From: Josh Cheek <josh.cheek@...>
Date: 2010-06-20T01:30:17+09:00
Subject: Re: General Ruby OOP question

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On Sat, Jun 19, 2010 at 8:56 AM, Paul A. <cyril.staff@gmail.com> wrote:

> Hello,
>
> I have a general question about OOP with Ruby.  If I have 2 class: Home
> and Person for instance, such as:
>
> >> class Home
> >>   def initialize
> >>     @person1 = Person.new
> >>     @person2 = Person.new
> >>     # ...
> >>   end
> >>
> >>   def open_a_window; end
> >>   # ...
> >> end
>
> >> class Person
> >>   def play_wii_game; end
> >> end
>
> Then, a home instance can include a lot of people. And that's cool.  And
> a home instance can apply action on a person using a method just like:
> @person2.play_wii_game
>
> But if a person want to open a window in its home?  Here, with a such
> design it's impossible, isn't it.
>
> So to allow this kind of action, I think we need to pass as parameter
> self inside Home initialization process, becoming:
>
> >> class Home
> >>   def initialize
> >>     @person1 = Person.new(self)
> >>     @person2 = Person.new(self)
> >>     # ...
> >>   end
> >>
> >>   def open_a_window; end
> >>   # ...
> >> end
>
> >> class Person
> >>   def initialize(home)
> >>     @home = home
> >>   end
> >>
> >>   def open_a_window
> >>     @home.open_a_window
> >>   end
> >>
> >>   def play_wii_game; end
> >> end
>
> Now, a instantiated person can do it using open_a_window proxy method.
> And any other proxifyable home's methods.
>
> But is it ethics? I mean, is that lawful under the principles of
> object-oriented programming. Maybe this is so much power, to pass self
> inside person instance inside its home... 'cause it's almost as if there
> was no class, no partitioning.
>
> What do you think about this?
> Thanks for any considerations.
> --
> Posted via http://www.ruby-forum.com/.
>
>
Plus, you get a nice little benefit in that the Person#open_a_window method
can contain the conditionals for dealing with the edge case of when there is
no home.

class Person
  def open_a_window
    @home.open_a_window if @home
  end
  def has_home?
    !!@home
  end
end

Then later you can say things like
person.open_a_window if person.hot?

rather than having to cart the exception logic all over your implementaion
person.open_a_window if person.hot? && person.has_home?

Though, I suppose, it is a rather limited model in that your person may be
at work, or at a friend's home.

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