Rails - Jan 2007 - Aliasing Active Record Attributes (also delegation issues)

This whole situation is a mess, but I''ll see if I can explain it well.

I have two models, User and Company.  I''d like user to be able to get
company.name.  I''m aware of the problems with using @user.company.name,
because of company is nil, then name throws an error.

So originally, I wrote this method instead

class User
  def company_name
    company ? company.name : nil
  end
end

This works, however, rather than use that, I would like to use delegation.
The problem I ran into with that,
however, is that user also has a name.  So I can''t simply write

class User
  delegate :name, :to => :company
end

because that will overwrite name.  It would be nice if there was a delegate
:company_name, :as => :name, :to => :company, but as far as I know this
doesn''t exist.  So... I thought I would use "delegate
:company_name: to =>
:company", and alias :company_name to :name within company, like so:

class Company
  alias :company_name :name
end

however, that will not work with Active Record models, because name is not
defined until the class is instantiated.  I could just write a wrapper
method, aka def class_name; name; end; but that adds an extra method call
that I''d rather not have.  So finally, I came up with this solution:

class Company
  def company_name
    name
    self.class.class_eval do
      alias_method :company_name, :name
    end
    name
  end
end


This works, because the first time company_name is called, it calls name to
instantiate it (needed the first call for some reason), then it opens the
class and aliases company_name to name.  Lastly, it returns name, so that it
works as intended on the first call as well.
This code does work, I have tested it, but it seems like an awful lot of
work for what seems like a simple concept.  Maybe I''m just making
things too
complicated, and should have simply used my company_name method within User,
I don''t know.

If anyone can suggest a better way to solve this problem, it would be much
appreciated.

Thanks,
Tyler Prete

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I''m not entirely sure, but i think @object.content.name only trows an
error if @object.content is nil AND you''re in development mode (whiny
nils is enabled). Not sure though.

On Jan 20, 9:05 pm, "Tyler Prete"
<psyo...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> This whole situation is a mess, but I''ll see if I can explain it
well.
>
> I have two models, User and Company.  I''d like user to be able to
get
> company.name.  I''m aware of the problems with using
@user.company.name,
> because of company is nil, then name throws an error.
>
> So originally, I wrote this method instead
>
> class User
>   def company_name
>     company ? company.name : nil
>   end
> end
>
> This works, however, rather than use that, I would like to use delegation.
> The problem I ran into with that,
> however, is that user also has a name.  So I can''t simply write
>
> class User
>   delegate :name, :to => :company
> end
>
> because that will overwrite name.  It would be nice if there was a delegate
> :company_name, :as => :name, :to => :company, but as far as I know
this
> doesn''t exist.  So... I thought I would use "delegate
:company_name: to =>
> :company", and alias :company_name to :name within company, like so:
>
> class Company
>   alias :company_name :name
> end
>
> however, that will not work with Active Record models, because name is not
> defined until the class is instantiated.  I could just write a wrapper
> method, aka def class_name; name; end; but that adds an extra method call
> that I''d rather not have.  So finally, I came up with this
solution:
>
> class Company
>   def company_name
>     name
>     self.class.class_eval do
>       alias_method :company_name, :name
>     end
>     name
>   end
> end
>
> This works, because the first time company_name is called, it calls name to
> instantiate it (needed the first call for some reason), then it opens the
> class and aliases company_name to name.  Lastly, it returns name, so that
it
> works as intended on the first call as well.
> This code does work, I have tested it, but it seems like an awful lot of
> work for what seems like a simple concept.  Maybe I''m just making
things too
> complicated, and should have simply used my company_name method within
User,
> I don''t know.
>
> If anyone can suggest a better way to solve this problem, it would be much
> appreciated.
> 
> Thanks,
> Tyler Prete

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On 1/20/07, Tyler Prete <psyonic-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> class Company
>   alias :company_name :name
> end
class Company
  alias_attribute :company_name, :name
end

-- 
Chris Wanstrath
http://errtheblog.com

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Chris,

Thanks!  Much much better.  I had the feeling that there had to be a better
way, and there it is.

--Tyler

P.S.  I really like your blog.  Lots of good information on there.

On 1/21/07, Chris Wanstrath <chris-G5sj8e7vJc8@public.gmane.org>
wrote:
>
>
> On 1/20/07, Tyler Prete
<psyonic-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > class Company
> >   alias :company_name :name
> > end
>
> class Company
>   alias_attribute :company_name, :name
> end
>
> --
> Chris Wanstrath
> http://errtheblog.com
>
> >
>
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