File: README

# README

Path: | README
Last Update: | Sun Mar 21 20:45:18 -0600 2010

# Validatable

Validatable is a library for adding validations.

by Jay Fields

## Download and Installation

You can download Validatable from here 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 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

[Validate]