// Forum: https://forum.arduino.cc/t/allocating-and-returning-an-array-of-structs-from-a-function/1261311/10
// Code by PieterP
// The ESP32 supports Serial.printf(), but then the variables
// have to match the %d, so I made them 'int'.

struct Person {
    char const* name;
    int age;
};

/*
template <class Callable>
void foreach_person(Callable callback) {
    static constexpr Person persons[] {
        {"John", 42},
        {"Jill", 43},
    };
    for (const Person &person : persons) {
        callback(person);
    }
}
*/

// A test to change the records.
template <class Callable>
void foreach_person(Callable callback) {
    Person persons[] = {
        {"John", 0},
        {"Jill", 0},
        {"Josh", 0},
        {"Jack", 0},
        {"Jasmin", 0},
    };
    int record = 0;
    for (Person &person : persons) {
        person.age = random(0,128);
        callback(record++,person);
    }
}

void setup() {
    Serial.begin(115200);
    Serial.println();

    int sum_of_ages = 0;
    foreach_person([&](int r, Person p) {
        Serial.printf("[%d] %s is %d years old\r\n", r, p.name, p.age);
        sum_of_ages += p.age;
    });
    Serial.printf("Their combined age is %d\r\n", sum_of_ages);
}

void loop() {
  delay(10);
}