类的使用

定义

class Person {
  name: string
  age: number

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

  eating() {
    console.log(this.name + " eating")
  }
}

const p = new Person("why", 18)
console.log(p.name)
console.log(p.age)
p.eating()

export {}

继承

class Person {
  name: string = ""
  age: number = 0

  eating() {
    console.log("eating")
  }
}

class Student extends Person {
  sno: number = 0

  studying() {
    console.log("studying")
  }
}

class Teacher extends Person {
  title: string = ""

  teaching() {
    console.log("teaching")
  }
}

const stu = new Student()
stu.name = "coderwhy"
stu.age = 10
console.log(stu.name)
console.log(stu.age)
stu.eating()

class Person {
  name: string
  age: number

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

  eating() {
    console.log("eating 100行")
  }
}

class Student extends Person {
  sno: number

  constructor(name: string, age: number, sno: number) {
    // super调用父类的构造器
    super(name, age)
    this.sno = sno
  }

  eating() {
    console.log("student eating")
    super.eating()
  }

  studying() {
    console.log("studying")
  }
}

const stu = new Student("why", 18, 111)
console.log(stu.name)
console.log(stu.age)
console.log(stu.sno)

stu.eating()

export {}

多态

class Animal {
  action() {
    console.log("animal action")
  }
}

class Dog extends Animal {
  action() {
    console.log("dog running!!!")
  }
}

class Fish extends Animal {
  action() {
    console.log("fish swimming")
  }
}

class Person extends Animal {

}

// 父类引用指向子类对象(const animal:Animal = new Dog())
// animal: dog/fish
// 多态的目的是为了写出更加具备通用性的代码
function makeActions(animals: Animal[]) {
  animals.forEach(animal => {
    animal.action()
  })
}

makeActions([new Dog(), new Fish(), new Person()])

private修饰符

class Person {
  private name: string = ""

  // 封装了两个方法, 通过方法来访问name
  getName() {
    return this.name
  }

  setName(newName) {
    this.name = newName
  }
}

const p = new Person()
console.log(p.getName())
p.setName("why")

export {}

protected修饰符

// protected: 在类内部和子类中可以访问

class Person {
  protected name: string = "123"
}

class Student extends Person {
  getName() {
    return this.name
  }
}

const stu = new Student()
console.log(stu.getName())

export {}

readonly修饰符

class Person {
  // 1.只读属性是可以在构造器中赋值, 赋值之后就不可以修改
  // 2.属性本身不能进行修改, 但是如果它是对象类型, 对象中的属性是可以修改
  readonly name: string
  age?: number
  readonly friend?: Person
  constructor(name: string, friend?: Person) {
    this.name = name
    this.friend = friend
  }
}

const p = new Person("why", new Person("kobe"))
console.log(p.name)
console.log(p.friend)

// 不可以直接修改friend
// p.friend = new Person("james")
if (p.friend) {
  p.friend.age = 30
} 

// p.name = "123"

getter/setter方法

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

  // 访问器setter/getter
  // setter
  set name(newName) {
    this._name = newName
  }
  // getter
  get name() {
    return this._name
  }
}

const p = new Person("why")
p.name = "coderwhy"
console.log(p.name)

静态成员变量

// class Person {
//   name: string = ""
//   age: number = 12
// }

// const p = new Person()
// p.name = "123"

class Student {
  static time: string = "20:00"

  static attendClass() {
    console.log("去学习~")
  }
}

console.log(Student.time)
Student.attendClass()

抽象类

function makeArea(shape: Shape) {
  return shape.getArea()
}


abstract class Shape {
  abstract getArea(): number
}


class Rectangle extends Shape {
  private width: number
  private height: number

  constructor(width: number, height: number) {
    super()
    this.width = width
    this.height = height
  }

  getArea() {
    return this.width * this.height
  }
}

class Circle extends Shape {
  private r: number

  constructor(r: number) {
    super()
    this.r = r
  }

  getArea() {
    return this.r * this.r * 3.14
  }
}

const rectangle = new Rectangle(20, 30)
const circle = new Circle(10)

console.log(makeArea(rectangle))
console.log(makeArea(circle))
// makeArea(new Shape())

// makeArea(123)
// makeArea("123")

类的类型

class Person {
  name: string = "123"
  eating() {

  }
}

const p = new Person()

const p1: Person = {
  name: "why",
  eating() {

  }
}

function printPerson(p: Person) {
  console.log(p.name)
}

printPerson(new Person())
printPerson({name: "kobe", eating: function() {}})

export {}