From: Paul Lutus <nospam@...>
Date: 2006-10-27T06:10:11+09:00
Subject: Re: newbie q on class Foo::Bar

matt neuburg wrote:

> What's the point of a class-within-a-class? For example, I take it that
> I can say:
> 
> class Foo
>   class Bar
>     def whatever
>     ...
> 
> And then I can say
> 
> my_foo_bar = Foo::Bar.new
> 
> For example, isn't that what something like File::Stat is?
> 
> My question is, am I right about this, and if so, what's the point of
> doing so? I take it that Bar is not magically related to Foo - it can't
> see Foo's methods or anything like that, can it? So is this merely a way
> of using a class (Foo) as a namespace so that related classes (like Bar)
> are all in one place? Thx - m.

One reason is to create a class that is private. You may be aware that one
wants to separate results from implementation (separate the result from the
method used to produce the result), this can extend to classes that need to
exist, but don't need to be made available as part of the interface. That
way, the programmer can change the class without having to ask what
external effects this might have.

There are other reasons, this is just one.

-- 
Paul Lutus
http://www.arachnoid.com