Basic question about Ruby's class hierarchy

ruby-talk
1

Hi,
I thought I understood this, but apparently not.

What is this object exactly?
o = class << String; self; end

p o
and
p String
should output the same thing.

but it doesn't
p o #<Class:String>
p String #String

Thanks for answering such a basic question for me.
  -Patrick

···

From my understanding:
--
Posted via http://www.ruby-forum.com/.

2

o is not the same as String. o is String's metaclass. The exact role
that metaclasses play is Ruby's take on object-oriented programming is
too much for an answer post such as this. But you might want to read
why's explanation at:

    http://www.whytheluckystiff.net/articles/seeingMetaclassesClearly.html

Eric

···

On Aug 10, 11:22 pm, Patrick Li <patrickli_2...@hotmail.com> wrote:

I thought I understood this, but apparently not.

What is this object exactly?
o = class << String; self; end

From my understanding:
p o
and
p String
should output the same thing.

but it doesn't
p o #<Class:String>
p String #String

====

Rails training and Ruby training available at http://LearnRuby.com .
On-site and customized training are available.

3

In your example, String is an instance of Class, and o is the
eigenclass (or metaclass) of String. Maybe this will help clarify:

  o = class << String; self; end
  o.class_eval do
    def backwards
      'gnirtS'
    end
  end

  String.backwards # => "gnirtS"

HTH,
Chris

···

On Aug 10, 9:22 pm, Patrick Li <patrickli_2...@hotmail.com> wrote:

Hi,
I thought I understood this, but apparently not.

What is this object exactly?
o = class << String; self; end

From my understanding:
p o
and
p String
should output the same thing.

but it doesn't
p o #<Class:String>
p String #String

Thanks for answering such a basic question for me.
-Patrick
--
Posted viahttp://www.ruby-forum.com/.