instantiate_observer

# File activemodel/lib/active_model/observing.rb, line 63
        def instantiate_observer(observer) #:nodoc:
          # string/symbol
          if observer.respond_to?(:to_sym)
            observer = observer.to_s.camelize.constantize.instance
          elsif observer.respond_to?(:instance)
            observer.instance
          else
            raise ArgumentError, "#{observer} must be a lowercase, underscored class name (or an instance of the class itself) responding to the instance method. Example: Person.observers = :big_brother # calls BigBrother.instance"
          end
        end