"Greg Perry" <[EMAIL PROTECTED]> wrote > I am still in the process of learning OOP concepts and > reasons why classes should be used instead of > functions etc.
That's OK, many folks find the transition hard at first. It is a new way of looking at problems. > One thing that is not apparent to me is the best way > for classes to communicate with each other. Classes don't. Its *object* oriented programming and its objects which communicate. Objects pass messages between each other and the parameters are other objects. Classes are just the mechanisms for defining and creating objects. And thats a very important distinction. > For example, I have created an Args class that sets > a variety of internal variables (__filename, __outputdir etc) > by parsing the argv array from th command line. OK, What is the responsibility of an Args object? What kind of things would you do with/to an Args instance? You might want to get the vatrious values from it - treating it somewhat like a dictionary maybe? You might want to store it so the same set of args can be used over and over. What else do you want the args to do? Focus on the responsibility of the object as a whole. > What would be the preferred mechanism for returning > or passing along those variables to another class? You pass an instance of the args class as an object to another object via a message. > Maybe by a function method that returns all of those variables? You might have a method of the Args class that can get the values for a given instance but you wouldn't want to extract the values from the object and manage them elsewhere. That would be to defeat the point of the object, which is to encapsulate both the data and the operations on the data in one entity, the object, which can be passed around in its entirety. For example when you drive your car(an object) you don't dismantle it and then reassemble just the bits you need. Let's see its only me so only one seat and its a warm day so I don't need the heater... You just jump into the complete car and drive it. Same with your args class(*). You create an instance and use it whichever way you need. If somebody else needs your args to do something you give them the args (just like if somebody borrows your car you don't give them bits of it you lend them the whole car) (*)And same with the car, you don't lend someone the factory blueprint (the class) and tell them to build their own car, you lend them your specific instance of the car. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
