Question

I’m fairly new to ruby on rails. I’m using ruby 1.9.3 and rails 3.2.6. My model contains Pilots which have many Checkins. I am trying to add some validation to my model such that a pilot may not add a new checkin which matches the last checkin that pilot made.

class Checkin < ActiveRecord::Base
    belongs_to :pilot

…

  validate :must_not_match_last_checkin

  def ==(comparison_checkin)
    self_compare_id = checkin_compare_id self
    comparison_compare_id = checkin_compare_id comparison_checkin

    if self_compare_id != comparison_compare_id
      return true
    else
      return false;
    end

  end

  private

  def must_not_match_last_checkin
    if self == self.pilot.checkins.last
      errors.add(:base, "Checkin is only valid if it differs from your previous checkin")
    end
  end 

  def checkin_compare_id checkin
    diff = ""

    if !checkin.nil?
      diff = checkin.location + checkin.description
    end

    return diff
  end
end

I’ve tested the custom equality method in other situations and it appears to work fine. However when I use the above model the model error always occurs even if the description/location is different.

Answer 1

In your comparison operator:

if self_compare_id != comparison_compare_id

should really be

if self_compare_id == comparison_compare_id