Nodemanager: How to control a local output from a local input?

[A3V]

I am trying to make a temperature control system that has a temperature sensor and a relay.
I use an ESP32 and set it op as gateway. The sensor and relay are connected to the ESP32
The sensor and relay should form a closed loop and should be able to run independently from the (Domoticz) controller.
I want to use the Nodemanager to be able to track the temperature and relay state.
In my first test I can read my sensor and I can switch my relay from Domoticz.
I tried to add some code to the loop() to read the temperature locally and print it to the serial port:
When I e.g. try to print Tsensor.getChild(0)->getValueString() it throws an error.
My question: what is the proper way to do this?
How can I get the sensor value and set the relay?
Any suggestions are much appreciated

[A3V]

Reply to myself:
Looking thought the sources and the forum found out that you can do this using hooks.
so enabled hooking

#define NODEMANAGER_HOOKING ON

and added the reference to the hook to before.

void before() {
 Tsensor.setMeasureTimerMode(TIME_INTERVAL);   // set timer 
 Tsensor.setMeasureTimerValue(1); // interval to 1 sec measurement

 Tsensor.setPostLoopHook(&myfirstHook);
 ..etc.etc...
 nodemanager.before();
}

And finally the hook

void myfirstHook(Sensor* sensor){
  float temperature =  Tsensor.children.get(1)->getValueFloat()
  Serial.println(temperature);
  if (temperature>setpoint) { 
        if (Relay.getStatus()==OFF){
        Relay.setStatus(ON);      // switch off
        } 
  

}

The error that I got initially was caused by using the wrong child: 0 (it starts from 1).

I wonder if it is possible to do interval < 1 second?