类

类的使用

1. 实例一

// 构造函数
class Person1 {
  age: number;
  gender: string;
  constructor(age: number, gender: string) {
    // 构造函数没有返回值类型
    this.age = age;
    this.gender = gender;
  }
}
const p1 = new Person1(19, "女");
console.log(p1.age, p1.gender);

// 实例方法
class Point {
  x = 2;
  y = 3;
  scale(n: number) {
    this.x *= n;
    this.y *= n;
  }
}
const p2 = new Point();
p2.scale(10);
console.log(p2.x, p2.y);

// 类的继承 方法1
class Animal {
  move() {
    console.log("Animal move");
  }
}
class Dog extends Animal {
  bark() {
    console.log("Dog wang");
  }
}
const d = new Dog();
d.move();
d.bark();

// 类的继承 方法2
interface Singable {
  sing(song: string): void;
}
class SingPerson implements Singable {
  sing(song: string) {
    console.log(song);
  }
}
const p = new SingPerson();
p.sing("你是我的小苹果");

2. 实例二

class Animal {
  name: string;
  static categoies: string[] = ["mammal", "bird"];
  static isAnimal(a) {
    return a instanceof Animal;
  }
  constructor(name: string) {
    this.name = name;
  }
  run() {
    return `${this.name} is running`;
  }
}

console.log(Animal.categoies);
const snake = new Animal("lily");
console.log(Animal.isAnimal(snake));

class Dog extends Animal {
  bark() {
    return `${this.name} is barking`;
  }
}

const xiaobao = new Dog("xiaobao");

class Cat extends Animal {
  constructor(name) {
    super(name);
    console.log(this.name);
  }
  run() {
    return "Meow, " + super.run();
  }
}

const maomao = new Cat("maomao");

interface Radio {
  switchRadio(): void;
}

interface Battery {
  checkBatteryStatus();
}
interface RadioWithBattery extends Radio {
  checkBatteryStatus();
}
class Car implements Radio {
  switchRadio() {}
}

class Cellphone implements RadioWithBattery {
  switchRadio() {}
  checkBatteryStatus() {}
}

3. 类兼容性

class Point {
  x: number;
  y: number;
}

class Point2D {
  x: number;
  y: number;
}

const p: Point = new Point2D();

class Point3D {
  x: number;
  y: number;
  z: number;
}

const p1: Point = new Point3D();

4. 接口兼容性

interface Point {
  x: number;
  y: number;
}
interface Point2D {
  x: number;
  y: number;
}
interface Point3D {
  x: number;
  y: number;
  z: number;
}

let p1: Point;
let p2: Point2D;
let p3: Point3D;

// 正确：
// p1 = p2
// p2 = p1
// p1 = p3

// 错误演示：
// p3 = p1

// 类和接口之间也是兼容的
class Point4D {
  x: number;
  y: number;
  z: number;
}
p2 = new Point4D();