• 周一. 8月 15th, 2022

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696 TypeScript类的使用:类的定义,继承,多态,成员修饰符,readonly,getters/setters,静态成员,抽象类abstract,抽象类演练,类的类型

admin

11月 28, 2021

认识类的使用


类的定义


类的继承


类的成员修饰符


只读属性readonly


getters/setters


静态成员


抽象类abstract


抽象类演练


类的类型


01_类的定义.ts

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 {}

02_类的继承.ts

class Person {
  // 【记得初始化赋值。】
  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 = 'hahaha'
stu.age = 10
console.log(stu.name)
console.log(stu.age)
stu.eating()

03_类的继承2.ts

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constructor
    super(name, age)
    this.sno = sno
  }

  // 【重写父类的方法。】
  eating() {
    console.log('student eating')
    super.eating() // 【重写的同时,还可以调用父类的eating方法。】
  }

  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 {}

04_类的多态.ts

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 {}

// 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()])

export {}

05_成员的修饰符-private.ts

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: string) {
    this.name = newName
  }
}

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

export {}

06_成员的修饰符-protected.ts

// 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 {}

07_属性的只读-readonly.ts

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"

08_getters-setter.ts

class Person {
  private _name: string // 规范:一般私有属性前会加_
  
  constructor(name: string) {
    this._name = name
  }

  // 访问器setter/getter 【其实不是函数。】
  // setter
  set name(newName) {
    this._name = newName
  }
  // getter
  get name() {
    return this._name
  }
}

const p = new Person('why')
p.name = 'hahaha'
console.log(p.name)

export {}

09_类的静态成员.ts

// 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()

10_抽象类abstract.ts

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

abstract class Shape {
  // 【1、函数不应该有实现的时候,应该把函数定义为抽象函数。 2、抽象函数可以没有函数体。3、抽象函数要定义在抽象类里。 4、抽象类不能被实例化。 5、抽象类里的方法必须被子类实现,否则子类也要写成抽象类。】
  abstract getArea() // 【编译失败,应该在getArea()后加 : number。】
}

class Rectangle extends Shape {
  private  number
  private height: number

  constructor( number, height: number) {
    super() // 【即使父类没有属性,也要调用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()) // 【抽象类不能被实例化。】

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

11_类的类型.ts

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 {}

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