Re: Question
Re: Question
- Subject: Re: Question
- From: Greg Titus <email@hidden>
- Date: Sun, 2 Dec 2001 20:58:09 -0800
On Sunday, December 2, 2001, at 06:43 PM, Eduardo I. Jiminez wrote:
Hi. I am not exactly an expert in Cocoa, but I am not a beginner.
Now, I'm trying to develop a very complex application. This application
has a very complex design in terms of classes and relationships (about
150+ classes). Now, my basic problem is the following: this design has
many classes with multiple inheritance. I've tried to think of ways of
dealing with the problem, but I have not found an elegant solution. My
last resort is developing the "model" part of my application in C++,
which offers the features I need to implement this, and then using
those C++ classes from the "Controller" in my Cocoa application. Could
someone brief me in the complexities of doing this?. What kinds of
problems can I run into.
Also, does anyone have an useful resource available about how to model
multiple inheritance in non-multiple inheritance capable languages? I
know there are many papers available, but some digested online resource
(or advice) would be helpful.
You are asking the wrong question, I think - at least, it's the wrong
question if you want a good answer. The way you are asking it you are
almost guaranteed to get an unsatisfactory answer and to come away with
the opinion that Objective-C and Java lacking multiple inheritance is a
_bad_ thing. :-)
You don't really want to model multiple inheritance, per se, you want to
model some specific kinds of relationships between your classes and you
are used to using multiple inheritance in C++ to do so.
There are several different reasons why people generally end up using
multiple inheritance in C++, and in the case of Cocoa they might map
most suitably to one or more of: protocols, categories, composite
objects, forwarding, et cetera. It really depends on the reason why you
were doing it in the first place. It's very likely that there will be
several different approaches for different parts of your object model
that are the best fit instead of a single "do multiple inheritance this
way".
I could go into a lot of detail about the different kinds... (One quick
example: one use of MI in C++ is a base class with all virtual members
and then many other classes inheriting from that class as a way to deal
with many different types of otherwise unrelated objects that all
implement the same set of methods. In Java you'd use an interface
instead. In Objective-C you'd use either a formal or informal protocol -
and which was best would depend on other things. That's the very easiest
example because it's an area where I can point to a specific language
feature which is a much better fit for the design pattern than MI.) But
we'd quickly get bogged down in all the different ways to do things
described in very general and nearly useless terms, and I'd still
probably miss some of the patterns that end up being in your design.
If you are willing to go into some more detail about what your class
design is trying to accomplish we (I) could probably be more helpful.
--Greg
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| | >Question (From: "Eduardo I. Jiménez" <email@hidden>) |