Testing a Variable for Instantiation [vb.net]

[NeuralJack]

Sometimes when I define a variable holding a class I dont want to instantiate it until later.. possibly in another function even. This means for safety I'd like to be able to test that it's been instantiated before I acutally use it, to avoid errors. So how can I test for instantiation of a class I made?

 

Dim Bob as MyClass  'Not instantiated

'So i want something like ..
If Bob <> Nothing Then
'Continue..
End if

'But i'm pretty sure that <> Nothing doesnt work on classes

[MrPaul]

Is and IsNot

 

You can compare references in VB.Net using Is and IsNot:

 

If (bob Is Nothing) Then
   'Not instantiated
End If

If (bob IsNot Nothing) Then
   'Instantiated
End If

If (bob Is bill) Then
   'bob and bill reference the same object
End If

'etc

 

Good luck :cool:

[NeuralJack]

Thanks Mr. Paul! you rock.

[Nerseus]

If you didn't already know, what you're doing is generally called "lazy loading" or similar. The idea is only instantiate the object when it's needed. Thought I'd throw out that term in case you found it useful in google searches.

 

-ner