State Validator for ActiveModel

README.rb

puts "State Validator"

class Purchase < ActiveRecord::Base
  belongs_to :order
  delegate :state_name, :to => :order, :prefix => true
  
  state_machine :state, :initial => :pending do
    state :pending
    state :confirmed do
      validates :order_state_name, :state => :paid
    end
  end
end

Gemfile

source 'http://rubygems.org'

gem 'activemodel', '>= 3.0.0', :require => 'active_model'
gem 'state_machine', '>= 1.0.0'
gem 'rspec', '~> 2.8.0'

Gemfile.lock

GEM
  remote: http://rubygems.org/
  specs:
    activemodel (3.2.2)
      activesupport (= 3.2.2)
      builder (~> 3.0.0)
    activesupport (3.2.2)
      i18n (~> 0.6)
      multi_json (~> 1.0)
    builder (3.0.0)
    diff-lcs (1.1.3)
    i18n (0.6.0)
    multi_json (1.1.0)
    rspec (2.8.0)
      rspec-core (~> 2.8.0)
      rspec-expectations (~> 2.8.0)
      rspec-mocks (~> 2.8.0)
    rspec-core (2.8.0)
    rspec-expectations (2.8.0)
      diff-lcs (~> 1.1.2)
    rspec-mocks (2.8.0)
    state_machine (1.1.2)

PLATFORMS
  ruby

DEPENDENCIES
  activemodel (>= 3.0.0)
  rspec (~> 2.8.0)
  state_machine (>= 1.0.0)

state_validator.gemspec

Gem::Specification.new do |s|
  s.name         = 'state_validator'
  s.summary      = 'Extending Rails validation to validate State Machines state'
  s.description  = 'Extending Rails validation to validate State Machines state'
  s.version      = '0.0.1'
  s.platform     = Gem::Platform::RUBY

  s.files        = ['state_validator.rb']
  s.require_path = '.'

  s.author      = 'Jan Bernacki'
  s.email       = '[email protected]'
  s.homepage    = 'http://gistflow.com'

  s.test_file    = 'state_validator_spec.rb'
  s.add_development_dependency('rspec', ["~> 2.8"])
  s.add_development_dependency('activemodel', ["~> 3.0.0"])
  s.add_development_dependency('state_machine', ["~> 1"])
end

state_validator.rb

module ActiveModel
  module Validations
    class StateValidator < EachValidator
      def validate_each(record, attribute, value)
        unless value.to_sym == options[:with].to_sym
          error = options[:message] || "#{value} is not #{options[:with]}"
          record.errors[attribute] << error
        end
      end
    end
  end
end

state_validator_spec.rb

require 'bundler/setup'
Bundler.require(:default)

require File.expand_path('state_validator')

class Base
  include ActiveModel::Validations
  attr_accessor :state
  
  state_machine :state, :initial => :active do
    state :active
    state :inactive
  end
end

class Foo < Base
  validates :state, :state => :active
end

class Bar < Base
  validates :state, :state => :inactive
end

describe 'Validations' do
  context 'valid record' do
    subject { Foo.new }
    it { should be_valid }
  end
  
  context 'invalid record' do
    subject { Bar.new }
    it { should be_invalid }
    it 'should add an error' do
      subject.valid?
      subject.errors[:state].size.should == 1
    end
  end
end