From: "Vinícius Baggio Fuentes" <vinibaggio@...>
Date: 2010-05-06T22:43:20+09:00
Subject: Re: Class variable "scope"

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Great, much better, thanks for the reply, Rick!

On Thu, May 6, 2010 at 10:34 AM, Rick DeNatale <rick.denatale@gmail.com>wro=
te:

> 2010/5/6 Vin=EDcius Baggio Fuentes <vinibaggio@gmail.com>:
> > Hi all,
> >
> > I've been writing a library for me to play with metaprogramming as an
> > exercise, but then I got stuck
> > on a non-metaprogramming issue:
> >
> > ## a.rb
> > class A
> >  def self.add_something(*sth)
> >    @@my_things ||=3D []
> >    @@my_things << sth
> >  end
> >
> >  def self.my_things
> >    @@my_things
> >  end
> > end
> >
> > ## b.rb
> > require 'a'
> >
> > class B < A
> >  add_something :bag, :boots
> > end
> > require 'a'
> >
> > ## c.rb
> > class C < A
> >  add_something :sword, :shield
> > end
> >
> > The result, when requiring both c and b into an irb shell is, as
> expected:
> >
> > ruby-1.8.7-p249 > C.my_things
> >  =3D> [[:bag, :boots], [:sword, :shield]]
> > ruby-1.8.7-p249 > B.my_things
> >  =3D> [[:bag, :boots], [:sword, :shield]]
> >
> > I did achieve the following:
> >
> > C.my_things
> > [[:sword, :shield]]
> > B.my_things
> > [[:bag, :boots]]
> >
> > by moving my_things method into each child class and using the method o=
n
> the
> > add_something method, but there must be a better way. How one could
> improve
> > this?
>
> Use a class instance variable rather than a class variable.
>
> Also I suspect you really want to get [:sword, :shield] rather than
> [[:sword, :shield]]
>
> class A
>  def self.add_something(*sth)
>   @my_things ||=3D []
>    @my_things.concat sth
>  end
>
>  def self.my_things
>   @my_things
>  end
> end
>
>
> class B < A
>  add_something :bag, :boots
> end
>
> class C < A
>  add_something :sword, :shield
> end
>
> B.my_things # =3D> [:bag, :boots]
> C.my_things # =3D> [:sword, :shield]
>
> If you really want to get a array of arrays rather than a single level
> array, just change the .concat back to <<
>
>
> HTH
> --
> Rick DeNatale
>
> Blog: http://talklikeaduck.denhaven2.com/
> Github: http://github.com/rubyredrick
> Twitter: @RickDeNatale
> WWR: http://www.workingwithrails.com/person/9021-rick-denatale
> LinkedIn: http://www.linkedin.com/in/rickdenatale
>
>

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