From: Sam Roberts <sroberts@...>
Date: 2005-03-17T11:29:14+09:00
Subject: Re: Symbol vs String

Quoting jim@weirichhouse.org, on Thu, Mar 17, 2005 at 11:08:59AM +0900:
> On Wednesday 16 March 2005 03:37 pm, Sebesty�n G�bor wrote:
> > Just a dumb question: what is the real difference between { :aKey =>
> > "aValue" } and { "aKey" => "aValue" } ? I know the first key is a
> > symbol the latter is a string. I like string keys why should I use
> > symbols? Why symbols worth to use as keys?
> 
> Use Strings for their content.  Use Symbols for their arbitrary uniqueness.

I used to do this, but ran into problems.

Symbols are great for things related to ruby becuase the :bar form for symbol
literals accepts the same kind of chars as ruby identifiers. I use them be
preference in interacting with ruby's meta-programming APIs.

They start to fall down outside of this. For example, I tried to use
with mime types:

  :text
      ==>:text
  :video
      ==>:video
  :octet-stream
  NameError: undefined local variable or method `stream' for main:Object
          from (irb):3
  'octet-stream'.intern
      ==>:"octet-stream"

You CAN use them for things outside of the domain of ruby names, but it gets
painful if the names of those things are arbitarily unique, but have "-"
characters in their name, you first have to create a String!

You can get around this by creating constants:

  OCTETSTREAM = 'octet-stream'.intern
  TEXT = :text

etc., but that might not fit your API goals very well.

Anyhow, I moved back to using strings instead of symbols. The need to create a
string and intern it for things that are logically symbols but have a "-" in
them was too painful.

That was my experience, anyhow.

Cheers,
Sam