Question

I’m pretty new to Ruby and Rails but even after searching stack overflow and google I couldn’t find an answer to this.

I’ve got a simple Ruby shorthand if statement that should return an integer like so:

# in the context of this erb document `amount` is defined as 5.
@c = ( defined? amount ? amount : r( 1,4 ) )

r() is a custom helper function that returns a random number between in this case 1 and 4.

The way I intend this to work is that if amount is defined, then use the number defined as amount, else generate a random number between 1 and 4 and use that instead.

When printing out @c however Ruby outputs expression rather than a number.

What do I have to do to get this working as I intended and what am I doing wrong?

Many thanks for reading!

Answer 1

defined? is binding to amount ? amount : r(1,4) so it is equivalent to:

defined?(amount ? amount : r(1,4))

You probably want:

defined?(amount) ? amount : r(1,4)

Actually, odds are that amount || r(1,4), or amount.nil? ? r(1,4) : amount would better match what you want, since I think you don’t want this:

1.9.3p194 :001 > defined?(amount)
 => nil 
1.9.3p194 :002 > amount = nil
 => nil 
1.9.3p194 :003 > defined?(amount)
 => "local-variable" 

…in which case @c would be nil – the value of the defined variable.