Added lambda feature for onMessage callback

Author: rcarle3911

src/MQTTClient.cpp

@@ -101,8 +101,8 @@ static void MQTTClientHandler(lwmqtt_client_t * /*client*/, void *ref, lwmqtt_st
     return;
   }
 
-  // return if simple callback is not set
-  if (cb->simple == nullptr) {
+  // return if simple and lambda callbacks are not set
+  if (cb->simple == nullptr && cb->lambda == nullptr) {
     return;
   }
 
@@ -115,6 +115,12 @@ static void MQTTClientHandler(lwmqtt_client_t * /*client*/, void *ref, lwmqtt_st
     str_payload = String((const char *)message.payload);
   }
 
+  // call the lambda callback and return if available
+  if (cb->lambda != nullptr) {
+    cb->lambda(str_topic, str_payload);
+    return;
+  }
+
   // call simple callback
   cb->simple(str_topic, str_payload);
 }
@@ -163,17 +169,27 @@ void MQTTClient::begin(const char _hostname[], int _port, Client &_client) {
   lwmqtt_set_callback(&this->client, (void *)&this->callback, MQTTClientHandler);
 }
 
+void MQTTClient::onMessage(MQTTClientCallbackLambda cb) {
+  // set callback
+  this->callback.client = this;
+  this->callback.simple = nullptr;
+  this->callback.lambda = cb;
+  this->callback.advanced = nullptr;
+}
+
 void MQTTClient::onMessage(MQTTClientCallbackSimple cb) {
   // set callback
   this->callback.client = this;
   this->callback.simple = cb;
+  this->callback.lambda = nullptr;
   this->callback.advanced = nullptr;
 }
 
 void MQTTClient::onMessageAdvanced(MQTTClientCallbackAdvanced cb) {
   // set callback
   this->callback.client = this;
   this->callback.simple = nullptr;
+  this->callback.lambda = nullptr;
   this->callback.advanced = cb;
 }
 

src/MQTTClient.h

@@ -4,6 +4,7 @@
 #include <Arduino.h>
 #include <Client.h>
 #include <Stream.h>
+#include <functional>
 
 extern "C" {
 #include "lwmqtt/lwmqtt.h"
@@ -22,13 +23,15 @@ typedef struct {
 
 class MQTTClient;
 
+typedef std::function<void(String&, String&)> MQTTClientCallbackLambda;
 typedef void (*MQTTClientCallbackSimple)(String &topic, String &payload);
 typedef void (*MQTTClientCallbackAdvanced)(MQTTClient *client, char topic[], char bytes[], int length);
 
 typedef struct {
   MQTTClient *client = nullptr;
   MQTTClientCallbackSimple simple = nullptr;
   MQTTClientCallbackAdvanced advanced = nullptr;
+  MQTTClientCallbackLambda lambda = nullptr;
 } MQTTClientCallback;
 
 class MQTTClient {
@@ -66,6 +69,7 @@ class MQTTClient {
   void begin(const char _hostname[], Client &_client) { this->begin(_hostname, 1883, _client); }
   void begin(const char hostname[], int port, Client &client);
 
+  void onMessage(MQTTClientCallbackLambda cb);
   void onMessage(MQTTClientCallbackSimple cb);
   void onMessageAdvanced(MQTTClientCallbackAdvanced cb);