From 8e711605167aff6b09c1ca8e3e6b1cdaed207ea1 Mon Sep 17 00:00:00 2001
From: Ronald Schaten <ronald@schatenseite.de>
Date: Wed, 24 Feb 2016 08:43:44 +0100
Subject: [PATCH] dynamic creation of MQTT topic

---
 things.ino | 41 ++++++++++++++++-------------------------
 1 file changed, 16 insertions(+), 25 deletions(-)

diff --git a/things.ino b/things.ino
index 3963d30..c37bd37 100644
--- a/things.ino
+++ b/things.ino
@@ -70,6 +70,14 @@ bool isEqual(float a, float b, float epsilon=0.001) {
   return fabs(a - b) <= epsilon * fabs(a);
 }
 
+char* topic(const char* this_topic) {
+  static char topic[34];
+  strcpy(topic, mqtt_topic);
+  strcat(topic, "/");
+  strcat(topic, this_topic);
+  return topic;
+}
+
 void read_sensor() {
   // wait at least 2 seconds seconds between measurements
   unsigned long currentMillis = millis();
@@ -96,21 +104,14 @@ void read_sensor() {
     dtostrf(temperature, 1, 2, str_temperature);
     dtostrf(heatindex, 1, 2, str_heatindex);
 
-    char pub_topic[34];
     if (!isEqual(humidity, previousHumidity)) {
-      strcpy(pub_topic,mqtt_topic);
-      strcat(pub_topic,"/humidity");
-      client.publish(pub_topic, str_humidity);
+      client.publish(topic("humidity"), str_humidity);
     }
     if (!isEqual(temperature, previousTemperature)) {
-      strcpy(pub_topic,mqtt_topic);
-      strcat(pub_topic,"/temperature");
-      client.publish(pub_topic, str_temperature);
+      client.publish(topic("temperature"), str_temperature);
     }
     if (!isEqual(heatindex, previousHeatindex)) {
-      strcpy(pub_topic,mqtt_topic);
-      strcat(pub_topic,"/heatindex");
-      client.publish(pub_topic, str_heatindex);
+      client.publish(topic("heatindex"), str_heatindex);
     }
 
     Serial.print("Humidity: ");
@@ -151,13 +152,10 @@ void reconnect() {
   while (!client.connected()) {
     Serial.print("Attempting MQTT connection...");
     // Attempt to connect
-    char pub_topic[34];
-    strcpy(pub_topic,mqtt_topic);
-    strcat(pub_topic,"/online");
-    if (client.connect(wifi_station_get_hostname(), pub_topic, MQTTQOS1, true, "0")) {
+    if (client.connect(wifi_station_get_hostname(), topic("online"), MQTTQOS1, true, "0")) {
       Serial.println("connected");
       // Once connected, publish an announcement...
-      client.publish(pub_topic, "1");
+      client.publish(topic("online"), "1");
       // ... and resubscribe:
       client.subscribe("inTopic");
     } else {
@@ -300,16 +298,9 @@ void setup() {
 
   // Initial read
   read_sensor();
-  char pub_topic[34];
-  strcpy(pub_topic,mqtt_topic);
-  strcat(pub_topic,"/humidity");
-  client.publish(pub_topic, str_humidity);
-  strcpy(pub_topic,mqtt_topic);
-  strcat(pub_topic,"/temperature");
-  client.publish(pub_topic, str_temperature);
-  strcpy(pub_topic,mqtt_topic);
-  strcat(pub_topic,"/heatindex");
-  client.publish(pub_topic, str_heatindex);
+  client.publish(topic("humidity"), str_humidity);
+  client.publish(topic("temperature"), str_temperature);
+  client.publish(topic("heatindex"), str_heatindex);
 
   // Handle http requests
   server.on("/", [](){