如果使用Angular 2堆栈，则Typescript Reflect.getMetadata('design:type'..)返回Object而不是Date. [英] Typescript Reflect.getMetadata('design:type'..) returns Object instead of Date if the Angular 2 Stack is used

问题描述

以下代码示例按预期运行，并打印出"[功能:日期]"

The following code Sample is working as expected and prints out "[Function: Date]"

import 'reflect-metadata'
function logType(target : any, key : string) {
     var t = Reflect.getMetadata("design:type", target, key);
     console.log(`${key} type: ${t.name}`);
   }
export class Demo {
  @logType // apply property decorator
  test: Date;
}
let demo = new Demo();
console.log(Reflect.getMetadata('design:type', demo, "test"));

如果我在Angular 2项目中放置相同的代码，则会返回"function Object(){[native code]}".

If I place the same code within an Angular 2 Project, "function Object() { [native code] }" is returned.

我为此准备了一个柱塞: https://plnkr.co/edit/DhXT89U0q5fCOWlCrx6w?p=preview

I prepared a Plunker for this: https://plnkr.co/edit/DhXT89U0q5fCOWlCrx6w?p=preview

Reflect.getMetadata('design:type'...)仍适用于自定义类和其他内置类.我只能用Date产生这个问题.

Reflect.getMetadata('design:type' ...) is still working for custom classes and other builtin classes. I could only produce this problem with Date.

我在做什么错了?

推荐答案

您必须执行函数，而不仅仅是将其放置在.)中，您应该在 @logType

You have to execute the function, and not just.. put it there :), you should add parentheses after @logType

export class Demo {
  @logType() // add parentheses 
  test: Date;
}

另一方面，您应该将您的 @logType 函数更改为以下内容:

On the other hand you should change your @logType function to something like this:

function logType(type: any) {
  return function(target: any, propertyKey: string) {  
     Reflect.defineMetadata('design:type', type, target, propertyKey);
  }
}

您可以这样拨打电话:

export class Demo {
  @logType(Date) // apply property decorator
  test: Date;
}

我更新了plnkr以显示我的意思: plnkr

I've updated the plnkr to show what I mean: plnkr

您只能获取具有内置类型的 string ， boolean ， number 或 object . object 是什么，从 Date 到 Array 到您的 Math 和 WeakMap .所有内置函数的求值结果都为 Object ，我不确定这是错误还是设计使然.

You can only get either string, boolean, number or object with the built-in types. Where object will be anything, from Date to Array to your Math and WeakMap. All built-ins will evaluate to Object, I'm not sure if this a bug, or by design.

但是，您可以使用您的方法来获取自定义类.如果愿意的话

You can however use your method to get custom classes. If you would do

export class Demo {
  @logType
  test: Demo;
}

它将打印出 Demo

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