Rails validation method comparing two fields?

Question

My model has two fields that i want to compare to each other as part of the validation. I want to be sure end_time is after start_time. I have written a validation method to compare them, but I must be doing something wrong, because the values are always nil. Can someone help?

class LogEntry < ActiveRecord::Base
  validates :start_time, :presence => { :message => "must be a valid date/time" }
  validates :end_time, :presence => {:message => "must be a valid date/time"}
  validate :start_must_be_before_end_time

  def start_must_be_before_end_time
    errors.add(:start_time, "must be before end time") unless
       start_time > end_time
  end 
end

gets the error

undefined method `>' for nil:NilClass

So, start_time and/or end_time are nil. I thought I was following the many examples I found, but apparently not. What am I missing?

Thanks.

user_2483313 · Answer

Ruby on Rails 7.0 supports validates_comparison_of like this

validates :start_time, comparison: { less_than: :end_date }

Rails validation method comparing two fields?

6 Answers