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Validatable is a library for adding validations.
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README

= Validatable

Validatable is a library for adding validations.

by Jay[http://jayfields.blogspot.com] Fields[http://jayfields.blogspot.com]

== Download and Installation

You can download Validatable from here[http://rubyforge.org/projects/validatable] or install it with the following command.

 $ gem install validatable

== License
 	
You may use, copy and redistribute this library under the same terms as Ruby itself (see http://www.ruby-lang.org/en/LICENSE.txt).

== Examples

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.

See the tests for more examples

== Contributors
Rick Bradley, Anonymous Z, Jason Miller, Ali Aghareza, Xavier Shay, Dan Manges, Karthik Krishnan and Venkat, Clint Bishop, Chris Didyk, Yi Wen
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