class类

TS是如何定义类的 一定要在构造器前定义变量并且一定要是构造器参数含有的变量 构造器不强制定义

tsx

//代码会报错 因为在ts中不能直接在constructor里定义变量的 需要提前在constructor上面先声明
class Person {
  constructor(name: string, age: number) {
    this.name = name//no
    this.age = age//no
  }
}
//代码正确
class Person {
  name: string
  age: number
  constructor(name: string, age: number) {
    this.name = name//yes
    this.age = age//yes
  }
}
//代码正确，可以不定义构造器 但是要初始化类里的变量
class Person {
  name: string = 'zmz'
  age: number = 18
}
const p1: Person = { name: 'zmz', age: 18 }

属性的简写形式

tsx

//完整写法
class Person {
  public name: string
  public age: string
  constructor(name: string, age: string) {
    this.name = name
    this.age = age
  }
}
//简写形式
class Person {
  constructor(name: string, age: number) { }
}

类的三个修饰 public private protected

使用public 修饰符可以让你定义的变量内部访问也可以外部访问如果不写默认就是public

使用 private 修饰符代表定义的变量私有的只能在内部访问不能在外部访问

使用 protected 修饰符代表定义的变量私有的只能在内部和继承的子类中访问不能在外部访问

tsx

class Person {
  public name: string
  private age: number
  protected sex: string
  constructor(name: string, age: number, sex: string) {
    this.name = name
    this.age = age
    this.sex = sex
  }
  run() {}
}
const p: Person = new Person('张三', 18, '男')
p.name = '李四'//ok
p.age = 20//no 私有属性 只能在Person类中访问
p.sex = '女'//no 保护属性 只能在Person类和其子类中访问

readonly修饰符

tsx

class Car {
  constructor(
    public readonly vin: string,//车辆识别码，为只读属性
    public readonly year: number,//出厂年份，为只读属性
    public color: string,
    public sound: string
  ) { }
  //打印车辆信息
  displayInfo() {
    console.log(`
      识别码：${this.vin},
      出⼚年份：${this.year},
      颜⾊：${this.color},
      ⾳响：${this.sound}
      `)
  }
}
const car = new Car('1HGCM82633A123456', 2018, '⿊⾊', 'Bose响');
// 以下代码均错误：不能修改readonly属性
// car.vin = '897WYE87HA8SGDD8SDGHF';
// car.year = 2020;

static静态属性和静态方法

我们使用static定义的属性不能用this去访问只能用类名.属性

tsx

class Person {
  public name: string
  private age: number
  protected sex: string
  static nb: string
  constructor(name: string, age: number, sex: string) {
    this.name = name
    this.age = age
    this.sex = sex
  }
  run() {}
}
const p: Person = new Person('张三', 18, '男')
p.name = '李四'
Person.nb = '123'

static 静态函数同样也是不能通过this 去调用也是通过类名去调用

tsx

class Person {
  public name: string
  private age: number
  protected sex: string
  static nb: string
  constructor(name: string, age: number, sex: string) {
    this.name = name
    this.age = age
    this.sex = sex
    this.run() //no
  }
  static run() {
    return console.log('run')
  }
}
const p: Person = new Person('张三', 18, '男')
p.name = '李四'
Person.nb = '123'
Person.run() //ok

需要注意的是：两个函数都是静态的static是可以通过this互相调用的

tsx

class Person {
  public name: string
  private age: number
  protected sex: string
  static nb: string
  constructor(name: string, age: number, sex: string) {
    this.name = name
    this.age = age
    this.sex = sex
  }
  static run() {
    this.eat()
    return console.log('run')
  }
  static eat() {
    this.run()
    console.log('eat')
  }
}
const p: Person = new Person('张三', 18, '男')
p.name = '李四'
Person.nb = '123'
Person.run() //ok

interface定义类

ts interface 定义类使用关键字 implements 后面跟interface的名字多个用逗号隔开继承还是用extends

接口里的成员都要去实现被继承类中如果有构造器则要继承类里的构造器中写出super()方法同时传参

参数必须是被继承类中有的形参其成员可以不强制实现

tsx

interface PersonClssOne {
  get(type: boolean): boolean
}
interface PersonClssTwo {
  set(): void
  zmz: number
}
class A {
  name: string
  constructor(name: string) {
    this.name = name
  }
  A(): void {}
}
class Person extends A implements PersonClssOne, PersonClssTwo {
  name: string

  constructor(name: string) {
    super('张三')
    this.name = name
  }
  set(): void {
    console.log('set')
  }
  zmz: number
  get(type: boolean): boolean {
    return type
  }
}
let person: Person = new Person('张三呀')

抽象类abstract

abstract用于定义抽象类和抽象方法

抽象类是不可以被实例化的可以被继承

抽象类中的抽象方法必须被子类实现

tsx

abstract class Animal {
  public name: string
  public age: number
  constructor(name: string) {
    this.name = name
  }
  public abstract eat(): void
}

class Dog extends Animal {
  name: string
  constructor(name: string) {
    super(name)
    this.name = name
  }
  public eat() {
    console.log('eat...')
  }
}
let dog: Animal = new Animal('dog')//no
let dog2: Dog = new Dog('dog2')//yes
let dog3: Animal = new Dog('dog3')//yes

class类 ​

class类