Angularfire2获取已添加对象的键

import { Component } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';

@Component({
  selector: 'app-example',
  template: `
    <button (click)="addObject()">Add Object</button>
    <ul>
      <li *ngFor="let item of items | async">
        Key: {{ item.key }} - Value: {{ item.payload.val() }}
      </li>
    </ul>
  `,
})
export class ExampleComponent {
  items: any;

  constructor(private db: AngularFireDatabase) {
    this.items = db.list('objects').snapshotChanges();
  }

  addObject() {
    const object = { name: 'Example Object' };
    this.db.list('objects').push(object);
  }
}