stream_from

# File actioncable/lib/action_cable/channel/streams.rb, line 76
      def stream_from(broadcasting, callback = nil, coder: nil, &block)
        broadcasting = String(broadcasting)

        # Don't send the confirmation until pubsub#subscribe is successful
        defer_subscription_confirmation!

        # Build a stream handler by wrapping the user-provided callback with
        # a decoder or defaulting to a JSON-decoding retransmitter.
        handler = worker_pool_stream_handler(broadcasting, callback || block, coder: coder)
        streams[broadcasting] = handler

        connection.server.event_loop.post do
          pubsub.subscribe(broadcasting, handler, lambda do
            ensure_confirmation_sent
            logger.info "#{self.class.name} is streaming from #{broadcasting}"
          end)
        end
      end