From: Stefano Crocco <stefano.crocco@...>
Date: 2011-08-28T17:19:20+09:00
Subject: Re: Help me understand this code

On Sunday 28 August 2011 17:08:46 Chris Root wrote:
> Can anyone explain the syntax for the following code? It worked in rails
> 3.1/1.9.2 but fails to work in 2.3.4/1.8.7. It's defined in a model if
> it pertains. Many thanks.
> 
> digital? ? :digital : :real

It's a shorter form for

if digital? then :digital
else :real
end

This general form of this expression is:

a ? b : c

The part before the question mark (note that in your code the first question 
mark one is part of the method name a it has no special meaning) is the 
condition; the part between the question mark and the column is the value to 
return if the condition evaluates to true and the part after the colon is the 
value to return if the condition evaluates to false.

I don't know rails so I can't say what has changed between rails versions to 
make it stop working. I don't think there were changes in ruby from 1.8 to 1.9 
affecting this construct. Also, what do you exactly mean by "fails to work"? 
Does it produce an error (in which case you should post the error message to 
help people understand what may be going on), or does it just give unexpected 
results?

I hope this helps

Stefano