# File lib/mongoid/document.rb, line 180 def becomes(klass) unless klass.include?(Mongoid::Document) raise ArgumentError, "A class which includes Mongoid::Document is expected" end klass.instantiate(frozen? ? attributes.dup : attributes).tap do |became| became.instance_variable_set(:@errors, errors) became.instance_variable_set(:@new_record, new_record?) became.instance_variable_set(:@destroyed, destroyed?) became._type = klass.to_s end end