From: Mark Hubbart <discordantus@...>
Date: 2005-05-17T06:39:49+09:00
Subject: Re: Problems with the "outer scope" operator

On 5/16/05, Lothar Scholz <mailinglists@scriptolutions.com> wrote:
> Hello Martin,
> 
> MH> not sure if I entirely understand what you mean, but consider this:
> 
> MH> class Outer
> MH> end
> 
> MH> class Inner
> MH>   class Outer
> MH>   end
> 
> MH>   class Child1 < Outer
> MH>   end
> 
> MH>   class Child2 < ::Outer
> MH>   end
> MH> end
> 
> MH> Without the leading '::', Child2 would derive from Inner::Outer and not ::Outer.
> 
> Okay thats a good example that i understand.
> But why does somebody write
> 
> module SOAP
> module RPC
> class SOAPlet
> class RequestRouter < ::SOAP::RPC::Router
> end
> end
> end
> end
> 
> As soon as "::" is found inside the superclass doesn't this
> automatically mean we start the lookup inside the toplevel scope ?
> 
> Or would a "class RequestRouter < SOAP::RPC::Router" declaration really
> look for the following classes and and takes the first it finds in
> this order:
> 
> SAOP::RPC::SOAPlet::SOAP::RPC::Router
> SAOP::RPC::SOAP::RPC::Router
> SAOP::SOAP::RPC::Router
> SOAP::RPC::Router

Actually, it could easily fail if not for the leading ::

See here:

  module One; module Two; module Three; end end end
    ==>nil
  module One::Two::Three
    class One
    end
  end
    ==>nil
  module One::Two::Three
    class Uno < One::Two::Three::One
    end
  end
NameError: uninitialized constant One::Two::Three::One::Two
        from (irb):11


The subclasssing fails because it finds a constant named "One" in the
current scope, then fails to find "Two" as a subconstant. This results
in a NameError.

> And this raises one more question for me. Is there any differences in
> the lookup mechanism between nesting inside a module or a class ?
> 
> Sorry for the line noise, i posted this by accident to the core
> mailing list and not to the ruby-user list. And i hope someday we have a
> written (english !) formal language definition where i can find all
> the answers.
> 
> --
>  Best regards,                        emailto: scholz at scriptolutions dot com
>  Lothar Scholz                        http://www.ruby-ide.com
>  CTO Scriptolutions                   Ruby, PHP, Python IDE 's
> 
>