class Person
{
private:
    String _name;
    int _age = 0;

public:
    Person(String name)
        : Person{ name, 0 } // delegate initialization to Person(String, int) constructor
    {
    }

    Person(String name, int age)
        : _name{ name }, _age{ age } // actually initializes the members
    {
        Serial.print("Person ");Serial.print(_name); Serial.println(" created");
        Serial.print("age: ");Serial.println(_age); 
    }

};

void setup() {
  Serial.begin(115200);
  Person jack{"Jack"};
  Person john{"John",42};

}

void loop() {
}