When would I use the delegation pattern instead of inheritence to extend a classs behavior?
Both delegation and inheritance are important concepts in object-oriented software design, but not everyone would label them as patterns. In particular, the seminal book on design patterns by the Gang of Four contains a discussion of inheritance and delegation, but the authors do not treat these topics as specific patterns. It is reasonable to think of them as design concepts which are more general than specific design patterns. Inheritance is a relationship between two classes where one class, called a subclass in this context, inherits the attributes and operations of another class, called its superclass. Inheritance can be a powerful design/reuse technique, especially when it is used in the context of the Liskov Substitution Principle. (The article by Robert Martin at http://www.objectmentor.com/publications/lsp.pdf provides an excellent explanation of the ideas behind Barbara Liskovs original paper on using inheritance correctly.) The primary advantages of inheritance are • it is d
