unless

An unless evaluates the then branch if its condition is falsey, and evaluates the else branch, if there’s any, otherwise. That is, it behaves in the opposite way of an if:

  1. unless some_condition
  2.   expression_when_falsey
  3. else
  4.   expression_when_truthy
  5. end
  7. # The above is the same as:
  8. if some_condition
  9.   expression_when_truthy
  10. else
  11.   expression_when_falsey
  12. end
  14. # Can also be written as a suffix
  15. close_door unless door_closed?