explains about abstract classes,interfaces, mixins and castings in dart

classes-2.dart

import 'dart:math';

void main() {
  A c = C("tokyo");
  c.hello();
  (c as B).goodBye();
  (c as C).hi();
  (c as C).printStamp();
}

class TimeStamp {
  DateTime time = DateTime.now();
  void printStamp() {
    print(time);
  }
}

/// mixins has to follow certain conditions
// 1) the class must have no declared constructors
// 2) the class must not be a subclass of anything other than String() [cannot use the extends keyword ]
// 3) it must have a no calls to the super keyword, [in other words it must not inherit anything]

// void main() {
// //   Square square = Square(23.0);
// //   Rectangle rectangle = Rectangle(12.0, 30.0);
// //   Circle circle = Circle(15.0);

// //   print(square.name);
// //   print(rectangle.name);
// //   print(circle.name);

//   Shape randShape;

//   Random random = Random();
//   int choice = random.nextInt(3);

//   switch (choice) {
//     case 0:
//       randShape = Circle(
//         random.nextInt(10) + 1.0,
//       );
//       break;
//     case 1:
//       randShape = Rectangle(
//         random.nextInt(10) + 1.0,
//         random.nextInt(10) + 1.0,
//       );
//       break;
//     case 2:
//       randShape = Square(
//         random.nextInt(10) + 1.0,
//       );
//       break;
//     default:
//       print("will never exceute");
//   }

//   print(randShape.name);
//   print(randShape.area);
//   print(randShape.perimeter);
// }

class A {
  void hello() {
    print("hello from A");
  }
}

class B {
  String b;

  B(this.b);
  void hi() {
    print("hi from B");
  }

  void goodBye() {
    print("bye bye $b");
  }
}

class C with TimeStamp implements A, B {
  C(this.b);

  @override
  void hello() {
    print("hello from C");
  }

  @override
  void hi() {
    print("hi from C");
  }

  @override
  String b;

  @override
  void goodBye() {
    print("this is overrided print from $b");
  }
}

abstract class Shape {
  double get perimeter;
  double get area;
  String get name;
}

class Circle extends Shape {
  double radius;

  Circle(this.radius);

  @override
  double get area => pi * (radius * radius);

  @override
  double get perimeter => 2 * pi * radius;

  @override
  String get name => "I'm a circle with a radius $radius";
}

class Rectangle extends Shape {
  double length, width;

  Rectangle(this.length, this.width);

  @override
  double get area => length * width;

  @override
  double get perimeter => 2 * (length + width);

  @override
  String get name =>
      "I'm a reactangle with a length: $length and a height: $width";
}

class Square extends Rectangle {
  Square(double side) : super(side, side);

  @override
  String get name => "I'm a Square with a side of $length";
}