ep06_listing_10.rb

module Advertisements
 class Advertisement
   include AggregateRoot

   AlreadyPublished = Class.new(StandardError)
   NotPublished = Class.new(StandardError)
   NotAnAuthorOfAdvertisement = Class.new(StandardError)

   def initialize(id)
     @id = id
   end

   def publish(author_id)
     raise AlreadyPublished if @state.equal?(:published)
     apply AdvertisementPublished.new(data: {advertisement_id: @id, author_id: author_id})
   end

   def change_content(new_content, author_id)
     raise NotPublished unless @state.equal?(:published)
     raise NotAnAuthorOfAdvertisement unless @author_id.equal?(author_id)
     apply ContentHasChanged.new(data: {content: new_content})
   end

   on AdvertisementPublished do |event|
     @state = :published
     @author_id = event.data[:author_id]
   end

   on ContentHasChanged do |event|
   end
 end
end