From: Robert Klemme <bob.news@...>
Date: 2004-08-15T00:01:11+09:00
Subject: Re: Opinion on ClassInherit Include


"T. Onoma" <transami@runbox.com> schrieb im Newsbeitrag
news:200408141028.42017.transami@runbox.com...
> On Saturday 14 August 2004 10:06 am, Robert Klemme wrote:
> > You didn't say so in your original post.  And as far as I can see you
have
> > two modules in your example, too.  As you obviously noticed, you need to
> > identify those parts that should go into instances and those for the
class
> > *somehow*.  So having two separate modules is really the simplest way.
>
> Okay, more detail then.
>
> Currently I have a class that can be subclassed to inherit behavior, but I
> want to turn that into a mixin module instead. Problem is that the class
has
> class methods that need to be inherited too. Can't do that with a module,
so
> I had to figure out a way. Of course I could use two *seperate* modules,
as
> you say, but then the lib user would have to add two lines of code (an
> include and an extend) to get functionality that really belongs together.
>
> So let me ask it this way: I have class behavior and instance behavior
that
> needs to encapsulated into a single mixin unit. How to do it?

You probably want this which works with a single (!) module.  Ha!

module Foo
  class <<self
    attr_accessor :foo
  end

  attr_accessor :bar

  def self.append_features(cl)
    # need a copy of me to avoid state interference
    copy = dup
    cls = class<<cl;self;end

    copy.singleton_methods.each do |m|
      cls.send(:define_method, m, copy.method(m).to_proc)
    end

    super
  end
end
Foo.foo = "Foo.foo"
p Foo.foo

class Bar
  include Foo
end

bar = Bar.new
bar.bar = "bar.bar"
p bar.bar

Bar.foo = "Bar.foo"
p Bar.foo
# ensure Foo.foo is unchanged
p Foo.foo


Regards

    robert