new

# File activesupport/lib/active_support/notifications/fanout.rb, line 323
        def self.new(pattern, listener, monotonic)
          subscriber_class = monotonic ? MonotonicTimed : Timed

          if listener.respond_to?(:start) && listener.respond_to?(:finish)
            subscriber_class = Evented
          else
            # Doing this to detect a single argument block or callable
            # like `proc { |x| }` vs `proc { |*x| }`, `proc { |**x| }`,
            # or `proc { |x, **y| }`
            procish = listener.respond_to?(:parameters) ? listener : listener.method(:call)

            if procish.arity == 1 && procish.parameters.length == 1
              subscriber_class = EventObject
            end
          end

          subscriber_class.new(pattern, listener)
        end