gem install validatable

Validation of an entire hierarchy of objects with errors aggregated at the root object.

class Person
  include Validatable
  validates_presence_of :name
  attr_accessor :name
end

class PersonPresenter
  include Validatable
  include_validations_for :person
  attr_accessor :person

  def initialize(person)
    @person = person
  end
end

presenter = PersonPresenter.new(Person.new)
presenter.valid? #=> false
presenter.errors.on(:name) #=> "can't be blank"

Validations that turn off after X times of failed attempts.

class Person
  include Validatable
  validates_presence_of :name, :times => 1
  attr_accessor :name
end

person = Person.new
person.valid? #=> false
person.valid? #=> true

Validations can be given levels. If a validation fails on a level the validations for subsequent levels will not be executed.

class Person
  include Validatable
  validates_presence_of :name, :level => 1, :message => "name message"
  validates_presence_of :address, :level => 2
  attr_accessor :name, :address
end

person = Person.new
person.valid? #=> false
person.errors.on(:name) #=> "name message"
person.errors.on(:address) #=> nil

Validations can also be given groups. Groups can be used to validate an object when it can be valid in various states. For example a mortgage application may be valid for saving (saving a partial application), but that same mortgage application would not be valid for underwriting. In our example a application can be saved as long as a Social Security Number is present; however, an application can not be underwritten unless the name attribute contains a value.

class MortgageApplication
	include Validatable
	validates_presence_of :ssn, :groups => [:saving, :underwriting]
	validates_presence_of :name, :groups => :underwriting
	attr_accessor :name, :ssn
end

application = MortgageApplication.new
application.ssn = 377990118
application.valid_for_saving? #=> true
application.valid_for_underwriting? #=> false

As you can see, you can use an array if the validation needs to be part of various groups. However, if the validation only applies to one group you can simply use a symbol for the group name.

Similar to Rails, Validatable also supports conditional validation.

class Person
	include Validatable
	attr_accessor :name
	validates_format_of :name, :with => /.+/, :if => Proc.new { !name.nil? }
end
Person.new.valid? #=> true

Validatable also exposes an after_validate hook method.

class Person
	include Validatable
	validates_presence_of :name
	attr_accessor :name
end

class ValidatesPresenceOf
	after_validate do |result, instance, attribute|
	            instance.errors.add("#{attribute} can't be blank") unless result
	    end
end

person = Person.new
person.valid? #=> false
person.errors.on(:name) #=> "name can't be blank"

The after_validate hook yields the result of the validation being run, the instance the validation was run on, and the attribute that was validated

In the above example the attribute "name" is appended to the message.