From: Brian Candler <b.candler@...>
Date: 2009-05-26T02:30:19+09:00
Subject: Re: hash assignment [:x] vs ['x']

Mk 27 wrote:
> Being totally new to ruby, I just noticed that using
> 
> bob['phone']
> 
> which coming from perl is a style I'm used to, results in a separate key
> than
> 
> bob[:phone]
> 
> That seems slightly weird, I had assumed the :form is just a shorthand
> like %w(  ).  So -- is there anything more that I need to understand
> about this distinction?

Yes. :phone is a Symbol literal, whereas 'phone' is a String literal.

Symbols and Strings are two different types of object entirely. In 
particular:

* Symbols are immutable

* a literal like :foo will always give exactly the same object instance 
throughout the lifetime of the program, whereas a string literal like 
'foo' will give a fresh object every time it is used

For this reason, symbols are somewhat more efficient for hash lookups. 
Some libraries use them for passing hashes of options, although I 
suspect this is more because they are one character shorter to type, 
rather than any particular performance reason :-)
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