From: Robert Dober <robert.dober@...>
Date: 2010-04-13T02:41:12+09:00
Subject: Re: Nuances of alias_method

On Mon, Apr 12, 2010 at 7:08 PM, Richard Leber <rleber@mindspring.com> wrote:
> I am stumbling around some of the nuances of Ruby classes, especially in
> regard to alias_method. Specifically, can someone explain to me why this
> doesn't work:
>
>  class A
>    def A.foo
>      "Hello"
>    end
>  end
>
>  A.send(:alias_method, :bar, :foo) # => NameError: undefined method
> `foo' for class `A'
>
> But this does:
>
>  class A
>    def A.foo
>      "Hello"
>    end
>  end
>
>  class << A
>    alias_method :bar, :foo
>  end
>
>  A.foo # => Hello
>  A.bar # => Hello
> --
> Posted via http://www.ruby-forum.com/.
>
Well alias_method aliases instance methods, as foo is not an instance
method of class A it cannot be aliased there. But as foo is an
instance method of the singleton class of A (class << A) it can be
aliased there.
IOW
class A
  def foo; 42 end
end
now foo is an instance method of A and not of (class << A) and thus
your A.send...
would work, as would
A.module_eval do
  alias_

or
class A
  alias_...
end


HTH
Robert
>



-- 
Learning without thought is labor lost; thought without learning is perilous.”
--- Confucius