AttrValidator Build Status Code Climate

AttrValidator is simple library for validating ruby objects. The main idea of the gem is separate all object validation logic from the object itself


Lets say you have the following class and you wan to validate objects of this class

class Contact
  attr_accessor :first_name, :last_name, :position, :age, :type, :email, :color, :status, :stage, :description, :companies

To validate objects of the Contact class define a validator:

class ContactValidator
  include AttrValidator::Validator

  validates :first_name, presence: true, length: { min: 4, max: 7 }
  validates :last_name,  length: { equal_to: 5 }
  validates :position,   length: { not_equal_to: 5 }
  validates :age,        numericality: { greater_than: 0, less_than: 150 }
  validates :type,       numericality: { greater_than_or_equal_to: 1, less_than_or_equal_to: 5 }
  validates :email,      email: true
  validates :color,      regexp: /#\w{6}/
  validates :status,     inclusion: { in: [:new, :lead] }
  validates :stage,      exclusion: { in: [:wrong, :bad] }

  validate_associated :companies, validator: CompanyValidator

  validate :check_description

  def check_description(entity, errors)
    if entity.description.nil?
      errors.add(:description, "can't be empty")

Instantiate the validator and pass a contact object inside:

errors =

errors is a hash which contains all validation errors if object is valid then errors will be empty

Adding own validators

AttrValidator can be extended by adding your own validators. To add a validator define a class with two the class method validate and validate_options: The following example demonstrates the built in inclusion validator, it validates that specified value is one of the defined value

class AttrValidator::Validators::InclusionValidator

  # Validates that given value inscluded in the specified list
  # @param value [Object] object to validate
  # @parm options [Hash] validation options, e.g. { in: [:small, :medium, :large], message: "not included in the list of allowed items" }
  #                      where :in - list of allowed values,
  #                      message - is a message to return if value is not included in the list
  # @return [Array] empty array if object is valid, list of errors otherwise
  def self.validate(value, options)
    return [] if value.nil?

    errors = []
    if options[:in]
      unless options[:in].include?(value)
        errors << (options[:message] || AttrValidator::I18n.t('errors.should_be_included_in_list', list: options[:in]))

  # Validates that options specified in
  # :inclusion are valid
  def self.validate_options(options)
    raise ArgumentError, "validation options should be a Hash" unless options.is_a?(Hash)
    raise ArgumentError, "validation options should have :in option and it should be an array of allowed values" unless options[:in].is_a?(Array)


And register it in AttrValidator:

AttrValidator.add_validator(:inclusion,    AttrValidator::Validators::InclusionValidator)

Now you can use it:

class SomeValidator
  include AttrValidator::Validator

  validates :size, inclusion: { in: [:small, :medium, :large] }


Add this line to your application's Gemfile:

gem 'attr_validator'

And then execute:

$ bundle

Or install it yourself as:

$ gem install attr_validator


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request


  1. Document methods


Albert Gazizov, @deeper4k