2-10-dart_classes.dart

// 1.
class User {
  User(this.name, this.surname);

  String name;
  String surname;

  @override
  String toString() {
    return 'User(name: $name, surname: $surname)';
  }
}

class Student extends User {
  Student(String name, String surname, this.yearOfAdmission)
      : super(name, surname);

  DateTime yearOfAdmission;
  int get currentCourse {
    return DateTime.now().year - yearOfAdmission.year;
  }

  @override
  String toString() {
    return '${super.toString()} / '
        'Student(yearOfAdmission: $yearOfAdmission, currentCourse: $currentCourse)';
  }
}

// 2.
abstract class Car with Painter {
  Car(Colors color) {
    setColor(color);
  }

  double get weight;
  void run();

  @override
  String toString() {
    return 'colorName: $colorName';
  }
}

class Truck extends Car with Engine {
  Truck(Colors color, int engine) : super(color) {
    enginePower = engine;
  }

  @override
  double get weight => 2;

  @override
  void run() {
    runEngine();
  }

  @override
  String toString() {
    return 'Грузовик $colorName цвета';
  }
}

class Sportcar extends Car with Engine {
  Sportcar(Colors color, int engine) : super(color) {
    enginePower = engine;
  }

  @override
  double get weight => 2;

  @override
  void run() {
    runEngine();
  }

  @override
  String toString() {
    return 'Гоночная машина $colorName цвета';
  }
}

class Bike with Painter {}

enum Colors { red, green, blue }

mixin Painter {
  late String colorName;
  void setColor(Colors color) => colorName = color.name;
}

mixin Engine on Car {
  int enginePower = 200;
  void runEngine() {
    print(
        'Двигатель работает. Максимальная скорость = ${enginePower ~/ weight}');
  }
}

// 3.
class Stringer<T> {
  String toStr(T value) {
    return value.toString();
  }
}

void main() {
  // 1.
  DateTime yearOfAdmission = DateTime(2019);
  final student = Student('Pavel', 'Bakun', yearOfAdmission);
  print(student);

  // 2.
  final truck = Truck(Colors.green, 170);
  print(truck);
  truck.run();

  final sportCar = Sportcar(Colors.red, 400);
  print(sportCar);
  sportCar.run();

  // 3.
  final stringer = Stringer();
  print(stringer.toStr(123));
  print(stringer.toStr(123.0));
}