使用类的方法在typescript中创建联合类型

class Animal {
  name: string;
  constructor(name: string) {
    this.name = name;
  }
  move() {
    console.log(`${this.name} is moving.`);
  }
}

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

class Cat extends Animal {
  meow() {
    console.log(`${this.name} is meowing.`);
  }
}

let pet: Animal; // 声明一个变量，可以是Animal或其子类的实例

pet = new Animal("Animal");
pet.move(); // 输出 "Animal is moving."

pet = new Dog("Dog");
pet.move(); // 输出 "Dog is moving."
pet.bark(); // 输出 "Dog is barking."

pet = new Cat("Cat");
pet.move(); // 输出 "Cat is moving."
pet.meow(); // 输出 "Cat is meowing."