From: Carl Youngblood <youngblood.carl@...>
Date: 2008-02-05T23:23:19+09:00
Subject: Re: eval vs. class_eval

Day wrote:
> On Feb 4, 2008 4:16 PM, Thomas Wieczorek <wieczo.yo@googlemail.com> 
> wrote:
> 
>> eval and class_eval work on different scopes. eval works just in its
>> current scope(here your method), however class_eval works for the
>> whole class(your Fil)
> 
> 
> Are you saying there's some kind of weird scope shift up? If you run 
> version
> two (with eval) and create a child class and a grandchild class, it 
> looks
> like it creates the grandchild within Fil, not within Fil's child. The
> class_eval version creates it so that Fil's child is within Fil and 
> Fil's
> grandchild is within Fil's child. At least... that's what's baffling to 
> ME
> about this. Maybe Carl can provide an example.
> 
> If I'm guessing totally wrong, what's going on, exactly, with the scope
> here?
> 
> 
> Ben

Right.

The structure I observe with running the eval version is

class Fil
  class NewClass1
  end
  class NewClass2
  end
end

but running class_eval I observe

class Fil
  class NewClass1
    class NewClass2
    end
  end
end

I believe the second form should be the result for either eval or 
class_eval since they both default to a receiver of self, and when 
adding NewClass2 the receiver self should be Fil::NewClass1, not Fil.

I'm guessing either what I'm observing is wrong somehow or there is a 
special rule about eval and the context it evaluates in?

Carl
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