This code is unable to verify

Official Hardware Nano Family Nano ESP32
1 
type or paste code#include "thingProperties.h"
#include <Servo.h>
Servo myservo;
int pos = 0;
String password = "Eduvate@123";
String msg1 = "Please Enter the password";
String msg2 = "Please Enter the password again";
void setup() {
  myservo.attach(15);
  status = false;
  myservo.write(0);
  messenger = msg1;
  Serial.begin(9600);
  delay(1500);
  initProperties();
  ArduinoCloud.begin(ArduinoIoTPreferredConnection);
  setDebugMessageLevel(2);
  ArduinoCloud.printDebugInfo();
}
void loop() {
  ArduinoCloud.update();
  if (messenger == password) {
    status = true;
    myservo.write(90);
  }
  else {
    messenger = msg2;
    status = false;
    myservo.write(0);
  }
} here

these are the codes and error showing is
/usr/local/bin/arduino-cli compile --fqbn esp32:esp32:esp32doit-devkit1:DebugLevel=none,EraseFlash=none,FlashFreq=80,UploadSpeed=921600 --build-cache-path /tmp --output-dir /tmp/1905636055/build --build-path /tmp/arduino-build-5B15740DBB43943E43497556A5939BF8 /tmp/1905636055/Smart_Lock_apr13a

/home/builder/.arduino15/packages/esp32/tools/xtensa-esp32-elf-gcc/gcc8_4_0-esp-2021r2-patch3/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld: /tmp/arduino-build-5B15740DBB43943E43497556A5939BF8/sketch/objs.a(Smart_Lock_apr13a.ino.cpp.o):(.literal._Z14initPropertiesv+0x18): undefined reference to `onMessengerChange()'

collect2: error: ld returned 1 exit status

Multiple libraries were found for "WiFiClientSecure.h"

Used: /home/builder/.arduino15/packages/esp32/hardware/esp32/2.0.5/libraries/WiFiClientSecure

Not used: /home/builder/opt/libraries/seeed_arduino_rpcwifi_1_0_7

Multiple libraries were found for "WiFi.h"

Used: /home/builder/.arduino15/packages/esp32/hardware/esp32/2.0.5/libraries/WiFi

Not used: /home/builder/opt/libraries/seeed_arduino_rpcwifi_1_0_7

Not used: /home/builder/opt/libraries/wifiespat_1_4_3

Not used: /home/builder/opt/libraries/nina_wi_fi_1_0_1

Not used: /home/builder/opt/libraries/indhilib_3_0_5

Not used: /home/builder/opt/libraries/wifinina_1_8_14

Not used: /home/builder/opt/libraries/da16200_wi_fi_library_for_arduino_1_1_0

Not used: /home/builder/opt/libraries/vega_wifinina_1_0_1

Not used: /home/builder/opt/libraries/wifi_1_2_7

Multiple libraries were found for "Servo.h"

Used: /home/builder/opt/libraries/servoesp32fix_1_1_2

Not used: /home/builder/opt/libraries/evive_2_0_3

Not used: /home/builder/opt/libraries/servo_1_2_1

Not used: /home/builder/opt/libraries/servoesp32_1_1_1

Not used: /home/builder/opt/libraries/vovagorodok_servo_1_0_0

Not used: /home/builder/opt/libraries/rokitsmart_1_0_9

Not used: /home/builder/opt/libraries/printoo_library_1_0_2

Not used: /home/builder/opt/libraries/esp32_esp32s2_analogwrite_5_0_2

Not used: /home/builder/opt/libraries/xmc_servo_1_0_1

Not used: /home/builder/opt/libraries/microbitv2_hhs_0_1_6

Error during build: exit status 1

2

Hi @harshwakle123456789. When you configure the permissions of an Arduino Cloud Variable as "read & write", the generated Thing sketch code is written to call a function whenever the value of the Variable is changed via the Arduino Cloud dashboard.

The cause of this error is that you removed this "callback" function for the messenger Variable from the sketch code.

You can fix it by adding the missing function definition to your sketch:

void onMessengerChange()  {
  // Add your code here to act upon messenger change
}

If you don't have any use for this "callback" feature in your sketch, you can simply leave the function empty.

If you don't plan to change the value of the messenger Variable from the Arduino Cloud dashboard, then you can change the Variable permissions in the Thing configuration from "read & write" to "Read only".