一、面向对象

封装、继承、多态

1-1 封装函数

api 应用程序接口 封装复杂，接口简单

class Person{
    name:string;
    age;number;
    constructor(name:string,age:number){
        this.name = name;
        this.age = age
    }
    sayName(){
        console.log(this.name);
    }
}

1-2 extends 继承

/* 1、定义一个Person类，包含name,age两个属性 */
class Person{
    name:string;
    age;number;
    constructor(name:string,age:number){
        this.name = name;
        this.age = age
    }
    sayName(){
        console.log(this.name);
    }
}
/* 2、student skill，saySkill */
/* class Student{
    name:string;
    age;number;
    skill:string;
    constructor(name:string,age:number,skill:string){
        this.name = name;
        this.age = age
        this.skill = skill;
    }
    saySkill():void{
        console.log(this.skill);
    }
} */
class Student extends Person{
    skill:string;
    constructor(name:string,age:number,skill:string){
        /* super指的是父类，只能放在子类构造方法中的第一行 */
        super(name,age);
        this.skill = skill;
    }
    saySkill():void{
        console.log(this.skill);
    }
}
var res:Student = new Student("lisi",18,"vue");
console.log(res);
res.sayName();

1-3 多态

根据传入的对象，动态决定调用谁的方法

interface Animal{
    eat():void;
}
class Cat implements Animal{
    eat():void{
        console.log("鱼");
    }
}
class Dog implements Animal{
    eat():void{
        console.log("骨头");
    }
}
class Farmer{
    feed(obj:Animal){
        obj.eat()
    }
}
var f:Farmer = new Farmer();
f.feed(new Cat())
f.feed(new Dog())

二、接口到底是什么

2-1 抽象类

/* 抽象类 */
/* 1、使用class关键字定义的叫实体类 */
/* class Animal{
    eat():void{
        console.log("any");
    }
} */
/* 2、抽象类 本质上就是一个接口 */
abstract class Animal{
    abstract eat():void
}
/* 使用实体类对抽象类实现继承的时候，必须重写抽象类中的抽象方法 */
class Cat extends Animal{
    eat():void{
        console.log("鱼");
    }
}

interface Animal{
    eat():void;
}
class Cat implements Animal{
    eat():void{
        console.log("鱼");
    }
}

三、修饰符public,private,protected

//protected
class Student{
    protected name:string = "lisi";
    sayName(){
        console.log(this.name);
    }
}
var s:Student = new Student();
console.log(s.name);

class Student{
    protected name:string = "lisi";
    sayName(){
        console.log(this.name);
    }
}
/* protected和private的区别：在子类中
    protected可以访问
    private不可以访问
*/
class MidStundet extends Student{
    getName(){
        console.log(this.name);
    }
}
var m:MidStundet = new MidStundet();
m.getName()