TypeScript Mixin 混合模式实战：解决多继承与灵活对象扩展

// 声明一个汽车类Vehicle，它有drive方法
class Vehicle {
  drive(): void {
    console.log('驾驶')
  }
}
// 声明轿车类Car，它有work方法
class Car extends Vehicle{
  work(): void {
    console.log('上班代步')
  }
}
// 声明越野车类Suv，它有cross方法
class Suv extends Vehicle{
  cross(): void {
    console.log('山地越野')
  }
}
// 声明跨界车类Crossover, 继承Car和Suv,既可以上班代步，也可以山地越野
class Crossover extends Car, Suv{ // 这里ts报错：Classes can only extend a single class. 子类只能继承一个父类
}

class Vehicle {
    drive(): void {
      console.log('驾驶')
    }
  }
  // 声明轿车类Car，它有work方法
  class Car extends Vehicle{
    work(): void {
      console.log('上班代步')
    }
    getSpace(): void {
        console.log('small');
    }
  }
  // 声明越野车类Suv，它有cross方法
  class Suv extends Vehicle{
    cross(): void {
      console.log('山地越野')
    }
    getSpace(): void {
        console.log('big');
    }
  }
  // 声明跨界车类Crossover, 继承Car和Suv,既可以上班代步，也可以山地越野
  class Crossover extends Vehicle {
  }
  // 这里需要创建需要合并类（Crossover）的同名接口，并继承多个类Car、Suv
  interface Crossover extends Car, Suv {}
  applyMixins(Crossover, [Car, Suv])
  let crossover = new Crossover()
  // 该混合函数摘自TypeScript官方手册，如果derivedCtor和constructors类中存在同名方法，则后者覆盖前者
  function applyMixins(derivedCtor: any, constructors: any[]) {
    constructors.forEach((baseCtor) => {
      Object.getOwnPropertyNames(baseCtor.prototype).forEach((name) => {
        Object.defineProperty(
          derivedCtor.prototype,
          name,
          Object.getOwnPropertyDescriptor(baseCtor.prototype, name) ||
          Object.create(null)
        );
      });
    });
  }
  crossover.drive() // 驾驶
  crossover.work() // 上班代步
  crossover.cross() // 山地越野
  crossover.getSpace() // big，同名方法getSpace是Suv中的，applyMixins函数传入的第二个参数数组最后一个类是Suv

interface AnimalConfig {
    type: string
    name: string
    voice: string
}
class AnimalSpeak {
    speak(config: AnimalConfig): void {
        const {type, name, voice} = config
        console.log(`${type + name}的叫声是${voice}~`);
    }
    dogSpeak(name: string): void {
        console.log(`小狗${name}的叫声是汪汪~`);
    }
    catSpeak(name: string): void {
        console.log(`小猫${name}的叫声是喵喵~`);
    }
}
function extend<T, U>(to: T, from: U) {
    for (const key in from) {
        ;(to as T & U)[key] = from[key] as any
    }
    return to as T & U
}
const context = new AnimalSpeak()
const instance = AnimalSpeak.prototype.speak.bind(context)
extend(instance, context)
instance({type: '小猫', name: '咪咪', voice: '喵喵'}) // 小猫咪咪的叫声是喵喵~
instance.dogSpeak('哮天犬') // 小狗哮天犬的叫声是汪汪~