Update MQTT component and add example

config/custom_components/mqtt_example.py

@@ -0,0 +1,60 @@
+"""
+custom_components.mqtt_example
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Shows how to communicate with MQTT. Follows a topic on MQTT and updates the
+state of an entity to the last message received on that topic.
+
+Also offers a service 'set_state' that will publish a message on the topic that
+will be passed via MQTT to our message received listener. Call the service with
+example payload {"new_state": "some new state"}.
+
+Configuration:
+
+To use the mqtt_example component you will need to add the following to your
+config/configuration.yaml
+
+mqtt_example:
+  topic: home-assistant/mqtt_example
+
+"""
+import homeassistant.loader as loader
+
+# The domain of your component. Should be equal to the name of your component
+DOMAIN = "mqtt_example"
+
+# List of component names (string) your component depends upon
+DEPENDENCIES = ['mqtt']
+
+
+CONF_TOPIC = 'topic'
+DEFAULT_TOPIC = 'home-assistant/mqtt_example'
+
+
+def setup(hass, config):
+    """ Setup our mqtt_example component. """
+    mqtt = loader.get_component('mqtt')
+    topic = config[DOMAIN].get('topic', DEFAULT_TOPIC)
+    entity_id = 'mqtt_example.last_message'
+
+    # Listen to a message on MQTT
+
+    def message_received(topic, payload, qos):
+        """ A new MQTT message has been received. """
+        hass.states.set(entity_id, payload)
+
+    mqtt.subscribe(hass, topic, message_received)
+
+    hass.states.set(entity_id, 'No messages')
+
+    # Service to publish a message on MQTT
+
+    def set_state_service(call):
+        """ Service to send a message. """
+        mqtt.publish(hass, topic, call.data.get('new_state'))
+
+    # Register our service with Home Assistant
+    hass.services.register(DOMAIN, 'set_state', set_state_service)
+
+    # return boolean to indicate that initialization was successful
+    return True