From: dblack@...
Date: 2007-02-06T08:39:10+09:00
Subject: Re: Code explanation requeted

Hi --

On Tue, 6 Feb 2007, Neville Franks wrote:

> Hi, Can someone please shed some light on the following code:
>
> ---
>  def test_listen
>    s = nil
>    log = Object.new
>    class << log; self end.__send__(:define_method, :to_int) {
>      s.close
>      2
>    }
>    inet_stream do |s|
>      assert_raise(IOError) {
>        s.listen(log)
>      }
>    end
>  end
> ---
>
> In particular the "class" statement and "self
> end.__send__(:define_method, :to_int)"
>
> Is this actually a class and where is its "end"?

It is a class; it's the singleton class of log.  You may join the club
of people who want a singleton_class method :-)  That would make it:

   log.singleton_class.__send__(:define_method, :to_int) ...

As it stands, in order to address the singleton class as an object,
you have to capture it through the technique of:

   class << log
     self
   end

What you're seeing in the code you've got is this, but strung together
on one line without much to help you parse it visually if you don't
already know what to expect.  I would tend to write it as:

   (class << log; self; end).__send__  etc.


David

-- 
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