接口

接口的关键字interface

interface IStudent {
    name: string
    no: number
}

function say(stu: IStudent) {
    console.log(stu)
}
say({ name: 'hhh', no: 1 })

可选属性

interface IStudent {
    name: string
    no: number
    tag?: string //可选属性
}

function say(stu: IStudent) {
    console.log(stu)
}
say({ name: 'hhh', no: 1 })
say({ name: 'haha', no: 2, tag: '三好学生' })

只读属性 ,关键字 readonly

interface IStudent {
    readonly firtName: string
    name: string
    no: number
    tag?: string
}

function say(stu: IStudent) {
    console.log(stu)
}
let stu1: IStudent = { name: '张三', no: 1, firtName: '张' }
let stu2: IStudent = { name: '李四', no: 2, tag: '三好学生', firtName: '李' }
// stu1.firtName = '王'
console.log(stu1.firtName)
say(stu1)
say(stu2)

用接口声明函数

interface ISay1 {
    (name: string): string
}
let say1: ISay1 = (str1: string) => { return str1 }
let say2: ISay1 = (str1: string) => { return str1 }
// function say1(st1: string): string {
//     return st1
// }
console.log(say1('say1'), say2('say2'))

可索引类型的接口

声明的数组

interface StringArray {
    [index: number]: string;
}
let myArray: StringArray;
myArray = ["Bob", "Fred"];

声明的map

interface IMap {
    [key: string]: string;
}
let m: IMap = { "a": "a" }
console.log(m)

类类型,接口对class的约束

// 接口重在约束
interface ILee {
    firstname: string
}

class Lee implements ILee {
    firstname: string
}
let lee = new Lee()
lee.firstname = 'Lee'

console.log(lee)

接口的继承

interface IAnimal {
    name: string
}
interface ICat extends IAnimal {
    say(str: string): string
}
interface IDog extends IAnimal {
    say(str: string, s2: string): string
}
class Cat implements ICat {
    name: string
    say(s1: string): string {
        return s1
    }
}
// 接口重在签名，也就是约束
class Dog implements IDog {
    name: string
    say(s1: string, st2: string): string {
        return s1 + st2
    }
}
let cat: ICat = new Cat()
console.log(cat.say('cat'))
let dog: IDog = new Dog()
console.log(dog.say('dog1', 'dog2'))