From: Robert Klemme <shortcutter@...>
Date: 2011-04-16T22:30:37+09:00
Subject: Re: looking for an "inversion" pattern

On 15.04.2011 17:40, Fearless Fool wrote:
> Thanks everybody!!

You're welcome!

>> I am sorry, I still do not understand your motivation to have a class
>> method which receives an instance as first argument.
>
> My motivation is that I was writing a lot of code like this:
>
> module HasXattr
>      def xattr_reference(key);  Xattr.xattr_reference(self, key); end
>      def xattr_store(key, value); Xattr.xattr_store(self, key, value);
> end
>      def xattr_has_key?(key); Xattr.xattr_has_key?(self, key); end
>      def xattr_delete(key); Xattr.xattr_delete(self, key); end
>      ...
> end
>
> .. and I thought to myself: this is Ruby.  There must be a better way.
> I guess I should have shown this concrete example earlier in the thread.

With my code you could do

module HasXattr
   def xattr # foo in your lingo
     proxy(Xattr)
   end
end

or directly use it in your class

module HasXattr
   def xattr # foo in your lingo
     proxy(Xattr)
   end
end

Then you can do

obj.xattr.has_key? "k"

or

obj.xattr.tap |x|
   x.store "k", "v" unless x.has_key?
end

Btw, what is Xattr?  Where does it come from and what does it do?  From 
the looks it seems to be some external storage for attributes associated 
with your instance which you do not want to store in the instance itself 
(for whatever reasons).  What do you need that for?

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/