Using a class to extend a singleton?

ruby-talk
1

Given:

  class X
    def yo=x; @yo=x; end
  end

  class Y
    def yo!; puts @yo; end
  end

  x = X.new

Is there any way to extend x with Y's functionality (without going
back and changing the given code)? Eg.

>> x.yo="Hello World"
>> x.yo!
Hello World

T.

2

class << x; Y.instance_methods.each {|m| define_method m, Y.method(:m)}; end

kind of. brings in Object onwards, though, but that's easy to fix.

-ehird

···

On 01/03/2008, Trans <transfire@gmail.com> wrote:

Given:

  class X
    def yo=x; @yo=x; end
  end

  class Y
    def yo!; puts @yo; end
  end

  x = X.new

Is there any way to extend x with Y's functionality (without going
back and changing the given code)? Eg.

  >> x.yo="Hello World"
  >> x.yo!
  Hello World

T.

3

Almost but not quite. You'd have to use Y.instance_method(:m) instead,
but then you get an error anyway because Y is not a subclass of X or
something to that effect.

I don't think there is any reasonable way. It's too bad. After the
discussion on MP, I decided to take a second shot at better
encapsulation of Facets. One idea was to just have a special way to
load them --if I could do the above that would work. But no go there
and nfortunately the traditional module namespaces doesn't work well
either --they can't handle aliasing of built-in methods and the double
module inclusion problem means it won't work for modules either.

Ruby really needs some fixing in this area!

To clarify the problem a faux example:

  module Facets
  module Comparable
    alias_method :gte, :>= # no method to alias
    def ccc; "ccc"; end
  end
  end

  module Comparable
    include Facets::Comparable
  end

  10.ccc #=> NoMethodError

T.

···

On Mar 1, 4:40 pm, "Elliott Hird" <penguinoftheg...@googlemail.com> wrote:

On 01/03/2008, Trans <transf...@gmail.com> wrote:

> Given:

> class X
> def yo=x; @yo=x; end
> end

> class Y
> def yo!; puts @yo; end
> end

> x = X.new

> Is there any way to extend x with Y's functionality (without going
> back and changing the given code)? Eg.

> >> x.yo="Hello World"
> >> x.yo!
> Hello World

> T.

class << x; Y.instance_methods.each {|m| define_method m, Y.method(:m)}; end

kind of. brings in Object onwards, though, but that's easy to fix.