From: "ara.t.howard" <ara.t.howard@...>
Date: 2008-11-10T06:32:28+09:00
Subject: Re: shared-0.4.2


On Nov 9, 2008, at 2:00 PM, Stefan Rusterholz wrote:

> Hi Ara
>
> Thanks a lot for sharing another of your fine libraries :)
> May I ask why I would introduce the dependency 'shared' instead of  
> using
> rubys native code sharing facility that is inheritance and (IMO more
> powerful) modules? Where do you see the striking advantages of shared?
>
> Regards
> Stefan


well, for starters it *is* based on modules ;-)  the striking  
advantage is, as a for instance, that you can do this in rails

in lib/shared.rb

shared :before_filters  do
   before_filter :foo
   before_filter :bar

   def foo() end
   def bar() end
end

in app/controllers/foo_controller.rb

class Foo < ApplicationController
   include shared(:before_filters)
end

in app/controllers/bar/controller.rb

class Bar < ApplicationController
   include shared(:before_filters)
end


this is absolutely not easily done with modules.  shared.rb has all  
the advantages of ruby module sharing *plus* the simplicity of  
completely POLS class level method sharing.

another example, which is not easily done using modules

in lib/shared.rb

shared :home_controller do
   before_filter :must_have_user

   def index
      render 'shared/home'
   end

protected
   def must_have_user() end
end

in app/controllers/teacher/home_controller.rb

class Teacher::HomeController < ApplicationController
   include shared(:home_controller)
end

in app/controllers/student/home_controller.rb

class Student::HomeController < ApplicationController
   include shared(:home_controller)
end



so, in that example, we can directly setup a public method (index  
action) and protected method, and call a class method.  try doing that  
with modules and you'll see that it's rather un-natural.  the call to  
before_filter, for instance, cannot simply be wrapped with the normal  
'ClassMethods' hack, but must actually be deferred because it only  
*exists* in the target classes - aka it doesn't exist in the mixin but  
only exists in the mixxee (controllers) making it a chicken-and-egg  
issue when code sharing is desired.

shared let's you factor out chunks of code *exactly* as you would have  
typed them before and then, later, to inject them into classes or  
module or objects *exactly as if you'd entered the code there*

make sense?

cheers.
a @ http://codeforpeople.com/
--
we can deny everything, except that we have the possibility of being  
better. simply reflect on that.
h.h. the 14th dalai lama