From: Kirk Haines <khaines@...>
Date: 2005-12-31T05:29:23+09:00
Subject: Re: What is the difference between :foo and "foo" ?

On Friday 30 December 2005 1:03 pm, Austin Ziegler wrote:

> Please edit your guide, as it is *not* correct when it says:
>
>    A Ruby symbol is a thing that has both a number (integer) and a string.
>
> This is not correct in any way. If you leave it as "A Ruby Symbol is a
> thing", you're fine. But when you say that it "has" a number and a
> string, you are incorrect. Symbols are not composed of the integer or
> string values that you can convert Symbols to; they just are. The
> value of a Symbol is not its String value or its Fixnum value, but
> itself.

I think that I am probably the source for this confusion, and I am guilty of 
not clarifying further what I meant.

:foo is a symbol.  The string representation of :foo is 'foo'.

:foo.to_s

:foo also has an integer that id, found with #object_id:

:foo.object_id

This is no different than any other object.  What is different is this:

irb(main):001:0> 'foo'.object_id
=> -609482574
irb(main):002:0> 'foo'.object_id
=> -609486184
irb(main):003:0> 'foo'.object_id
=> -609489724

The id changes because each 'foo' is a different object.

irb(main):004:0> :foo.object_id
=> 3957006
irb(main):005:0> :foo.object_id
=> 3957006
irb(main):006:0> :foo.object_id
=> 3957006

The id doesn't change because :foo is just :foo -- it's the same object every 
time.


Kirk Haines