Firestore 如何从另一个集合文档 id 中获取集合值被引用 [英] Firestore how to get the collection value from another collection document id is referenced

问题描述

我有两个带有以下参考图片的消防商店系列.我想获得 firstName 和 title.这里的 signup_id 引用自 coll-signup 文档 ID.下面给出了我所做的代码.

I have two fire store collection with following reference image . I want to get the firstName and title. Here signup_id is referenced from coll-signup document id. Following code given below what i did.

模型 feed.ts

export interface Feed {
    firstName? : string;
    signup_id? : string;
    title? : string;
}

新闻提要.组件模板

    <ul *ngFor="let feed of feeds">
<!-- <li>{{feed.firstName}}</li> --> // Here I want to print my first name
      <li>{{feed.title}}</li>
      <li>{{feed.signup_id}}</li>
    </ul>

news-feed.component.ts

news-feed.component.ts

import { Component, OnInit } from '@angular/core';
import { Feed } from '../../models/feed';
import { FeedService } from '../../services/feed.service';
@Component({
  selector: 'app-news-feed',
  templateUrl: './news-feed.component.html',
  styleUrls: ['./news-feed.component.css']
})
export class NewsFeedComponent implements OnInit {
  feeds : Feed[];
  constructor(private feedService: FeedService) { }

  ngOnInit() {
    this.feedService.sellectAllNews().subscribe(feeds => {
      this.feeds = feeds;
    })
  }

}

feed.service.ts

feed.service.ts

    import { AngularFirestore, AngularFirestoreCollection, AngularFirestoreDocument } from 'angularfire2/firestore';
    import { Observable } from 'rxjs/Observable';
    import { Feed } from '../models/feed';
    @Injectable()
    export class FeedService {
      feedCollection : AngularFirestoreCollection<Feed>;
      feedItem : Observable<Feed[]>;
    
      constructor(private afs : AngularFirestore) { 
        this.collectionInitialization();
      }
    
      collectionInitialization() {
// I think here I have to modify or add next collection to will get the output
        this.feedCollection = this.afs.collection('col-challange');
        this.feedItem = this.feedCollection.stateChanges().map(changes => {
          return changes.map(a => {
            const data = a.payload.doc.data() as Feed;
            return data;
          })
        })
    
      }
      sellectAllNews() {
        this.collectionInitialization();
        return this.feedItem;
      }
    }

这可以做防火商店吗?我是消防店的新手.请帮助我.谢谢！

this is possible to do fire store? I'm newbie in fire store.Please help me. Thanks!

推荐答案

您需要合并两个集合.

试试这个代码

this.feedCollection = this.afs.collection('col-challange');
this.feedItem = this.feedCollection.snapshotChanges().map(changes => {
      return changes.map(a => {
        //here you get the data without first name
        const data = a.payload.doc.data() as Feed;
        //get the signup_id for getting doc from coll-signup
        const signupId = data.signup_id;
        //get the related document
        return afs.collection('coll-signup').doc(signupId).snapshotChanges().take(1).map(actions => {
          return actions.payload.data();
        }).map(signup => {
          //export the data in feeds interface format
          return { firstName: signup.firstName, ...data };
        });
      })
    }).flatMap(feeds => Observable.combineLatest(feeds));

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