"Chinook" wrote: > I understand what you are saying. The point I'm messing up my head with > though, is when the entity (tree node in my case or variable record content > deconstructing in the aspect example I noted) is not an instance of a class > already - it is obtained from an external source and only decipherable by its > content. > > In practical terms that leaves me with some decision sequence regardless and > I was wondering (from what Chris Smith said) how that might be done in OOP. > The whole problem may be that I'm reading too much into what Chris said :~) > I will dig back through the Tutor archives as you suggested.
What you are looking for is what is called the 'factory method pattern' (http://en.wikipedia.org/wiki/Factory_method_pattern) and it's one of the cases where OOP doesn't eliminate the if/elif/elif (or switch in C++/Java). That's ok though because, as you noticed, at some point you have to take a decision. What's important is the "once and only once" principle, that is all the decision logic is encapsulated in a single method (or in python in a single function) instead of being replicated every time you want to use an existing Node. Regards, George -- http://mail.python.org/mailman/listinfo/python-list
