From: Robert Klemme <shortcutter@...>
Date: 2007-03-16T00:45:08+09:00
Subject: Re: What does this do? :

On 15.03.2007 15:54, Stefano Crocco wrote:
> Alle gioved� 15 marzo 2007, jko170 ha scritto:
>> Looking at this piece of code, what does the colon do?
>>
>> def partner_to(user)
>>     raise ArgumentError unless user
>>     user.id == recipient_id ? sender : recipient
>>  end
>>
>> I got the code from this rails post:
>> http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/7fdccd
>> dde9b97ffc/6112294580b9e0ce?lnk=gst&q=internal+mail&rnum=1#6112294580b9e0ce
>>
>> I'm just asking because I've never seen the colon used before.
> 
> This is a shortcut for
> if user.id == recipient_id ? then sender
> else recipient
> end

You got a question mark too much in there. :-)

> What comes before the ? is the condition (not to confuse with the ? which ends 
> the name of predicate methods: array.empty? do_something : do_something_else 
> won't work, array.empty? ? do_something : do_something_else will), after 
> the ? and before the : there's the action to take if the condition is true 
> and after the : what to do if it's false.

Yes.

	robert