OO conventions

[Daniel Nogradi]

> > So after all, what is a 'factory' or 'factory function'?
>
> A brief explanation in Python terms is at
> http://www.aleax.it/ep03_pydp.pdf -- "pages" (slides) 37-44 (the rest of
> the presentation is about an even more fundamental design pattern,
> "template method").  A far more extensive essay can be found, for
> example, at
> http://gsraj.tripod.com/design/creational/factory/factory.html -- it
> names the pattern "factory method", not "factory function" ("method" is
> probably a more widespread name for it) and presents examples in Java
> and Corba IDL.
>
> Anyway, trying to summarize:
>
> - "what": any function or method or other callable whose task it
> is to build and return new objects can be called "a factory";
>
> - sometimes a factory may get away with returning an existing
> object for recycling "as if" it was a new one, saving some
> resources, and this is one advantage;
>
> - a factory may choose what exact type of object to build and return
> based on arguments or other circumstances, and this is a second
> advantage.
>
> "Program to an interface, not to an implementation" -- the key
> underlying principle ot the gang of 4's "Design Patterns" book.
>
> If you build an object of a specific given type ("new Foo" in Java
> or C++), you're hardwiring the choice of implementation (the
> exact concrete type); delegating the building to a method or
> function frees your application from such hardwiring and lets
> it be concentrated (if needed at all) in one spot (the factory).
> [[With the "registry" pattern you may even be able to remove
> any hardwiring, but that's a pretty advanced and subtle idea]].
>
>
> Alex

Thank you very much, this helped a lot. Just one side note, the url
http://www.aleax.it/ep03_pydp.pdf should be
http://www.aleax.it/Python/ep03_pydp.pdf, I found your document there.
Thanks again.