From: Juston Davies <justondavies@...>
Date: 2009-07-22T07:02:37+09:00
Subject: Re: define_method in inheritance

Awesome, thats what I wanted to hear. Thanks for the help!

On Jul 21, 3:20 pm, "David A. Black" <dbl...@rubypal.com> wrote:
> Hi --
>
>
>
> On Wed, 22 Jul 2009, Juston Davies wrote:
> > I had a quick question about something I had read in a book "The Ruby
> > Way." The author talks about different ways to dynamically define
> > methods during runtime using something similar to the snippet below.
>
> >  def define_method (name, &array)
> >    self.class.send(:define_method, name,&array)
> >  end
>
> > This opens up the scope of a given class so any other class could add
> > methods on the fly. My question is that if I were to insert this code
> > into a parent and then invoke it on a child would the new method be
> > defined within the scope of the child or the parent? I'm concerned
> > that this might result in adding methods into all the children rather
> > than just the desired one. Let me know what you think. Thanks in
> > advance!
>
> It will define the method in self.class, which will be the class of
> whatever object you call it on. The new method will also be available
> to instances of subclasses of that class.
>
> class A
>    def define_method(name, &block)
>      self.class.send(:define_method, name, &block)
>    end
> end
>
> class B < A
> end
>
> class C < B
> end
>
> b = B.new
> b.define_method(:x) { puts "In x!" }
>
> b.x       # In x!
>
> c = C.new
> c.x       # In x!
>
> a = A.new
> a.x       # Unknown method x
>
> David
>
> --
> David A. Black / Ruby Power and Light, LLC
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