Use change listener rather than direct message factory for lidar.

tracking/lidar_cache.py

@@ -2,7 +2,6 @@ from threading import Thread
 from tracking import algorithms
 import tracking.lidar_tracker_pb2 as tracker_pb
 import zmq
-import messaging.messages as messages
 
 
 class LidarCache():
@@ -25,17 +24,17 @@ class LidarCache():
         self.thread = Thread(target=self.do_scanning, args=[sender])
         self.thread.start()
 
-    def do_scanning(self, sender):
+    def do_scanning(self, listener):
         """Performs scans whilst cache is running, and will pass calculated groups data to the sender.
 
         Parameters
         ----------
-        sender: 
-            Any class given in messaging.message_factory. This acts as a listener.
+        listener: 
+            Any object that includes the onGroupsChanged method. 
 
         """
         # Create the 0MQ socket first. This should not be passed between threads.
-        self._mFactory = sender
+        self._mFactory = listener
 
         # Batch over scans, so we don't need to do our own batching to determine groups
         # TODO: Implement custom batching, as iter_scans can be unreliable
@@ -66,8 +65,7 @@ class LidarCache():
                 pointScan.points.append(tracker_pb.Point(
                     angle=point[1], distance=point[2], group_number=group.number))
 
-        self._mFactory.send_message_topic(
-            "lidar_map", messages.ProtoMessage(message=pointScan.SerializeToString()))
+        self._mFactory.onGroupsChanged(pointScan)
 
     def stop_scanning(self):
         self.run = False

tracking/lidar_servicer.py

@@ -4,12 +4,16 @@ from tracking.lidar_cache import LidarCache
 from multiprocessing import Process
 import messaging.message_factory as mf
 from rplidar import RPLidar
+from Messaging import messages
+
 
 class LidarServicer(PersonTrackingServicer):
 
     def __init__(self):
-        #TODO: Put the rplidar creation in a factory or something, to make it possible to test this servicer.
+        # TODO: Put the rplidar creation in a factory or something, to make it possible to test this servicer.
         self.cache = LidarCache(RPLidar('/dev/ttyUSB0'), measurements=100)
+        self._mFactory = None
+        self._port = None
 
     def set_tracking_group(self, request, context):
         pass
@@ -19,4 +23,11 @@ class LidarServicer(PersonTrackingServicer):
 
     def start_tracking(self, request, context):
         """Starts the lidar cache, streaming on the provided port."""
-        self.cache.start_cache(mf.getZmqPubSubStreamer(request.value))
+        self._port = request.value
+        self.cache.start_cache(self)
+
+    def onGroupsChanged(self, message):
+        if self._mFactory is None:
+            # Create the zmq socket in the thread that it will be used, just to be safe.
+            self._mFactory = mf.getZmqPubSubStreamer(self._port)
+        self._mFactory.send_message_topic("lidar_map", messages.ProtoMessage(message=message.SerializeToString()))