transaction.rb

module Services
  class UserService
    #command is an "ActiveModel"
    def apply_command(user_id, command)
      aggregate = UserAggregate.find_or_create_by_id!(user_id)
      aggregate.with_lock do
        user = user_value(aggregate)
        event = command.apply(user)
        new_user = event.apply(user)
            
        aggregate.version += 1
        aggregate.events << Event.new(event_type: event.class.to_s, body: event.to_h, version: aggregate.version)
        aggregate.body = new_user.to_h
        aggregate.save!
      end 
    end 

    private

    def user_value(aggregate)
      user = Values::UserValue.new
      events = Event.where(aggregate_id: aggregate).order(:version)
      events.each do |e| 
        user = e.event_type.constantize.new(**e.body.symbolize_keys).apply(user) 
      end 
      user
    end 
  end 
end