Ts有趣现象之“初始化时父类中的属性必须在父类构造器中进行，子类操作无效”

先上正确版本

• 父类Person.ts

  class Person {
      name:string
      age:number
      constructor(name:string,age:number) {
          this.name = name
          this.age = age
      }
  }
  
  export {Person}
  

• 子类Student.ts

  import Action from "../interfaces/Action";
  import {Person} from "./Person";
  import Sex from "../enums/Sex";
  /*子类Student，继承父类Person*/
  class Student extends Person implements Action{
    readonly sex:Sex
    constructor(name:string,age:number,sex:Sex) {
        super(name,age);
        this.sex = sex
    }
    behavior(): void {
        console.log(`${this.name} ${this.age} ${this.sex.valueOf()}`)
    }
  }
  export default Student
  

再说说错误例子

• 父类Person.ts

  class Person {
      name:string
      age:number
  }
  
  export {Person}
  

• 子类Student.ts

  import Action from "../interfaces/Action";
  import {Person} from "./Person";
  import Sex from "../enums/Sex";
  /*子类Student，继承父类Person*/
  class Student extends Person implements Action{
    readonly sex:Sex
    constructor(name:string,age:number,sex:Sex) {
        super();
        this.name = name
        this.age = age
        this.sex = sex
    }
    behavior(): void {
        console.log(`${this.name} ${this.age} ${this.sex.valueOf()}`)
    }
  }
  export default Student
  

有人可能反驳我说，父类中没有定义无参数的constructor，但是我想说，定义了也不好使！请看下面代码，依然是报错不行的！

• 父类Person.ts

  class Person {
      name:string
      age:number
      constructor() {}
  }
  export {Person}
  

• 子类Student.ts

  import Action from "../interfaces/Action";
  import {Person} from "./Person";
  import Sex from "../enums/Sex";
  /*子类Student，继承父类Person*/
  class Student extends Person implements Action{
    readonly sex:Sex
    constructor(name:string,age:number,sex:Sex) {
        super();
        this.name = name
        this.age = age
        this.sex = sex
    }
    behavior(): void {
        console.log(`${this.name} ${this.age} ${this.sex.valueOf()}`)
    }
  }
  export default Student
  

所以我得出结论，初始化类实体时，在constructor中仅能对定义在该类的属性初始化
其实，想要在constructor对父类中的属性初始化，也可以用另一种方式——用接口继承类（Java转来的朋友，不要疑惑，Ts是支持接口继承类的），然后用类实现接口，看下面例子

• 父类Person

  class Person {
      name:string
      age:number
      constructor() {}
  }
  export {Person}
  

• 接口Action.ts

  import {Person} from "../pojo/Person";
  
  interface Action extends Person{
      behavior():void
  }
  export default Action
  

• 子类Student.ts

  import Action from "../interfaces/Action";
  import Sex from "../enums/Sex";
  
  class Student implements Action{
      age: number;
      name: string;
      readonly sex:Sex
      constructor(name:string,age:number,sex:Sex) {
          this.name = name
          this.age = age
          this.sex = sex
      }
      behavior(): void {
          console.log(`${this.name} ${this.age} ${this.sex.valueOf()}`)
      }
  }
  export default Student