= Validation Scenarios

Define Validations on an ActiveRecord Model for special scenarios or exclude main Validations when in a scenario.

= Howto

Use validates_ methods in a Model in scenarios. The validation will only occur, if the
Model is used in a scenario:

  Model:
    class Event < ActiveRecord::Base
      validates_presence_of :title

      in_scenario :reviewer do |s|
         s.validates_presence_of :reviewer_note
      end

  Controller:
    class ReviewController < ApplicationController
      def create
        @event = Event.new(params[:event])
        @event.save!
      end

      def update
        with_scenario :reviewer do
          @event.save!
        end
      end

The :symbol given to #in_scenario is the identifier for the scenario, which is then activated
via the #with_scenario block.

If you want to exclude a default validation within a scenario, you may do so with the following
code:

  Model:
    class Event < ActiveRecord::Base
      validates_uniqueness_of :title, :unless => Proc.new { in_scenario? :bulk_insert }

      validates_presence_of :description, :unless => Proc.new { in_scenarios? :bulk_insert, :reviewer }

      in_scenario :reviewer do |s|
        s.validates_presence_of :reviewer_note
      end

You may have noticed the #in_scenarios? method, which can be used for multiple assignments of
scenarios.


Another use of scenarios in state machines will give you a clean implementation of scenario based
transitions. 
If in the above reviewer scenario only a state transition should be allowed as reviewer(using
the awesome state_machine plugin http://github.com/pluginaweek/state_machine), it is possible to 
express this like:

  Model:
     class Event < ActiveRecord::Base
       event :review do
         transition :open => :reviewed, :if => lambda { |event| event.in_scenario?(:reviewer) }
       end
       state :open
       state :reviewed
  
   Controller:
     class ReviewController < ApplicationController
  
       def update
         with_scenario :reviewer do
           @event.review!
         end
       end 

This is even more handy when the attribute update is more coupled to the current state of the model 
object.


More nifty stuff for the model (if you're not a block fan):

  Controller:
    class ReviewController < ApplicationController
      
      def update
        @event.save_in_scenario(:reviewer)
      end
      
      def create
        @event.save_in_scenario!(:admin)
      end

thx to theflow for this nice idea.

= Notes

This plugin reuses the name and some ideas of the http://code.google.com/p/validation-scenarios/ plugin, cause i was to lazy to find another name (just rubified it and asking for re-usage of the name).

= Rails Support

The tests are running with the following Rails versions:
* 2.3.2
* 2.3.1
* 2.2
* 2.1

= License

MIT-License, see MIT-LICENSE file


much fun with the plugin, love and peace for the world :D
any suggestions to: freetwix at web dot de

thx