How do I validate that two values do not equal each other in a Rails model?

Question

I have a User model, which has an email and a password field. For security, these may not be equal to each other. How can I define this in my model?

Answer 1

it is much wiser to use custom validator, here is code for universal validator that can be used

class ValuesNotEqualValidator < ActiveModel::Validator
  def validate(record)
    if options[:fields].any? && options[:fields].size >= 2
      field_values = options[:fields].collect { |f| record.send(f) }
      unless field_values.size == field_values.uniq.size
        record.errors[:base] <<
            (options[:msg].blank? ? "fields: #{options[:fields].join(", ")} - should not be equal" :
                options[:msg])
      end
    else
      raise "#{self.class.name} require at least two fields as options [e.g. fields: [:giver_id, :receiver_id]"
    end
  end
end

and then use it like:

class User < ActiveRecord::Base
  # ...
  validates_with ValuesNotEqualValidator, fields: [:email, :password], msg: "This Person is evil"
end