/*
  https://forum.arduino.cc/t/init-funktion-bauen/1225735/3
*/

class Led {
    const uint8_t pin;
  public:
    Led(uint8_t pin) : pin(pin) {}
    
    void begin() {
      pinMode(pin, OUTPUT);
    }

    void on() {
      digitalWrite(pin, HIGH);
    }

    void off() {
      digitalWrite(pin, LOW);
    }
};

Led led[] {2, 4};              // create an array of object

const Led &ledGRUEN  = led[0]; // optional: create a meaningful reference to one instance so you don't need to remember what index is which LED...

void setup() {
  for (auto &i : led) {
    i.begin();
  }
}

void loop() {
  ledGRUEN.on();
  led[1].off();
  delay(500);
  ledGRUEN.off();
  led[1].on();
  delay(500);
}