motion/adapters/array_finder_query.rb
def new(options = {})
      raise ArgumentError.new("Creating on a relation requires the parent be saved first.") if @related_object.nil?

      id_field = (@related_object.class.to_s.underscore + '_id').to_sym
      new_obj = @klass.new(options.merge(id_field => @related_object.id))

      new_obj
    end
def new(options = {})
      raise ArgumentError.new("Creating on a relation requires the parent be saved first.") if @related_object.nil?

      id_field = (@related_object.class.to_s.underscore + '_id').to_sym
      new_obj = @klass.new(options.merge(id_field => @related_object.id))

      new_obj
    end
task.assignees.new(:name => 'BoB')
 creates a new unsaved Assignee object on the Task object task