From: Rick DeNatale <rick.denatale@...>
Date: 2007-04-10T03:24:40+09:00
Subject: Re: method defined in module doesn't have access to Constant in class it is imported into

On 4/9/07, Mike Sandler <mike.sandler@gmail.com> wrote:
> Does anyone know why a method defined in a module that is then included in a
> class does not have
> access to the constants of that class?  Doesn't including the module make
> all its methods into instance methods
> of the class?  Shouldn't get_foo and class_get_foo in the following example
> work the same?
>
> module ModFoo
>   def get_foo
>      FOO
>   end
> end
>
> class Foo
>   FOO = 'this is foo'
>   include ModFoo
>
>   def class_get_foo
>      FOO
>   end
> end
>
>
> f = Foo.new
> f.get_foo
>
> >> f.get_foo
> NameError: uninitialized constant ModFoo::FOO
>         from (irb):3:in `get_foo'
>         from (irb):11
>         from :0
>
> f.class_get_foo
> => "this is foo"
>

Because Mod::FOO, and Foo::FOO are two different constants in two
different namespaces.

Included methods aren't source macros, they get compiled in the
context of the module that contains them, so when ModuleFoo#getFoo was
compiled, FOO got bound to ModuleFoo::FOO, hence the error.

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/