ts中定义类、类的继承、修饰符

首先，简单介绍ES6的class类

class Foo {
	constructor(name,age){ // 实例前的构造函数，实例添加name/age属性
		this.name = name
		this.age = age
	}
	getName () { // 原型添加getName()方法
		return `My name is ${this.name} age : ${this.age}`
	}
}

let foo = new Foo('小明',12) // Foo {name:'小名',age:12,__proto__:getName(){}}

ts定义类：

class Foo {
	public name:string // 需要提前声明值，默认为public
	public age:number
	public constructor(_name:string,_age:number){
		this.name = _name
		this.age = _age
	}
	public getName ():string { // 原型方法，指定返回值为string类型
		return `My name is ${this.name} age : ${this.age}`
	}
}

let foo = new Foo('小明',12) // Foo {name:'小名',age:12,__proto__:getName(){}}

这里指定name和age的类型，附部分类型：

attr : sting // sting类型
attr : number // number类型
attr : boolean // boolean类型
attr : string[] // 数组的每一项必须是string类型
attr : number[] // 数组每一项必须是number类型
attr : Array< any>// 数组每一项可以为任意类型
attr : [string,number] // 数组每一项必须是指定类型
attr ?: string // 非必传

提前声明值可以利用参数属性

class Foo {
	public constructor(public name:string,public age:number){}
	public getName ():void {
		console.log(this.name,this.age)
	}
}
let foo = new Foo(‘小明’,12) // Foo {name:'小明',age:12,__proto__:getName(){}}

介绍public、private、protected、readonly、static 等标识

• public (默认为public，也可以设置为public)

class Foo {
	pulbic name:string
	public constructor (_name?:string) {
		this.name = _name || ''
	}
}
let foo = new Foo('小明') // Foo {name:'小名'}

• private (可以被继承，但是无法在实例中访问)

class Foo {
	private name:string
	constructor (_name:string) {
		this.name = _name
	}
}
let foo = new Foo('小明') // Foo {name:'小名'}
console.log(foo.name) //error: Property 'name' is private;

• protected (与private类似，但是当构造函数是protected时，无法实例化，只能被继承)

class Foo {
	protected name:string
	protected constructor(_name:string){
		this.name = _name
	}
}

let foo = new Foo('小明')  //error: Constructor of class 'Foo' is protected

• readonly (只读属性，无法被修改/克隆)

class Foo {
	readonly name:string
	public constructor(_name:string){
		this.name = _name
	}
}

let foo = new Foo('小明')  // Foo {name:'小明'}
foo.name = '小红' //error: Cannot assign to 'name' because it is a constant or a read-only property.

• static (静态属性，不能被实例访问，在类里面访问时，需要加上类名）

class Foo {
	static age:number = 12
	public constructor(private name:string){}
	pubilc getAge ():void {
		console.log(Foo.age)
	}
}

let foo = new Foo('小明')  // Foo {name:'小明',__proto__:getAge(){}}
console.log(foo.getAge()) // 12 

ts继承：

class Foo {
	public name:string
	public age:number
	public construcor (_name:string,_age:number) {
		this.name = _name
		this.age = _age
	}
	getName ():string {
		return this.name
	}
}

class Bar extends Foo {
	private className:string
	public constructor (_name:string,_age:number,_className:string) {
		super(_name,_age)
		this.calssName = _className
	}
	public getClassName ():void {
		console.log(this.className)
	}
}

let bar = new Bar('小明',12,'一年级') // Bar {name:'小明',age:12,className:'一年级'}
console.log(bar.getName()) // 小明
console.log(bar.getClassName()) // 一年级