From: Bill Barnhill <xmlarchitect@...>
Date: 2006-03-14T23:03:18+09:00
Subject: Re: [RCR] abstract method in Ruby

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Oops, my apologies, forgot an end in example.
Should read
class B < A
    def initialize
       @a =3D "foo"
    end
end

Another though on this is that it would allow us to define message
interfaces (aka duck-typing prototypes).

--Bill

Bill Barnhill
i-name: xri://=3DBill.Barnhill (For more info:
http://2idi.com/grs/index.php?referral_code=3Dcommunitivity
)

On 3/14/06, Bill Barnhill <xmlarchitect@gmail.com> wrote:
>
> Hmm, just some thoughts.
> I think the abstract method idea nice in concept, but implementation
> perhaps too Java-ish.
>
> If I get a chance later this week I'll code this, but for now here's how
> I'd envision something like this within Ruby code:
>
> class A
>     should_respond_to_behavior  #..options hash describing what to do if
> msg not
>                                                # responded to properly
> goes here,
>                                                # nice to support YAML as
> well..
>     should_respond_to :foo, :bar =3D> {}, :baz =3D> {:param_count =3D> 3}
> end
>
> class B < A
>     def initialize
>        @a =3D "foo"
> end
>
> B.new
> =3Dbegin
> At this point the class a checks responses:
> .. it expects a response to messages :foo and :bar with any or no params
> .. it expects a response to baz with three params
> .. raises exception if either check fails, or logs, depending on
> configuraiton
>
> You could extend the above by having behavior contrained to
> normative language...
> .. should_respond_to  just logs warning if msg not responded to properly
> .. must_respond_to  raises exception if msg not responded to properly
>
> Even the following, though HTBD (Here there be dragons..i.e. I'm a little
> quesy about this last one)
> .. may_respond_to
> Same syntax as above, but means that any instances can only respond to th=
e
> defined messages. I can see several uses for this, but also see several
> misuses and implementing so you could be reasonably sure about constraint
> would be a pain, and might have to be in Ruby internals. This behavior al=
so
> doesn't match normative language use, perhaps a
> .. must_only_respond_to
>
>
> --Bill
>
> Bill Barnhill
> i-name: xri://=3DBill.Barnhill (For more info: http://2idi.com/grs/index.=
php?referral_code=3Dcommunitivity
> )
>
>
>
> On 3/13/06, nobu@ruby-lang.org <nobu@ruby-lang.org> wrote:
> >
> > Hi,
> >
> > At Tue, 14 Mar 2006 01:01:31 +0900,
> > ara.t.howard@noaa.gov wrote in [ruby-talk:183918]:
> > > hmmm - but that (both actually) fails here:
> > >
> > >      harp:~ > cat a.rb
> > >      class Module
> > >        def abstract_method m
> > >          define_method(m) do |*a|
> > >            defined?(super) ? super : raise(NotImplementedError, m)
> > >          end
> > >        end
> > >      end
> > >
> > >      class A
> > >        def foo; 42; end
> > >      end
> > >      class B < A
> > >        abstract_method "foo"
> > >      end
> > >
> > >      p B::new.foo
> > >
> > >
> > >      harp:~ > ruby a.rb
> > >      42
> >
> > Simply separate Module#abstract_method and Class#abstract_method.
> >
> >      class Class
> >        def abstract_method m
> >          define_method(m) do |*a|
> >            raise(NotImplementedError, m)
> >          end
> >        end
> >      end
> >
> > --
> > Nobu Nakada
> >
> >
>

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