Michael Langford wrote: > Inheritance: Syntactic sugar that's not really needed to make a well > organized system. Often overused, especially by programmers in big > companies, beginning students of programmers, green engineers, and > professors. In practice hides a lot of data, often making behavior > surprising, therefore harder to maintain. Can be used in limited situations > to great advantage, but like cologne on car salesmen, is used in greater > amounts than it should be. One should always ask, can I make a simpler > system with composition.
Pretty much exactly what my colleague said. Having thought about it I understand this. > Polymorphism: The process of creating many classes which a single interface > which are then all used by an object that doesn't know or need to know the > type. Many people think you only get this by using inheritance and therefore > use inheritance many places a simpler, less opaque, more lightweight > solution will work. Most dynamically typed languages (most notably, python, > ruby and smalltalk) don't even require you specify the interface explicitly > to get polymorphic behavior. C++ templates can do non-explicit interface > polymorphism, however in a more complicated, blindingly fast to run, > blindingly slow to compile way. Also what my colleague said! This is the bit I had missed. Perhaps I need to rethink / reload my understanding of polymorphism. > Encapsulation: The process of taking what shouldn't matter to the external > world, and locking it behind an interface. This principle works best when > put into small, specialized libraries and designed for general use, as this > is the only encapsulated form that is shown to last over time. Supposedly > something OO based design allows, but in reality, the coupling among classes > varies in differing amounts. The module/public visibility of Java is a good > compromise with classes that hides some data but share some with certain > other classes. C++ has large issues for historical reasons on this front, as > the implementation section of a class is largely revealed through the class > definition. Interesting. And again revealing of a weakness in my understanding. I do think this is a good question for getting a sense of where a person's understanding is. I wonder how much this understanding is a pre-requistite for being a good developer... not too much I hope! > --Michael S. _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
