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类的注解方式
- 需要对实例的属性进行注解。
- 类的方法中有参数的需要进行注解。
class Greeter { greeting: string; constructor(message: string) { this.greeting = message; } greet() { return "Hello, " + this.greeting; } } let greeter = new Greeter("world"); 复制代码
继承中的super
1. 构造函数内部的super指的是父类的构造函数
class Animal { name: string; constructor(theName: string) { this.name = theName; } move(distanceInMeters: number = 0) { console.log(`${this.name} moved ${distanceInMeters}m.`); } } class Snake extends Animal { constructor(name: string) { super(name); } move(distanceInMeters = 5) { console.log("Slithering..."); super.move(distanceInMeters); } } let sam = new Snake("Sammy the Python"); sam.move(); 复制代码
类成员的修饰符
1. public：公共的成员属性
- 自身可以调用
- 实例可以调用
- 子类可以调用
class Animal { public name: string; public constructor(theName: string) { this.name = theName; } public move(distanceInMeters: number) { console.log(`${this.name} moved ${distanceInMeters}m.`); } } 复制代码
2. private : 只有自身可以调用
class Animal { private name: string; constructor(theName: string) { this.name = theName; } } new Animal("Cat").name; // 错误: 'name' 是私有的. 复制代码
3. protected: 自身可以调用，子类也可以调用，但是实例不可以调用
class Person { protected name: string; constructor(name: string) { this.name = name; } } class Employee extends Person { private department: string; constructor(name: string, department: string) { super(name) this.department = department; } public getElevatorPitch() { 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); // 错误 复制代码
readonly修饰符
readobly关键字将属性设置为只读，这个属性必须在声明或者构造函数中被初始化。readonly不能对方法进行修饰。
class Octopus { readonly name: string; readonly numberOfLegs: number = 8; constructor (theName: string) { this.name = theName; } } let dad = new Octopus("Man with the 8 strong legs"); dad.name = "Man with the 3-piece suit"; // 错误! name 是只读的. 复制代码
参数属性
参数属性本质上就是一种简写的首发，就是将声明和赋值合并在一处。下面两种方式其实是等价的。
// 方式1 class Octopus { readonly numberOfLegs: number = 8; constructor(readonly name: string) { } } // 方式2 class test { readonly numerOfLegs: number = 8; readonly name: string; constructor(Thename: string) { this.name = Thename; } }
