nohum#9 fix exception when finding chromecast devices before being co…

…nnected to mqtt

(cherry picked from commit 4534f20)

handler/event.py

@@ -51,9 +51,13 @@ def __init__(self):
         self.processing_worker.daemon = True
         self.processing_worker.start()
 
-    def on_mqtt_connected(self, client):
-        self.logger.debug("mqtt connected callback has been invoked")
+    def on_mqtt_init_done(self, client):
+        self.logger.debug("mqtt object is available")
         self.mqtt_client = client
+
+    def on_mqtt_connected(self):
+        self.logger.debug("mqtt connected callback has been invoked")
+
         # insert + as identifier so that every command to every identifier (= friendly names) will be recognized
         self.mqtt_client.subscribe(TOPIC_COMMAND_VOLUME_LEVEL % "+")
         self.mqtt_client.subscribe(TOPIC_COMMAND_VOLUME_MUTED % "+")

helper/mqtt.py

@@ -4,7 +4,13 @@
 
 class MqttConnectionCallback:
 
-    def on_mqtt_connected(self, client):
+    def on_mqtt_init_done(self, client):
+        """
+        Called if there is a mqtt connection class available (but not necessarily connected yet)
+        """
+        pass
+
+    def on_mqtt_connected(self):
         pass
 
     def on_mqtt_message_received(self, topic, payload):
@@ -33,6 +39,8 @@ def __init__(self, ip, port, username, password, cafile, connection_callback):
         self.connection_callback = connection_callback
         self.queue = []
 
+        self.connection_callback.on_mqtt_init_done(self)
+
     def _on_connect(self, client, userdata, flags, rc):
         """
         The callback for when the client receives a CONNACK response from the server.
@@ -42,7 +50,7 @@ def _on_connect(self, client, userdata, flags, rc):
 
         # subscribing in on_connect() means that if we lose the connection and
         # reconnect then subscriptions will be renewed.
-        self.connection_callback.on_mqtt_connected(self)
+        self.connection_callback.on_mqtt_connected()
 
         if len(self.queue) > 0:
             self.logger.debug("found %d queued messages" % len(self.queue))