Add method ActionCable::Channel#stream_or_reject_for to stream if record is present, otherwise reject the connection

actioncable/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Add `ActionCable::Channel#stream_or_reject_for` to stream if record is present, otherwise reject the connection
+
+    *Atul Bhosale*
+
 *   Add `ActionCable::Channel#stop_stream_from` and `#stop_stream_for` to unsubscribe from a specific stream.
 
     *Zhang Kang*

actioncable/lib/action_cable/channel/streams.rb

@@ -124,6 +124,18 @@ def stop_all_streams
         end.clear
       end
 
+      # Calls stream_for if record is present, otherwise calls reject.
+      # This method is intended to be called when you're looking
+      # for a record based on a parameter, if its found it will start
+      # streaming. If the record is nil then it will reject the connection.
+      def stream_or_reject_for(record)
+        if record
+          stream_for record
+        else
+          reject
+        end
+      end
+
       private
         delegate :pubsub, to: :connection
 

actioncable/test/channel/stream_test.rb

@@ -110,6 +110,39 @@ class StreamTest < ActionCable::TestCase
       end
     end
 
+    test "stream_or_reject_for" do
+      run_in_eventmachine do
+        connection = TestConnection.new
+
+        channel = ChatChannel.new connection, ""
+        channel.subscribe_to_channel
+        channel.stream_or_reject_for Room.new(1)
+        wait_for_async
+
+        pubsub_call = channel.pubsub.class.class_variable_get "@@subscribe_called"
+
+        assert_equal "action_cable:stream_tests:chat:Room#1-Campfire", pubsub_call[:channel]
+        assert_instance_of Proc, pubsub_call[:callback]
+        assert_instance_of Proc, pubsub_call[:success_callback]
+      end
+    end
+
+    test "reject subscription when nil is passed to stream_or_reject_for" do
+      run_in_eventmachine do
+        connection = TestConnection.new
+        channel = ChatChannel.new connection, "{id: 1}", id: 1
+        channel.subscribe_to_channel
+        channel.stream_or_reject_for nil
+        assert_nil connection.last_transmission
+
+        wait_for_async
+
+        rejection = { "identifier" => "{id: 1}", "type" => "reject_subscription" }
+        connection.transmit(rejection)
+        assert_equal rejection, connection.last_transmission
+      end
+    end
+
     test "stream_from subscription confirmation" do
       run_in_eventmachine do
         connection = TestConnection.new