From: Dave Grijalva <grijalva@...>
Date: 2007-05-30T08:06:58+09:00
Subject: Re: Symbols vs. Strings

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I think the second point that Emilio was making is the more important one.
Let me try to clarify:

irb(main):008:0> puts "foo".object_id
1724824
=> nil
irb(main):009:0> puts "foo".object_id
1708744
=> nil
irb(main):010:0> puts :foo.object_id
3678478
=> nil
irb(main):011:0> puts :foo.object_id
3678478


You can see here that a new String object is created every time you use a
literal string.  With a symbol, however, you are re-using the same object
anywhere you use a symbol with the same name.  Using symbols can save you a
lot of resources, both processor time and memory.

-dave

On 5/29/07, Emilio Tagua <miloops@gmail.com> wrote:
>
> On 5/29/07, John Blanco <zablanc@yahoo.com> wrote:
> > I'm new to Ruby, but coming up to speed quickly.  One question I still
> > have never seen a good explanation to is this: When is it preferred to a
> > key a hash with a symbol, and when is it keyed by string?  Is this just
> > personal preference, or is there a rule of thumb?
> >
> > For example, in the Rails book, the session variable is always populated
> > with symbols, i.e.:
> >
> > session[:user] = User.new
> >
> > It's also obviously completely common throughout the Rails framework
> > (e.g., :controller =>, :action =>, etc.)
> >
> > So, when should I use what...or what should I prefer?
>
> Symbols are ligh-weight, they don't have so much methods to initialize
> has strings:
>
> irb(main):009:0> :asd.methods.size
> => 45
> irb(main):010:0> "asd".methods.size
> => 143
>
> So thats why you use it in params or other places when you just need
> the name. Also a difference is that a symbol :sym is :sym everywhere,
> but a string "string" -only the string, not assigned to a variable- is
> a different refence to a String object  each time you write "string" .
>
> Those are the most important diferences IMO. Sorry if i wasn't that clear
> tho.
>
> Cheers
>
>

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