Help me understand this code

ruby-talk
1

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

···

--
Posted via http://www.ruby-forum.com/.

2

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

···

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

3

That's a ternary operator, it works like Stefano said. It isn't broken,
whatever code was using it must be broken.

···

On Sun, Aug 28, 2011 at 3:08 AM, Chris Root <chrisr1386@gmail.com> 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

--
Posted via http://www.ruby-forum.com/\.

4

Perfect. Thank you

···

--
Posted via http://www.ruby-forum.com/.

5

And the way we can figure that out is with an error message.

I'm surprised that programmers still do this:

"It worked in rails 3.1/1.9.2 but fails to work in 2.3.4/1.8.7."

WTF does "worked" and "fails to work" mean in this context? Does it crash? (If
so, is there a stacktrace?) Does it do something other than what you expect?
Does it cause a unit test to fail? etc etc...

···

On Sunday, August 28, 2011 06:41:54 AM Josh Cheek wrote:

On Sun, Aug 28, 2011 at 3:08 AM, Chris Root <chrisr1386@gmail.com> 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
>
> --
> Posted via http://www.ruby-forum.com/\.

That's a ternary operator, it works like Stefano said. It isn't broken,
whatever code was using it must be broken.