装饰器是一种特殊类型的声明，它能够被附加到类声明，方法， 访问符，属性或参数上。

类装饰器

const classDec: ClassDecorator = (target: Function) => {
  target.prototype.myClassName = "类装饰器";
  target.prototype.getClassName = <T>(params: T, param2: number) => {
    console.log(`我是方法里的${params}${param2}`);
    return params;
  };
};

@classDec
class MyClassD {}

let myClassD = new MyClassD();

// console.log(myClassD)
// console.log((myClassD as any).myClassName)
// console.log((myClassD as any).getClassName(123,'zhang'));

工厂装饰器
其实也就是一个高阶函数 外层的函数接受值 里层的函数最终接受类的构造函数
⭐相同函数名称只执行先注册的

const facDec = (params:string): ClassDecorator => {
  return (fun:Function)=>{
    fun.prototype.say = ()=>{
        console.log(`i say${params}`)
    }
  };
};

@facDec('世界和平')
class MyFacDec{
    say(){

    }
}

let myFacDec = new MyFacDec()
myFacDec.say()

装饰器组合

@watcher2('myYname')
@watcher
class AA {
    constructor() {
 
    }
}
 
const aaTest = new AA();
console.log((aaTest as any).getParams('123wode'));
console.log((aaTest as any).getOptions());

方法装饰器

//普通方法装饰器
const methodDec: MethodDecorator = (
  target,
  propertyKey,
  descriptor: PropertyDescriptor
) => {
  const method = descriptor.value;
  descriptor.value = () => {
    console.log(`重写方法`);
  };
};
//静态方法装饰器
const staticMethodDec: MethodDecorator = (
  target,
  propertyKey,
  descriptor: PropertyDescriptor
) => {
  const method = descriptor.value;
  descriptor.value = () => {
    console.log(`重写静态方法`);
  };
};

class MyMethod {
  @methodDec
  public showMethod() {
    console.log(`来吧展示普通方法`);
  }
  @staticMethodDec
  public static showStaticMethod() {
    console.log(`来吧展示静态方法`);
  }
}

let myMethodD = new MyMethod();

// console.log(myMethodD)
// myMethodD.showMethod()

// MyMethod.showStaticMethod()

属性装饰器

const proDec: PropertyDecorator = (target, propertyKey) => {
  let myvalue: string;
  Object.defineProperty(target, propertyKey, {
    get() {
      return myvalue.toLocaleLowerCase();
    },
    set(v) {
      myvalue = v;
    },
  });
};
class Student {
  @proDec
  public name: string;
  public age: number;
  constructor(n: string, a: number) {
    this.name = n;
    this.age = a;
  }
  say() {
    console.log(`${this.name}age is ${this.age}`);
  }
}

let xiaogang = new Student("ZhAngsan", 19);
// xiaogang.say()
// console.log(xiaogang.name)

元数据

Reflect.defineMetadata("myname", "12", myFacDec,'title');
console.log(Reflect.getMetadata("myname",myFacDec,'title'))