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类
class Greeter { greeting: string; constructor (message: string) { this.greeting = message; } greet () { return `Hello, ${this.greeting}`; }}let greeter = new Greeter('World');console.log(greeter.greet());复制代码 继承
class Animal { // Animal 是基类或超类 name: string; constructor (name: string) { this.name = name; } move (distanceInMeters: number = 0): string { return `${this.name} moved ${distanceInMeters}m.`; }}class Dog extends Animal { // Dog 是派生类 constructor (name) { super(name); // 执行基类构造函数，访问 this的属性之前，我们 一定要调用 super() } bark (): string { return 'Woof! Woof!'; } move (distanceInMeters = 20): string { return super.move(distanceInMeters); // 基类move方法 }}const dog = new Dog('Lili')console.log(dog.bark());console.log(dog.move(100));复制代码 公共、私有与受保护的修饰符
// public: 成员都默认为 publicclass AnimalPulic { // 明确的将一个成员标记成 public public name: string; public constructor (name: string) { this.name = name; } public move (distanceInMeters: number = 0): string { return `${this.name} moved ${distanceInMeters}m.`; }}// private: 不能在声明它的类的外部访问, private成员在派生类中仍然可以访问class AnimalPrivate { private name: string; // 不能在声明它的类的外部访问 public constructor (name: string) { this.name = name; } public move (distanceInMeters: number = 0): string { return `${this.name} moved ${distanceInMeters}m.`; }}console.log(new AnimalPrivate("Cat").name); // Property 'name' is private and only accessible within class 'AnimalPrivate'.// protected: 与 private修饰符的行为很相似, 但protected成员在派生类中仍然可以访问class Person { protected name: string; protected constructor (name: string) { // 构造函数被标记成protected，这个类不能在包含它的类外被实例化，但是能被继承 this.name = name; }}class Employee extends Person { private department: string; constructor (name, department) { super(name); this.department = department; } public getElevatorPitch(): string { return `Hello, my name is ${this.name} and I work in ${this.department}.`; }} let howard = new Employee('Howard', 'Sales');console.log(howard.getElevatorPitch());console.log(howard.name); // Property 'name' is protected and only accessible within class 'Person' and its subclasses.console.log(new Person("John")); // Constructor of class 'Person' is protected and only accessible within the class declaration.复制代码 readonly修饰符
// 使用 readonly关键字将属性设置为只读的，只读属性必须在声明时或构造函数里被初始化。class Octopus { readonly numberOfLegs: number = 8; constructor (private name: string) {} // 参数name使用了参数属性，在一个地方定义并给初始化一个成员（包括属性和赋值）}let dad = new Octopus('Man with the 8 strong legs');dad.name = 'Man with the 3-piece suit'; // Cannot assign to 'name' because it is a constant or a read-only property.复制代码 存取器：get、set
// 通过getters/setters来截取对对象成员的访问// 只带有 get不带有 set的存取器自动被推断为 readonly// 运行下面代码可能会报：Accessors are only available when targeting ECMAScript 5 and higher.// 解决：在命令后加 --target ES5class EmployeeGetSet { private _fullName: string; get fullName (): string { return this._fullName; } set fullName (_fullName: string) { this._fullName = _fullName; }}let employeeGetSet = new EmployeeGetSet();employeeGetSet.fullName = 'Tom';console.log(employeeGetSet.fullName);复制代码 静态属性
// 存在于类本身上面而不是类的实例上class Gird { static origin = { x: 0, y: 0 } constructor (public scale: number) {} // scale 使用参数属性 calculateDistanceFromOrigin (point: {x: number, y: number}) { let xDist = (point.x - Gird.origin.x); // 静态属性调用 let yDist = (point.y - Gird.origin.y); return Math.sqrt(xDist * xDist + yDist * yDist) / this.scale; }}复制代码 抽象类
// 抽象类做为其它派生类的基类使用，抽象类可以包含成员的实现细节，一般不会直接被实例化。abstract class AnimalAbstract { // 定义抽象类 constructor(public name: string) {} abstract makeSound() : string; // 定义抽象方法，不包含具体实现并且必须在派生类中实现}class Sheep extends AnimalAbstract { constructor(name) { super(name); } makeSound (): string { return `A Sheep named ${name}, sounds mie mie~`; } moved () { return `A Sheep named ${name}, moved 8km`; }}let sheep: AnimalAbstract; // 创建一个对抽象类型的引用sheep = new Sheep('Hary');console.log(sheep.makeSound());console.log(sheep.moved()); // Property 'moved' does not exist on type 'AnimalAbstract'. 因为对象是对抽象类的引用，方法在声明的抽象类中不存在复制代码