From: Tim Hunter Date: 2007-08-14T20:26:45+09:00 Subject: Re: Symbols and strings maghac wrote: > On Aug 14, 11:11 am, "Robert Dober" wrote: > >> On 8/14/07, maghac wrote: >> >> >>> Hi, >>> as a long-term perl user just recently converted to ruby, I'm curious >>> about one particular syntax "feature": ruby symbols and how they >>> relate to strings. >>> >>> Isn't really :name a shortcut for "name"? (I read somewhere in an >>> explanation of attr_reader that e.g :age was the "name" of the >>> variable age, while age is the actual content of that variable). If >>> so, couldn't you use this in hash keys as well, e.g say hashvar[:key] >>> instead of hashvar['key']. >>> >>> Are there situations where you cannot use symbols instead of strings, >>> or the other way around? >>> >>> I might be too used to the way strings and barewords are handled in >>> perl (if something looks like a string, and it's not a function call, >>> it's interpreted as a string. This means you can say $hashvar{key} >>> without quoting the key). >>> >> This question is asked very frequently, please search the archives for >> more info. >> I will try to give a very quick answer nevertheless: >> >> Symbols are immutable, thus great to represent immutable data, often >> that makes them an excellent choice for hash keys >> { :the_value => 42, :alternatively => 22, :or_even => 101010 } >> they just do not play the role of Strings, coming from Perl you just >> had to use Strings, you did not have a tool for names (wait a moment >> was there not such a thing as references to constants?). >> Very roughly put I see Symbols as name, and Strings as data, whenever >> I can use Symbols I use them, comes natural after some time. >> >> HTH >> Robert >> -- >> [...] as simple as possible, but no simpler. >> -- Attributed to Albert Einstein >> > > Thanks, that cleared a few things for me. > > I found something in the FAQ about it, but it didn't really answer my > question on the differences/similiarities between symbols and strings. > > thanks > Magnus > > > Don't make more out of this than there is. A symbol is a kind of literal in Ruby. It's the name of a number. You pick the name, Ruby picks the number. Ruby guarantees that whenever you use the symbol in your program it will always refer to the same number. That's it. That's all there is. Really. Given a symbol, you can retrieve its name in the form of a string with the #to_s method. You can convert a string (or almost any sequence of characters, for that matter) to a symbol with the #to_sym method. Most methods that accept symbol arguments, like attr_reader and kin, accept strings as well. All attr_reader does with your symbol is use its name as the name of the attribute. -- RMagick OS X Installer [http://rubyforge.org/projects/rmagick/] RMagick Hints & Tips [http://rubyforge.org/forum/forum.php?forum_id=1618] RMagick Installation FAQ [http://rmagick.rubyforge.org/install-faq.html]