Helper method to check validation errors

check_validation_details.rb

# required: Rails 5 or active_model-errors_details gem
# see: https://cowbell-labs.com/2015-01-22-active-model-errors-details.html
module CheckValidationDetails
  # Check if the given error exists on given attribute
  #
  # @param attribute [Symbol] model attribute
  # @param error [Symbol] machine-friendly error name
  # @return [Boolean] whether or not any given error exists
  def error?(attribute, error)
    errors.details.key?(attribute) && errors.details[attribute].any? { |err| err[:error] == error }
  end
end