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This chapter is from the book

Adding and Overriding Methods

So far, I've created Beta, a subclass of Alpha, but that is all. Except for the type, there's really no difference between them. If you wanted to, you could add new methods to Beta that would be available only to Beta and not Alpha. This is easy enough to do—just add methods to Beta as you would to any class or module.

A more interesting thing you may consider doing is overriding an existing method.

Again, there is a shade of resemblance between object-oriented inheritance and human inheritance. Once in a while (as children are wont to do), the child decides to do something that the parent already does, but in a different way. For example, my father and I both go to church, but he goes to a Baptist church and I go to a Catholic one. In object-oriented circles, this is called overriding.

The way to override one of Alpha's methods in Beta is to implement a method with the exact (and I mean exact) signature as a method that is found in Alpha. Because Alpha implements only one method, getName() (well, two if you count the Constructor, which can also be overridden), we'll override getName() in Beta.

Function getName() as String
  Return "Beta says: " + me.Name
End Function

Now let's see how this works in practice.

Dim a as Alpha
Dim b as Beta
Dim s,t as String
a = New Alpha("Golly!")
b = New Beta("Golly!")
s = a.getName() // s = "Golly!"
t = b.getName() // b = "Beta says: Golly!"
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