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TypeScript中extends与implements的区别

news 2025/11/12 5:34:46

在 TypeScript 中，extends 和 implements 都是用于实现面向对象编程中继承和多态的重要关键字

extends（继承）

extends 用于类之间的继承，一个类可以继承另一个类的属性和方法。

基本用法

class Animal {name: string;constructor(name: string) {this.name = name;}move(distance: number = 0) {console.log(`${this.name} moved ${distance}m.`);}
}class Dog extends Animal {breed: string;constructor(name: string, breed: string) {super(name); // 必须调用父类的构造函数this.breed = breed;}bark() {console.log("Woof! Woof!");}// 重写父类方法move(distance: number = 5) {console.log("Running...");super.move(distance); // 调用父类方法}
}const dog = new Dog("Buddy", "Golden Retriever");
dog.move(10); // Running... Buddy moved 10m.
dog.bark();   // Woof! Woof!

继承的原理

原型链继承：子类的原型对象指向父类的实例
构造函数调用：必须调用 super() 来初始化父类
方法重写：子类可以重写父类方法，通过 super 调用父类实现

implements（实现接口）

implements 用于类实现接口，确保类满足接口定义的契约。

基本用法

interface Animal {name: string;move(distance: number): void;
}interface Pet {owner: string;play(): void;
}class Dog implements Animal, Pet {name: string;owner: string;breed: string;constructor(name: string, owner: string, breed: string) {this.name = name;this.owner = owner;this.breed = breed;}move(distance: number) {console.log(`${this.name} ran ${distance} meters`);}play() {console.log(`${this.name} is playing with ${this.owner}`);}bark() {console.log("Woof!");}
}

实现多个接口

interface Swimmer {swim(): void;
}interface Flyer {fly(): void;
}class Duck implements Swimmer, Flyer {swim() {console.log("Duck is swimming");}fly() {console.log("Duck is flying");}
}

主要区别

特性	extends	implements
用途	类继承类	类实现接口
继承实现	继承具体实现	只继承类型约束
多重继承	不支持（单继承）	支持（多接口实现）
构造函数	必须调用 `super()`	不需要调用 `super()`
方法实现	自动继承父类实现	必须自己实现所有方法

高级用法

接口继承接口

interface Animal {name: string;
}interface Mammal extends Animal {hasFur: boolean;
}interface Pet extends Mammal {owner: string;
}class Cat implements Pet {name: string;hasFur: boolean = true;owner: string;constructor(name: string, owner: string) {this.name = name;this.owner = owner;}
}

类实现泛型接口

interface Repository<T> {findById(id: number): T | undefined;save(entity: T): void;
}class UserRepository implements Repository<User> {private users: User[] = [];findById(id: number): User | undefined {return this.users.find(user => user.id === id);}save(user: User): void {this.users.push(user);}
}

混合使用 extends 和 implements

class Vehicle {start() {console.log("Vehicle started");}
}interface Electric {batteryLevel: number;charge(): void;
}class ElectricCar extends Vehicle implements Electric {batteryLevel: number = 100;charge() {this.batteryLevel = 100;console.log("Fully charged");}// 继承自 Vehicle// start() 方法已存在
}