, because of the Set Assignment abomination.
Dim oX : Set oX = getObject(...)
If oX Is Nothing Then
...
Else
nice object to work with here
End If
vs
Dim vX : vX = getObject(...) ' <-- no Set, no object
If IsNull(vX) Then
...
Else
no object to work with here
End If

Answer 3

In your sample code, the object gets always Nothing because that is the last action. This is how it should be:
Function getObject(str)
If ... Then
Set getObject = object_goes_here
Exit Function
End If
Set getObject = Nothing
End Function
or:
Function getObject(str)
Set getObject = Nothing
If ... Then
Set getObject = object_goes_here
End If
End Function
The answer of GSerg is correct: you should use Nothing. Additionally, to see if an object has a null reference, use:
If Not object Is Nothing Then
' do something
End If