Is there a better way to call each derived object's method for a base class?

Question

I have a base class where I derive several classes. I have another class that uses all those derived classes in a different way. However, I want to call the Update() method (inherited from the base class) on each derived class. Is there an easy way to do this, or do I have to do something like:

dim a As Derived1
a.Update

dim b As Derived2
b.Update

etc...

Answer 1

I think the best way to do this is to keep the derived objects in a list of some kind, and then iterate over them to call Update.

In pseudo-code:

foreach BaseClass item in {a, b, ...}:
    item.Update

Answer 2

You can do that through polymorphism with a function call that's passed the base class (pseudo-code):

Dim Dev1 as Derived1 '// This is derived from the class BaseClass
Dim Dev2 as Derived2 '// This is derived from the class BaseClass

CallUpdate(Dev1)
CallUpdate(Dev2)

Function CallUpdate(BaseClass bc)
    bc.Update()
End Function