TypeScript：类

一、基本概念

TypeScript 类是基于 ES6 类的语法扩展，增加了类型注解和访问修饰符等特性，提供了更强大的面向对象编程能力。

二、基本语法

class Person {name: string;age: number;constructor(name: string, age: number) {this.name = name;this.age = age;}greet() {return `Hello, my name is ${this.name}`;}
}

三、类的主要特性

1. 访问修饰符

public (默认)：成员在任何地方都可访问
private：只能在类内部访问
protected：可在类及其子类中访问

class Animal {public name: string;private secret: string;protected age: number;
}

2. 只读属性

class Person {readonly birthDate: Date;
}

3. 参数属性

简化属性声明和赋值的语法：

class Person {constructor(public name: string, private age: number) {}// 等同于声明name和age并在构造函数中赋值
}

4. 存取器 (getters/setters)

class Employee {private _salary: number;get salary(): number {return this._salary;}set salary(newSalary: number) {if (newSalary >= 0) {this._salary = newSalary;}}
}

5. 静态成员

class Grid {static origin = { x: 0, y: 0 };static calculateDistance(point: {x: number, y: number}) {// ...}
}

6. 抽象类

abstract class Animal {abstract makeSound(): void; // 必须在派生类中实现move(): void {console.log("moving...");}
}

7. 类与接口

类可以实现接口：

interface ClockInterface {currentTime: Date;setTime(d: Date): void;
}class Clock implements ClockInterface {currentTime: Date = new Date();setTime(d: Date) {this.currentTime = d;}
}

四、继承

class Animal {move(distance: number = 0) {console.log(`Moved ${distance}m`);}
}class Dog extends Animal {bark() {console.log("Woof! Woof!");}
}

五、方法重写

class Animal {move(distance: number = 0) {console.log(`Moved ${distance}m`);}
}class Snake extends Animal {move(distance: number = 5) {console.log("Slithering...");super.move(distance);}
}

六、高级特性

1. 类类型

类既可以作为值使用，也可以作为类型使用：

class Greeter {greeting: string;constructor(message: string) {this.greeting = message;}
}let greeter: Greeter = new Greeter("world");

2. 构造函数类型

class Point {x: number;y: number;
}let PointConstructor: typeof Point = Point;
let point: Point = new PointConstructor();

3. 装饰器 (实验性特性)

@sealed
class Greeter {greeting: string;constructor(message: string) {this.greeting = message;}@enumerable(false)greet() {return "Hello, " + this.greeting;}
}