Question

Imagine I have a game with a base Entity class, with an init method that takes no arguments. Now I have a Wizard class, but I want to pass in 2 parameters, say speed and strength. In AS3 (and I believe Java and C#) I will not be allowed to do this – it is an “incompatible override” because the method signatures won’t match. Now I could just make an “initWizard” method instead, but then I have the problem of the init method of each class potentially having different names.

I need solutions that work in AS3, Java or C#.

Answer 1

Not sure I understood your question correctly. But the following compiles in Java:

public class A {
    public void init(int a) {}
}

public class B extends A {

    public void init( int a, int b )
    {
        super.init( a );
    }
}

Though I agree that B#init(int,int) is not an override of A#init(int), and B#init(int) can still be called. You can not really hide the existence of B#init(int), at best, you could override it in B and let it throw an exception if it is called.

Is it however so a big problem? The method signature capture only part of the contract of how a class must be used. If you want to shield your code a bit more, you could use a factory method to create instances of A or B and make init protected.

public class A {
    protected void init(int a) {}

    static public A create( int a)
    {
        A o = new A();
        o.init( a );
        return o;
    }
}

public class B extends A {

    protected void init( int a, int b )
    {
        super.init( a );
    }

    static public B create( int a, int b)
    {
        B o = new B();
        o.init( a, b );
        return o;
    }
}