gem 'validates'

validates :attribute, <validator_underscore>: true

class User < ActiveRecord::Base
  validates :email, :email => true
  validates :site, :url => true, :allow_blank => true
end

class Company < ActiveRecord::Base
  # note AssociationLengthValidator is inherited from ActiveModel::Validations::LengthValidator
  # http://api.rubyonrails.org/classes/ActiveModel/Validations/LengthValidator.html
  # so you can easily use standard options like :is, :minimum, :maximum, etc.

  validates :employees,
  :association_length => {
    :minimum => 1,
    :select => ->(employee) { employee.name.in? ["Mike", "John"] }
  }

  validates :employees, :association_length => { :minimum => 1, :select => :employees_filter }

  def employees_filter(employees)
    employees.select { |employee| employee.name.in? ["Mike", "John"] }
  end
end

class Page < ActiveRecord::Base
  validates :slug, :slug => true
end

class Content < ActiveRecord::Base
  # Validates URI component.
  # URI component must be of the following type:
  # :ABS_URI, :REL_URI, :URI_REF, :ABS_URI_REF, :REL_URI_REF, :ESCAPED, :UNSAFE, :SCHEME,
  # :USERINFO, :HOST, :PORT, :OPAQUE, :REGISTRY, :ABS_PATH, :REL_PATH, :QUERY or :FRAGMENT.
  # These types are provided URI library. For more info see URI::DEFAULT_PARSER.regexp.

  validates :path, :uri_component => { :component => :ABS_PATH }
end