类

1. 定义类

   class Person {
       name: string = 'iGma';
       age: number = 20;
   
       run(m: number) {
           console.log(`${this.name}跑步${m}米`);
       }
   }
   
   let per = new Person();
   per.run(100);

2. 静态属性/方法：静态属性或方法不需要 new 类的实例，直接用类名即可调用。

   class Person {
       name: string = 'iGma';
       static age: number = 20;
   
       static run(m: number) {
           console.log('静态方法 run');
       }
   }
   
   console.log(Person.age);
   Person.run(100);

3. 只读属性：只能读不能改

   class Person {
       readonly name: string = 'iGma';
       age: number = 20;
   }
   
   let per = new Person();
   per.name = 'hahaha';    // 报错
   per.age = 21;           // 正常

构造函数

1. 定义

   class Person {
   	// 构造函数
       constructor() {
           console.log(this)
       }
   }

2. 在创建类的实例对象时会执行该函数。此时的 this 就表示当前对象。

3. 可以在这个函数中给属性赋值

   class Person {
       name: string
       age: number
       constructor(name: string, age: number) {
           this.name = name;
           this.age = age;
       }
   }
   
   let per = new Person('iGma', 20);
   console.log(per);

继承

1. 定义

   class Person {
       id: number;
       name: string;
   
       constructor(id: number, name: string) {
           this.id = id;
           this.name = name;
       }
   }
   
   // 教师
   class Teacher extends Person {}
   
   let tea = new Teacher(230713, 'iGma');
   console.log(tea);

2. 方法的重写

   class Person {
       id: number;
       name: string;
   
       constructor(id: number, name: string) {
           this.id = id;
           this.name = name;
       };
   
       run() {
           console.log(`跑步`);
       }
   }
   
   // 教师
   class Teacher extends Person {
       run() {
           console.log(`${this.name}在跑步`);
       }
   }
   
   let tea = new Teacher(230713, 'iGma');
   tea.run();
   console.log(tea);

3. super：子类中使用 super 既是使用父类中的属性或方法。当 super 是一个方法时表示调用父类的构造方法。

   class Person {
       id: number;
       name: string;
   
       constructor(id: number, name: string) {
           this.id = id;
           this.name = name;
       };
   
       run() {
           console.log(`跑步`);
       }
   }
   
   // 教师
   class Teacher extends Person {
       subject: string;
       constructor(id: number, name: string, subject: string) {
           super(id, name);
           this.subject = subject;
           
           super.run();
       }
   }
   
   let tea = new Teacher(230713, 'iGma', '计算机');
   console.log(tea);

抽象类

1. 抽象类不能用来创建对象，它是专门被其他类继承的。

2. 代码

   abstract class Person {
       id: number;
       name: string;
   
       constructor(id: number, name: string) {
           this.id = id;
           this.name = name;
       };
   }
   
   // 教师
   class Teacher extends Person {}
   
   let tea = new Teacher(230713, 'iGma');
   let per = new Person(230714, 'aaa');    // 报错

3. 抽象方法：定义在抽象类中，没有方法体，子类必须重写该方法。

   abstract class Person {
       id: number;
       name: string;
   
       constructor(id: number, name: string) {
           this.id = id;
           this.name = name;
       };
   
       abstract run(): void;
   }
   
   // 教师
   class Teacher extends Person {
       run(): void {
           console.log('跑步');
       }
   }
   
   let tea = new Teacher(230713, 'iGma');
   tea.run();

接口

1. 作用：用来定义类的结构。规定类中应该包含哪些属性和方法。

2. 接口可以重新声明。

3. 接口中的属性和方法不能有实际值。

   interface user {
       name: string;
       age: number;
       run(): void;
   }
   
   class Us implements user {
       name: string;
       age: number;
       constructor(name: string, age: number) {
           this.name = name;
           this.age = age;
       };
       run() {
           console.log(123);
       }
   }