Do you find yourself writing the same methods over and over in different classes? Say your project needs both a “Dog” class and a “Cat” class — do you end up writing a “sleep” method for both? What if, in two months, the client needs you to add a “possum” to the system? Do you end up going in and retyping “sleep” instructions yet again? When you’re modeling a system with many similar parts, it takes way too much time and effort to keep duplicating code for each class. Imagine how hard it would be to maintain a large project with thousands of classes! Besides, it violates the DRY principle of good programming: Don’t Repeat Yourself! There must be a better way. Read the rest of this entry »