如何找到所有装饰有某种装饰的物业? [英] How to find all properties decorated with a certain decoration?

问题描述

我想将装饰器添加到已使用Angular Input 装饰器装饰的属性中.
我需要这个，因为我想为特定的 Component 获得一些(装饰的) Input 属性.

我发现了非常相似的问题，但是有一个很大的区别(我需要属性而不是类，所以我不能在类上引入新变量作为建议的答案).

我想要实现的是:

 导出类BaseComponent{@Input()id:数字;@Input()@isFilter id2:数字；@Input()@isFilter id3:数字；公共getDefaultFilter():对象{令o:部分< this>= {};//将具有装饰器isFilter的this(self)上的所有属性分配给o！返回o；//o应该是{id2:what_is_set，id3:what_is_set}}} 

解决方案

您可以使用 reflect-metadata 将修饰后的属性存储为元数据.例如.以下代码将存储用 @isFilter()修饰的所有属性的名称.然后，您可以调用 getFilteredProperties(this)获得仅包含修饰属性的 this 的浅表副本.

  import'reflect-metadata';const metadataKey = Symbol('isFilter');函数isFilter():(目标:对象，propertyKey:字符串)=>空白 {返回registerProperty;}函数registerProperty(target:object，propertyKey:string):void {let属性:string [] = Reflect.getMetadata(metadataKey，target);如果(属性){properties.push(propertyKey);} 别的 {属性= [propertyKey];Reflect.defineMetadata(metadataKey，属性，目标);}}函数getFilteredProperties(origin:object):object {const属性:string [] = Reflect.getMetadata(metadataKey，origin);const result = {};properties.forEach(key => result [key] = origin [key]);返回结果；} 

您可能还想看看装饰器的TypeScript文档.

更新:由于Plunker目前似乎存在一些技术难题，因此我利用这次机会设置了 Stackblitz 用于上面的代码.仍然可以在此处找到.

I would like to add decorator to property already decorated with Angular Input decorator.
I need this, because I want to get some (those which are decorated) Input properties for specific Component.

I found very similar question here, but with one big difference (I need it for property not class, so I can not introduce new variable on class as accepted answer proposed).

What I want to achieve is:

export class BaseComponent 
{   
    @Input() id: number;
    @Input() @isFilter id2: number;
    @Input() @isFilter id3: number;

    public getDefaultFilter(): object
    {
        let o: Partial<this> = {};

        //Assign all properties on this(self), which has decorator isFilter, to o!!   

        return o;    //o should be {id2: whatever_is_set, id3: whatever_is_set}
    }
}

解决方案

You can use reflect-metadata to store the decorated properties as metadata. E.g. the following code will store the names of all properties decorated with @isFilter(). You can then call getFilteredProperties(this) to get a shallow copy of this containing only the decorated properties.

import 'reflect-metadata';

const metadataKey = Symbol('isFilter');

function isFilter(): (target: object, propertyKey: string) => void {
  return registerProperty;
}

function registerProperty(target: object, propertyKey: string): void {
  let properties: string[] = Reflect.getMetadata(metadataKey, target);

  if (properties) {
    properties.push(propertyKey);
  } else {
    properties = [propertyKey];
    Reflect.defineMetadata(metadataKey, properties, target);
  }
}

function getFilteredProperties(origin: object): object {
  const properties: string[] = Reflect.getMetadata(metadataKey, origin);
  const result = {};
  properties.forEach(key => result[key] = origin[key]);
  return result;
}

You might also want to take a look at the TypeScript documentation for decorators.

Update: Since Plunker appears to have some technical difficulties at the moment I used the opportunity to set up a Stackblitz for the code above. The old Plunker can still be found here.

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