gistfile1.rb

include AASM
include AASM::Persistence
aasm_column :status

aasm_initial_state Proc.new { |task| task.assignments.empty? ? :not_started }
aasm_state :not_started
aasm_state :in_progress
aasm_state :completed

aasm_event :start_task do
  transitions :to => :in_progress, :from => :not_started
end

aasm_event :complete_task do
  transitions :to => :completed, :from => :in_progress
end