From: Isaac Sanders <isaacbfsanders@...>
Date: 2011-11-21T05:41:28+09:00
Subject: Re: Principle of Best Principles

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If you are interested Ruby Design Patterns and Idioms, check out Russ
Olsen's books Design Patterns in Ruby and Eloquent Ruby. They really helped
to take my skills to the next level.

On Sun, Nov 20, 2011 at 2:42 PM, Intransition <transfire@gmail.com> wrote:

> I seem to run into a couple of design issue a lot and I never know what is
> really proper. On one hand I often hear that I should limit coupling and
> stick to single responsibility, but when I do I often find it difficult to
> get the information to part of the program when it is needed. For example,
>
>   class Singer
>     def initialize(name)
>       @name = name
>     end
>     attr :name
>   end
>
> Then should Song be:
>
>   class Song
>     def new(singer)
>       @singer = singer
>     end
>   end
>
> or
>
>   class Song
>     def new(singer_name)
>       @singer_name = singer_name
>     end
>   end
>
> The later has less coupling, so according to principles I should use it.
> But if I later discover something in Song needs to know more about the
> singer, I'm in a bad way. e.g.
>
>   class Song
>     ...
>     def play
>       puts "Belting it out by #{@singer.name}, winner of
> #{@singer.grammy_count} grammies!"
>     end
>   end
>
> I'd be in a fix if I had used the later Song class instead of the former.
> But then I suspect someone would remind me of SRP, single responsibility
> principle, and suggest instead:
>
>   class SongPlayer
>     def initialize(singer, song)
>       @singer, @song = singer, song
>     end
>     def play
>       puts "Belting it out by #{@singer.name}, winner of
> #{@singer.grammy_count} grammies!"
>     end
>   end
>
> And yea, I guess that makes sense, since another singer might do a cover
> of some one else's song, right? But then, would it really be the exact same
> song? In most of my cases it's never the same "song" so I never have that
> kind of scenario. So is the SRP worth the extra classes it brings to the
> code then?
>
> I sometimes think many OOP principles, SOLID or otherwise, arose out
> limitations of Java, and don't apply so well to Ruby.
>
>


-- 
Sincerely,

Isaac Sanders
Section C-4B Vice Chief, Order of the Arrow
Vice Chief of Administration, Tecumseh #65
Eagle Scout

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