define_state_query_method

# File activemodel/lib/active_model/state_machine.rb, line 35
      def define_state_query_method(state_name)
        name = "#{state_name}?"
        undef_method(name) if method_defined?(name)
        class_eval "def #{name}; current_state.to_s == %(#{state_name}) end"
      end