类型兼容依据。。。

来源：3-14 类 - 公共，私有与受保护修饰符+ readonly 修饰符

旋涡鸣人_

2019-05-29

Property ‘move’ is missing in type ‘Employee’ but required in type ‘Animal’.ts(2741)
test.ts(89, 3): ‘move’ is declared here.

class Animal {
  private name: string
  constructor(name: string) {
    this.name = name
  }

  move(distance: number = 0) {
    console.log(`$(this.name) moved ${distance}m`)
  }
}

class Rhino extends Animal {
  constructor() {
    super('Rhino')
  }
}

class Employee {
  private name: string
  constructor(name: string) {
    this.name = name
  }
}

let animal = new Animal('Goat')
let rhino = new Rhino()
let employee = new Employee('Bob')

animal = rhino
animal = employee

也就是说某个变量具有了某个类型之后不能轻易改变其类型了吗？

还是要判断类型是否兼容？
父类型一定兼容子类类型 animal = rhino
子类型不一定兼容父类型 rhino = animal (是不是要做个类型diff啊，有啥原则吗)

animal = employee 这个就提示

Type ‘Employee’ is not assignable to type ‘Animal’.
Types have separate declarations of a private property ‘name’.

理解起来还是很别扭。。

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