From: Alex Stahl <astahl@...5.com>
Date: 2010-11-11T15:45:29+09:00
Subject: Re: what's an object?

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Method class:  http://ruby-doc.org/core/classes/Method.html



________________________________________________________________________

Alex Stahl | Sr. Quality Engineer | hi5 Networks, Inc. | astahl@hi5.com
|

On Wed, 2010-11-10 at 23:55 -0600, timr wrote:

> On Nov 10, 5:50 pm, Eva <eva54...@sina.com> wrote:
> > I'm also switching from perl and php.
> > I'm not sure in ruby what's an object.
> > It seems each instance of a class is an object, is it?
> >
> > Thanks.
> 
> Classes are tables of defined behaviors (i.e. methods). An instance of
> a class is indeed an object, as you noted. When a message is sent to
> an object ("some string".upcase, "some string".reverse, "some
> string".split('') etc.), the object looks inside the class that
> instantiated it to see if it has the definition for that method. If
> not it looks higher up the class ancestry chain to find the
> definition. It may surprise you coming from perl and php that some
> very basic things are objects in ruby. For instance, integers are
> objects since they are instances of the Fixnum class and have an
> object_id.
> 
> Alex said everything is an object--including an instance of a class,
> the class itself, its methods. I agree up until he mention methods as
> objects. I don't think that can be demonstrated. For instance, we
> cannot get the object_id of a method. '+.object_id' doesn't work. So,
> I don't agree that methods are objects. Classes on the other hand, are
> instances of the Class class, and therefore, in a brain twisting way,
> are objects with object_ids.
> 
> Demonstration:
> Monkey = Class.new
> 
> #equivalent to
> #class Monkey; end
> 
> Monkey.class # => Class
> Monkey.object_id # => 2159398000
> 
> In addition to defining behavior, classes also can define state. The
> state is stored in instance variables. These concepts, defining the
> behavior and the state, are at the heart of object oriented
> programming.
> 

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