Question

我尝试扩展Material 2 sidenav组件，以便在关闭之前添加所需的确认。经过大量搜索后，我发现了一种扩展装饰器的潜在方法，因此我不必复制/重写扩展组件的模板和样式：

Extending component decorator with base class decorator

不幸的是，我收到了错误：

Cannot read property '0' of undefined

就行：

const parentAnnotation = parentAnnotations[0];

当我尝试使用该解决方案时。我究竟做错了什么？

继承我的代码：

import { MdSidenav } from '@angular/material';
import { Component, OnInit } from '@angular/core';
import 'zone.js';
import 'reflect-metadata';

function isPresent(obj: any): boolean {
    return obj !== undefined && obj !== null;
  }

export function CustomComponent(annotation: any) {
  return function (target: Function) {
    const parentTarget = Object.getPrototypeOf(target.prototype).constructor;
    console.log(Reflect.getMetadataKeys(parentTarget));
    const parentAnnotations = Reflect.getMetadata('annotations', parentTarget);

    const parentAnnotation = parentAnnotations[0];
    Object.keys(parentAnnotation).forEach(key => {
      if (isPresent(parentAnnotation[key])) {
        // verify is annotation typeof function
        if (typeof annotation[key] === 'function'){
          annotation[key] = annotation[key].call(this, parentAnnotation[key]);
        }else if (
          // force override in annotation base
          !isPresent(annotation[key])
        ){
          annotation[key] = parentAnnotation[key];
        }
      }
    });

    const metadata = new Component(annotation);

    Reflect.defineMetadata('annotations', [ metadata ], target);
  };
}

@CustomComponent({
  selector: 'xw-sidenav'
})
export class XwSidenavComponent extends MdSidenav {


}

延伸角材料2组件

0 个答案: