类的继承

// TypeScript 5.x

// 基类（父类）
class Animal {
  name: string

  constructor(name: string) {
    this.name = name
  }

  move(distance: number = 0): void {
    console.log(`${this.name} 移动了 ${distance} 米`)
  }
}

// 派生类（子类）
class Dog extends Animal {
  breed: string

  constructor(name: string, breed: string) {
    super(name) // 调用父类构造函数
    this.breed = breed
  }

  bark(): void {
    console.log('汪汪！')
  }
}

const dog = new Dog('旺财', '柴犬')
dog.move(10) // 旺财 移动了 10 米
dog.bark() // 汪汪！
console.log(dog.name, dog.breed) // 旺财 柴犬

class Parent {
  value: number

  constructor(value: number) {
    this.value = value
  }
}

class Child extends Parent {
  extra: string

  constructor(value: number, extra: string) {
    // 必须在访问 this 之前调用 super
    super(value)
    this.extra = extra
  }
}

// 如果子类没有构造函数，会自动调用 super
class SimpleChild extends Parent {
  // 自动生成 constructor(...args) { super(...args) }
}

class Animal {
  name: string

  constructor(name: string) {
    this.name = name
  }

  speak(): void {
    console.log(`${this.name} 发出声音`)
  }
}

class Cat extends Animal {
  speak(): void {
    super.speak() // 调用父类方法
    console.log('喵喵！')
  }
}

const cat = new Cat('咪咪')
cat.speak()
// 咪咪 发出声音
// 喵喵！

class Shape {
  color: string

  constructor(color: string) {
    this.color = color
  }

  getArea(): number {
    return 0
  }

  describe(): string {
    return `一个 ${this.color} 的图形`
  }
}

class Circle extends Shape {
  radius: number

  constructor(color: string, radius: number) {
    super(color)
    this.radius = radius
  }

  // 重写 getArea
  getArea(): number {
    return Math.PI * this.radius ** 2
  }

  // 重写 describe
  describe(): string {
    return `一个 ${this.color} 的圆，半径 ${this.radius}`
  }
}

class Rectangle extends Shape {
  width: number
  height: number

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

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

  describe(): string {
    return `一个 ${this.color} 的矩形，${this.width}x${this.height}`
  }
}

class Base {
  greet(): void {
    console.log('Hello')
  }
}

class Derived extends Base {
  override greet(): void {
    console.log('Hi')
  }

  // ❌ 错误：父类没有这个方法
  // override nonexistent(): void { }
}

// 在 tsconfig.json 中启用严格检查
// "noImplicitOverride": true

abstract class Vehicle {
  abstract brand: string

  // 抽象方法：没有实现
  abstract start(): void
  abstract stop(): void

  // 普通方法：有实现
  honk(): void {
    console.log('Beep!')
  }
}

class Car extends Vehicle {
  brand = 'Toyota'

  start(): void {
    console.log(`${this.brand} 启动`)
  }

  stop(): void {
    console.log(`${this.brand} 停止`)
  }
}

// const vehicle = new Vehicle();  // ❌ 错误：不能实例化抽象类
const car = new Car()
car.start() // Toyota 启动
car.honk() // Beep!

abstract class DataSource {
  // 抽象属性
  abstract name: string
  abstract readonly type: string

  // 抽象方法
  abstract connect(): Promise<void>
  abstract disconnect(): Promise<void>
  abstract query(sql: string): Promise<unknown[]>

  // 抽象 getter
  abstract get isConnected(): boolean

  // 普通方法
  log(message: string): void {
    console.log(`[${this.name}] ${message}`)
  }
}

class MySQLDataSource extends DataSource {
  name = 'MySQL'
  readonly type = 'relational'
  private connected = false

  get isConnected(): boolean {
    return this.connected
  }

  async connect(): Promise<void> {
    this.connected = true
    this.log('Connected')
  }

  async disconnect(): Promise<void> {
    this.connected = false
    this.log('Disconnected')
  }

  async query(sql: string): Promise<unknown[]> {
    this.log(`Executing: ${sql}`)
    return []
  }
}

