October 9, 2005
Aspect Oriented Programming (AOP)
From the article:
What Is an Aspect?
When thinking of an object and its relationship to other objects we often think in terms of inheritance. We define some abstract class; let us use a Dog class as an example. As we identify similar classes but with unique behaviors of their own, we often use inheritance to extend the functionality. For instance, if we identified a Poodle we could say a Poodle Is A Dog, so Poodle inherits Dog. So far so good, but what happens when we define another unique behavior later on that we label as an Obedient Dog? Surely not all Dogs are obedient, so the Dog class cannot contain the obedience behavior. Furthermore, if we were to create an Obedient Dog class that inherited from Dog, then where would a Poodle fit in that hierarchy? A Poodle is A Dog, but a Poodle may or may not be obedient; does Poodle, then, inherit from Dog, or does Poodle inherit from Obedient Dog? Instead, we can look at obedience as an aspect that we apply to any type of Dog that is obedient, as opposed to inappropriately forcing that behavior in the Dog hierarchy.