Simplifying code, getting invalid conversion from 'const char*' to 'char*'

Question

I have a program that does 4 times the same thing with different parapmeters; and was trying to simplify my code to take one parameter as a variable.

Example (what was):

const char MQTT_PUB_IRRIGATION_TANK_VALVE[]      = "ArgyleCourt/Property/Hub/IrrigationTank/Valve";
const char MQTT_PUB_HOUSE_BOREWATER_TANK_VALVE[] = "ArgyleCourt/Property/Hub/HouseBoreWaterTank/Valve";

publishTankValveStatusIrrigation(false);

void publishTankValveStatusIrrigation(bool demandStatus) {
  if (demandStatus) {
    mqttClient.publish(MQTT_PUB_IRRIGATION_TANK_VALVE, "ON");
  } else {
    mqttClient.publish(MQTT_PUB_IRRIGATION_TANK_VALVE, "OFF");
  }
}

publishTankValveStatusHouse(false);

void publishTankValveStatusHouse(bool demandStatus) {
  if (demandStatus) {
    mqttClient.publish(MQTT_PUB_HOUSE_BOREWATER_TANK_VALVE, "ON");
  } else {
    mqttClient.publish(MQTT_PUB_HOUSE_BOREWATER_TANK_VALVE, "OFF");
  }
}

to one function now passing the topic also inot the function, thus needing only one function:

publishTankValveStatus(false, MQTT_PUB_IRRIGATION_TANK_VALVE);
publishTankValveStatus(false, MQTT_PUB_HOUSE_BOREWATER_TANK_VALVE);

void publishTankValveStatus(bool demandStatus, char topicToPublishTo) {
  if (demandStatus) {
    mqttClient.publish(topicToPublishTo, "ON");
  } else {
    mqttClient.publish(topicToPublishTo, "OFF");
  }
}

when I compile the simplified function, I get "warning: invalid conversion from 'const char*' to 'char' [-fpermissive]", but do neither understand why or how to fix it.

Answer 1

The function declaration

void publishTankValveStatus(bool demandStatus, char topicToPublishTo)

declares topicToPublishTo as a char, that is, as a single character instead of as an array of characters that is constant.

Change char to const char * to say that topicToPublishTo is an array of characters that is constant.