Rails validation error messages: Displaying only one error message per field

Question

Rails displays all validation error messages associated with a given field. If I have three validates_XXXXX_of :email, and I leave the field blank, I get three

Answer 1

My monkey patch of ActiveModel::Errors class lib/core_ext/rails/active_model/errors.rb (I use this code for Ruby on Rails 5.0 release):

module ActiveModel
  class Errors

    # don't add an attribute's error message to details
    # if it already contains at least one message

    alias_method :old_add, :add

    def add(attribute, message = :invalid, options = {})
      if details[attribute.to_sym].size.zero?
        old_add(attribute, message, options)
      end
    end

  end
end

Create a file config/initializers/core_ext.rb and add a require core_ext/rails/active_model/errors.rb to it.