{Q} OOP Animal class.

[Will Ware]

johnvert at my-deja.com wrote:
> 1. I call the method reply()
> 2. The interperter sees reply() does not exist in class Hacker
> 3. It goes one class up the hierarchy to class Primate
> 4. reply() doesn't exist in class Primate
> 5. It goes one class up the hierarchy to class Mammal
> 6. reply() doesn't exist in class Mammal either
> 7. It goes one class up the hierarchy to class Animal

Good so far. As you suspected, this is where things start to
get a bit dicey. My understanding (which perhaps others will correct
if necessary) is that each method search is a separate thing, and in
each case we are prepared to climb the inheritance tree. So when
reply() calls speak(), we begin the whole search process anew, starting
at Hacker. Hacker doesn't have a speak() method, but Primate does,
and that's why we use Primate.speak().

> I really want to have a solid understanding
> of this because it's important to understand OOP.

OOP is primarily a flexible way to let you make say things like this:

	A Blarndoogle is an object with this set of behaviors.
	A Flugestroid is almost exactly like a Blarndoogle, except
	that it splointers the way a Zargrove does, and it has its
	own unique way of flithering, different from either a
	Blarndoogle or a Zargrove.

The idea would be that the behaviors for Blarndoogles and Zargroves
would probably already be thoroughly debugged when you were ready to
define a Flugestroid, so the only really new thing you need to do is
define how it flithers. That is, all your effort is focussed entirely
on what's new about this situation, not on re-implementing and
re-debugging existing behaviors. At least that's the theory.

Some languages (Python generally not among them) stress a "privacy"
aspect of objects, that there should be information available only to
the object and not to anybody else, and the object can therefore define
how others get to view or modify that information. Python mostly
doesn't worry about object privacy much; you can create private
attributes by starting attribute names with two underscores, but you
don't have the elaborate machinations of public/protected/private you
get with C++ and Java.
-- 
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Resistance is futile. Capacitance is efficacious.
Will Ware	email:    wware @ world.std.com