From: dblack@...
Date: 2006-10-02T04:37:36+09:00
Subject: Re: dynamic include

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Hi --

On Mon, 2 Oct 2006, David Vallner wrote:

> Florian A=DFmann wrote:
>> To be complete here if the Exception:
>>
>> NameError: undefined local variable or method `role' for
>> #<Class:#<Person:0x2869aa0>>
>>
>
> I smell a Ruby bug / gotcha.
>
> Apparently, in metaclass scope, the surrounding scope just isn't visible.

The class keyword always creates a new scope, whether you give it a
constant argument or a "<< obj"-style argument.

> Try a workaround:
>
> person.roles.each do |role|
>    if role.class.const_defined?('Functions')
>        class << person
> =09    self
>        end.class_eval do
>            include role.class.const_get('Functions')
>        end
>    end
> end unless person.nil?

You could also use extend, and avoid having to do the thing that won't
be easy until RCR 231 is accepted :-)

   person.roles.each do |role|
     if role.class.const_defined?('Functions')
       person.extend role.class.const_get('Functions')
     end
   end


David

--=20
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org
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