Question

What is the best way to write this calculation in Ruby?

amt = self.alt_inv - (self.alt_tax ? self.alt_tax : 0)
    - (self.alt_freight ? self.alt_freight : 0)
    - (self.misc1_amt ? self.misc1_amt : 0)
    - (self.misc2_amt ? self.misc2_amt : 0)

Answer 1

In Ruby, if something is not nil, it will return true in a boolean expression and its value in a calculation.

I’m not explaining it really well, but you can do something like this:

amt = alt_inv - 
  (alt_tax     || 0) -
  (alt_freight || 0) -
  (misc1_amt   || 0) -
  (misc2_amt   || 0)

This is a more concise way of doing the ternary you were originally using.

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Edit:

I actually like Jed Schneider’s answer better than my own. I’ll not copy it here, since his answer deserves the upvote for its elegance.