From: Erik Veenstra <erikveen@...>
Date: 2006-07-23T01:01:41+09:00
Subject: *_eval

Can somebody explain me, in detail, the differences between
aModule.instance_eval, aModule.module_eval and
aModule.class_eval?

I'm especially interested in the differences in context.

There must be a difference. If I replace aModule.module_eval
with aModule.instance_eval in one spcific situation, the
results differ, although self.inspect returns the same value...

Thanks.

gegroet,
Erik V. - http://www.erikveen.dds.nl/

----------------------------------------------------------------

 class Object
   def metaclass
     class << self
       self
     end
   end
 end

 class Foo
   block =
   lambda do
     p [self, object_id]
   end

   2.times do
     instance_eval(&block)
     module_eval(&block)
     class_eval(&block)

     metaclass.instance_eval(&block)
     metaclass.module_eval(&block)
     metaclass.class_eval(&block)
   end
 end

----------------------------------------------------------------

 [Foo, -605291388]
 [Foo, -605291388]
 [Foo, -605291388]
 [#<Class:Foo> , -605291428]
 [#<Class:Foo> , -605291428]
 [#<Class:Foo> , -605291428]
 [Foo, -605291388]
 [Foo, -605291388]
 [Foo, -605291388]
 [#<Class:Foo> , -605291428]
 [#<Class:Foo> , -605291428]
 [#<Class:Foo> , -605291428]

----------------------------------------------------------------