ActiveModel Interdependence

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Specify that validations depend on the validation of other fields

Lets classes that implement ActiveModel::Model or ActiveModel::Validator specify that they are dependent on other fields being valid. These specifications are translated into a dependency graph, sorted, and applied in order to a model. As a result, fields are only validated once the fields that they depend on are validated.


Simply run shell gem install activemodel-interdependence

or add activemodel-interdependence to your gemfile

ruby gem 'activemodel-interdependence'

and run bundle install from your shell.


```ruby class DayValidator < ActiveModel::EachValidator validates :month_field, inclusion: 1..12 validates :year_field, inclusion: 0..2015

def validate_each(record, attribute, value) month = dependency(record, :month_field) year = dependency(record, :year_field)

return if (1..Time.days_in_month(month, year)).cover?(value)
record.errors[attribute] << "is not valid for the month #{Date::MONTHNAMES[month]}"   end

def dependency(record, proxy_name) name = options.fetch(:dependencies, {}).fetch(proxy_name)

record.send(name)   end end

class Birthday include ActiveModel::Model attr_accessor :day, :month, :year

validates :day, day: { dependencies: { month_field: :month, year_field: :year } } end

leap_day = 29, month: 2, year: 2000) leap_day.valid? # => true

not_a_leap_day = 29, month: 2, year: 1999) not_a_leap_day.valid? # => false not_a_leap_day.errors.full_messages # => [“Day is not valid for the month February”]

bad_month = 29, month: 0, year: 1999) bad_month.valid? # => false bad_month.errors.full_messages # => [“Month is not included in the list”] ```


activemodel-interdependence is released under the MIT license. See LICENSE for details.