Localized EachValidator

LocalizedEachValidator is a small abstract subclass of ActiveModel::EachValidator that makes it easy to write validators whose error messages are looked up through Rails / ActiveModel's I18n infrastructure.

Subclass LocalizedEachValidator, declare an error_key, and implement #valid?. The validator adds the error key to the record's errors when a value fails validation; ActiveModel will then resolve that key against the standard I18n error message hierarchy.

Add to your Gemfile:

gem "localized_each_validator"

Or, if you're writing your own validator gem, add it to your gemspec:

spec.add_dependency "localized_each_validator", "~> 2.0"

Then run bundle install.

Subclass LocalizedEachValidator, set an error_key, and implement #valid?:

class FourValidator < LocalizedEachValidator
  error_key :must_be_four

  def valid?(record, attribute, value)
    value == 4
  end
end

Users of your validator can then add a translation:

en:
  activemodel:
    errors:
      messages:
        must_be_four: "must be four"

LocalizedEachValidator honors the standard EachValidator options:

• :allow_nil — skip validation when the value is nil.
• :allow_blank — skip validation when the value is blank.
• :message — override the default error_key-based error message with a literal string or another symbol.

If you don't call error_key, the default is derived from the class name: the trailing Validator is stripped, the result is demodulized, and underscored. For example, Auth::EmailAddressValidator defaults to :email_address.

See the LocalizedEachValidator class documentation for more details.