Simple example of a checklist using ruby state_machine gem

list_example.rb

require 'rubygems'
require 'state_machine'

class Item    

    attr_accessor :name, :description 
    
    state_machine :item_state, :initial => :available do  
        
        after_transition :available=> :completed, :do => :item_completed

        event :finish do
            transition [:available] => :completed
        end 

        state :completed do 
        end
        
      end

      def initialize(item_name, item_description, parent = nil)
          @name = item_name 
          @description = item_description  
          @parent_list = parent

          super() # NOTE: This *must* be called, otherwise states won't get initialized
      end  
      
      def item_completed
        puts "finished item #{self.name}"
        if @parent_list
            @parent_list.child_item_completed 
        end
      end
      
end
 
class List    
    attr_accessor :name, :description, :lists, :items 
    
    state_machine :list_state, :initial => :available do  

        after_transition :started=> :completed, :do => :list_completed
                   
        event :start do
              transition [:available] => :started
        end

        event :finish do
              transition [:started] => :completed
        end 

        state :started do 
            # take any actions related to moving to started state.
        end 

        state :completed do 
            # take any actions related to moving to completed state.
        end

      end

      def initialize(list_name, list_description, parent = nil)  
          @name = list_name 
          @description = list_description 
          @lists = [] 
          @items = []
          @parent = parent

          super() # NOTE: This *must* be called, otherwise states won't get initialized
      end  
      
      def add_list(name, description) 
             @lists << List.new(name, description, self)
             @lists.last
      end

      def add_item (name, description)
             @items << Item.new(name, description, self)
             @items.last
      end
      
      # Called by child item when item is completed. Allows check for 
      # all items completed. 
      def child_item_completed
          # once the first item is completed consider this list started
          if self.list_state == "available"
             self.fire_events(:start)
          end
           
          # if all items are completed move this list to completed state. 
          if self.items.select{|i| i.item_state != "completed"}.empty?
             self.fire_events(:finish) 
          end           
      end

      
      def child_list_completed
            # if this is a sublist let parent know this list is completed.
            # else this is top level list and everything is completed.
            if self.items.select{|i| i.item_state != "completed"}.empty?
                if self.lists.select{|l| l.list_state != "completed"}.empty?
                     self.fire_events(:finish) 
                end
            end
      end
      
      def list_completed 
          if @parent 
              puts "congrats on completing list #{self.name}"  
              @parent.child_list_completed 
          else 
             puts "congrats on completing project #{self.name}" 
          end
      end
      
 end