Understanding Rails Callbacks & Common Pitfalls

Thank you so much for sharing such useful tips. One point: you have a tiny typo in Comapny.find_by!(name:...), - it should be Company, I suppose :).

Also in the Brake#do_brake method, I don't think the call puts "Brake id: #{self.brake.id}" to correct, - you are calling brake on the instance of the Brake class instead of just calling id method.