class Animal {
  name: string

  constructor(name: string) {
    this.name = name
  }

  eat(): void {
    console.log(`${this.name} is eating`)
  }
}

class Mammal extends Animal {
  furColor: string

  constructor(name: string, furColor: string) {
    super(name)
    this.furColor = furColor
  }

  nurse(): void {
    console.log(`${this.name} is nursing`)
  }
}

class Dog extends Mammal {
  breed: string

  constructor(name: string, furColor: string, breed: string) {
    super(name, furColor)
    this.breed = breed
  }

  bark(): void {
    console.log('Woof!')
  }
}

const dog = new Dog('Rex', 'brown', 'German Shepherd')
dog.eat() // 来自 Animal
dog.nurse() // 来自 Mammal
dog.bark() // 来自 Dog

class Parent {
  public publicProp = 'public'
  protected protectedProp = 'protected'
  private privateProp = 'private'

  protected protectedMethod(): void {
    console.log('Protected method')
  }

  private privateMethod(): void {
    console.log('Private method')
  }
}

class Child extends Parent {
  accessProps(): void {
    console.log(this.publicProp) // ✅
    console.log(this.protectedProp) // ✅
    // console.log(this.privateProp);  // ❌ 不能访问

    this.protectedMethod() // ✅
    // this.privateMethod();  // ❌ 不能访问
  }

  // 可以改变 protected 为 public
  public protectedMethod(): void {
    super.protectedMethod()
    console.log('Extended protected method')
  }
}

class Base {
  static count = 0
  static increment(): void {
    Base.count++
  }
}

class Derived extends Base {
  static additionalMethod(): void {
    console.log(`Count: ${Derived.count}`) // 继承静态属性
    Derived.increment() // 继承静态方法
  }
}

Derived.increment()
console.log(Derived.count) // 1

abstract class DataProcessor {
  // 模板方法
  process(): void {
    this.validate()
    this.transform()
    this.save()
    this.notify()
  }

  // 抽象步骤：子类必须实现
  protected abstract validate(): void
  protected abstract transform(): void
  protected abstract save(): void

  // 可选步骤：有默认实现
  protected notify(): void {
    console.log('Processing complete')
  }
}

class UserDataProcessor extends DataProcessor {
  protected validate(): void {
    console.log('Validating user data...')
  }

  protected transform(): void {
    console.log('Transforming user data...')
  }

  protected save(): void {
    console.log('Saving user data...')
  }

  protected notify(): void {
    super.notify()
    console.log('Sending email notification')
  }
}

const processor = new UserDataProcessor()
processor.process()

abstract class PaymentStrategy {
  abstract name: string
  abstract pay(amount: number): Promise<boolean>

  formatAmount(amount: number): string {
    return `$${amount.toFixed(2)}`
  }
}

class CreditCardPayment extends PaymentStrategy {
  name = 'Credit Card'

  constructor(private cardNumber: string) {
    super()
  }

  async pay(amount: number): Promise<boolean> {
    console.log(`Paying ${this.formatAmount(amount)} with ${this.name}`)
    return true
  }
}

class PayPalPayment extends PaymentStrategy {
  name = 'PayPal'

  constructor(private email: string) {
    super()
  }

  async pay(amount: number): Promise<boolean> {
    console.log(`Paying ${this.formatAmount(amount)} with ${this.name}`)
    return true
  }
}

// 接口：纯类型约束，无实现
interface Flyable {
  fly(): void
}

// 抽象类：可以有部分实现
abstract class Bird {
  abstract fly(): void // 抽象方法

  eat(): void {
    // 具体实现
    console.log('Eating')
  }
}

// 类可以实现多个接口，但只能继承一个类
class Sparrow extends Bird implements Flyable {
  fly(): void {
    console.log('Flying')
  }
}

class Parent {
  constructor(public value: number) {}
}

class Child extends Parent {
  constructor(
    value: number,
    public extra: string
  ) {
    super(value) // 必须调用
  }
}

// 如果没有构造函数，自动继承父类构造函数
class SimpleChild extends Parent {}
const child = new SimpleChild(42)

class Final {
  private constructor() {} // 私有构造函数

  static create(): Final {
    return new Final()
  }
}

// class Extended extends Final {}  // ❌ 无法继承