From: Hal Fulton <hal9000@...>
Date: 2005-03-17T12:02:19+09:00
Subject: Re: Symbol vs String

Sam Roberts wrote:
> 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.

I believe you can do things like :"octet-stream"  -- but I grant
that is not much better.


Hal