From: firstname@... (Hans Fugal)
Date: 2003-12-16T01:06:59+09:00
Subject: Re: Subclassing Array

With a slight modification what you offered would work:

class SimilArray
    def initialize(ary)
	@ary=ary
    end
    include Notifier
    def method_missing(:method,*args,&blk)
	@ary.send(:method,*args,&blk)
	notify # this is what's different
    end
end

But it would always notify even on read-only operations, and so it's
wasteful. But I could check by name for writing operations.

Another approach would be a mixin that provides the Array operations based
on [], []=, and <=> (for example). Is there such a beast? Maybe I should
just use Enumerable and to_a?

> BTW, do you know that an observer module already exist in the standard
> ruby lib ?
Yeah, but it is callback-based, but I would like mine to be proc-based.
e.g.

Observable way:
class MyObservable
    include Observable
    attr_reader :foo
    def foo=(o)
	@foo = o
	changed
	notify_observers(self)
    end
end
class MyObserver
    def initialize
	MyObservable.new.add_observer(self)
    def update(o)
	puts o.foo
    end
end

Notifier way:
class MyObservable
    include Notifier
    attr_reader ;foo
    def foo=(o)
	@foo = o
	notify
    end
end
class MyObserver
    def initialize
	o = MyObservable.new
	bar = "bar"
	o.add_notification { puts "#{o.foo} #{bar}" }
    end
end
 
My Notifier module is based on
http://www.rubygarden.org/ruby?ObserverPattern

-- 
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