What is composition as it relates to object oriented design?

Question

I hear (and read on this site) a lot about \"favour composition over inheritance\".

But what is Compositon? I understand inheritance from the point of Person : Mamma

Answer 1

There are three ways to give behavior to a class. You can write that behavior into the class; you can inherit from a class that has the desired behavior; or you can incorporate a class with the desired behavior into your class as a field, or member variable. The last two represent forms of code reuse, and the final one - composition - is generally preferred. It doesn't actually give your class the desired behavior - you still need to call the method on the field - but it puts fewer constraints on your class design and results in easier to test and easier to debug code. Inheritance has its place, but composition should be preferred.