Reflect.decoration与在TypeScript中手动修饰

我有两个装饰师，如下所示：

import "reflect-metadata";

const enum MetadataTypes {
  Type = "design:type",
  Paramtypes = "design:paramtypes",
  ReturnType = "design:returntype"
}

function Decorator1(target: any, key: string): void {
  console.log(`Applied Decorator1 to ${key} on ${target.constructor.name}`);
  const type = Reflect.getMetadata(MetadataTypes.Type, target, key);
  console.log(type.name);
}

function Decorator2(target: any, key: string): void {
  console.log(`Applied Decorator2 to ${key} on ${target.name}`);
  const type = Reflect.getMetadata(MetadataTypes.Type, target, key);
  console.log(type);
}

一种是手动应用的：

export class MyClass {
  @Decorator1
  private foo: string;
}

另一个使用

Reflect.decoration

：

Reflect.decorate([Decorator2], MyClass, "foo");

为什么使用Reflect应用的decorator无法检索数据类型

注销输出为：

Applied Decorator1 to foo on MyClass
String

Applied Decorator2 to foo on MyClass
undefined

---

要使用

Reflect.decort

，您必须通过类的原型来实现类似的行为

import "reflect-metadata";

const enum MetadataTypes {
  Type = "design:type",
  Paramtypes = "design:paramtypes",
  ReturnType = "design:returntype"
}

function Decorator1(target: any, key: string): void {
  console.log(`Applied Decorator1 to ${key} on ${target.constructor.name}`);
  const type = Reflect.getMetadata(MetadataTypes.Type, target, key);
  console.log(type.name);
}

export class MyClass {
  private foo: string;
}

Reflect.decorate([Decorator1], MyClass.prototype, "foo");

// Output:
// Applied Decorator1 to foo on MyClass
// undefined

问题在于，在使用

Reflect.decoration

时，不会生成元数据

使用decorator语法使编译器保存元数据（当启用了配置选项时，

emitdecorormatadata

可以通过

Reflect.getMetadata

访问）

您可以在此处阅读：