From: Eric Mahurin <eric_mahurin@...>
Date: 2005-06-09T22:46:29+09:00
Subject: Re: making a duck

--- nobuyoshi nakada <nobuyoshi.nakada@ge.com> wrote:

> Hi,
> 
> At Thu, 9 Jun 2005 01:30:53 +0900,
> Eric Mahurin wrote in [ruby-talk:144892]:
> > # make == look like ===
> > digit = (?0..?9).duck(:==,:===)
> > # match to a string of 4 digits
> > # Proc responds to [] like a String/Array
> > cursor.scan(proc{|i|(i<4)? digit : nil}) 
> 
> It would be called as `alias', I guess.
> 
> -- 
> Nobu Nakada

I don't care too much what the method names are.  Below is the
implementation I was thinking.  This gives you 3 ways to make a
"duck" (a minimal object for a duck-typed argument of a
method):

digit = (?0..?9).duck(:==,:include?,:to_s,:inspect)
alpha = Object.duck(size: proc{26}, :== =>
(?a..?z).method(:===) )
test = Object.duck(:hi) {puts "hello world!"}

Any chance of getting something like this in the standard lib? 
Your "Behavior" implementation is fine too.


class Object
    def duck(*new_old)
        obj = Object.new
        klass = (class<<obj;self;end)
        until new_old.empty?
            new,old = new_old.slice!(0,2)
            klass.send(:define_method,new,&self.method(old))
        end
        obj
    end
    def self.duck(methods,&block)
        obj = self.new
        klass = (class<<obj;self;end)
        if block
            klass.send(:define_method,methods,&block)
        else
            methods.each { |name,proc|
                klass.send(:define_method,name,&proc)
            }
        end
        obj
    end
end



		
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