Ionic 5 Firebase Realtime - 列表中的收藏夹

Question

我有一个带有摩托车列表的 Ionic 5 应用程序。这样，用户可以使用切换星形图标来收藏它们。然后，我在包含摩托车数据的用户节点中创建一个寄存器，如下所示：

问题是当摩托车之前被当前用户标记为“收藏”时，我无法在列表中显示“星号”图标（总是显示“star-outline”），尽管我可以从 Firebase 获取这些数据。

到目前为止我已经尝试过这种方式，但没有成功（星形图标在所有项目中保持“star-outline”）：

list.page.html

<ion-col size="6" *ngFor="let item of motos; let i = index;">
  <ion-card>
    <ion-card-header>
      <ion-fab vertical="top" horizontal="start">
        <ion-fab-button (click)="addToFavorites(item, i)" icon-only color="clear">
          <ion-icon [name]="item.favourited ? 'star' : 'star-outline'"></ion-icon>
        </ion-fab-button>
      </ion-fab>
    </ion-card-header>
    <ion-card-content>
        <div>{{item.fabricante}} {{item.nome}}</div>
        <div>{{item.ano_model}}</div>
    </ion-card-content>
  </ion-card>
</ion-col>

list.page.ts

import { CrudMethodsService } from './services/crud-methods.service';

basePath = 'motos';
basePathU = 'users';

constructor(private crudServices: CrudMethodsService, public afAuth: AngularFireAuth) {      
 this.crudServices.getMotos(this.basePath).subscribe(res => {
    this.motos = res;
    this.afAuth.authState.subscribe(user => {
      if (user){
        this.userId = user.uid;
        const favoritas = 'favoritas';
        this.crudServices.getFavorites(this.basePathU, this.userId, favoritas).subscribe(us => {
          this.isFavorite = us;
          this.isFavorite.forEach(resp => {
            const item = this.motos;
            const p = this.favorites.indexOf(item);
            item.favourited = item.favourited ? false : true;
            for (let j = 0; j < this.motos.length; j++) {
              if (resp.item.key === this.motos[j].key && p === -1) {
                this.favorites.push(item);
                item.favourited = true;
              }
            }
          });
        });
      }
    });
  });
}

crud-methods.service.ts

getMotos(basePath: string) {
  return this.db.list(basePath).snapshotChanges().pipe(map(changes => {
    return changes.map(c => {
      const data = c.payload.val();
      const id = c.payload.key;
      return { key: id, ...(data as object) };
    });
  }));
}

getFavorites(basePath: string, key: string, path: string) {
  return this.db.list(basePath + '/' + key + '/' + path).snapshotChanges().pipe(map(changes => {
    return changes.map(c => {
      const data = c.payload.val();
      const id = c.payload.key;
      return { key: id, ...(data as object) };
    });
  }));
}

Answer 1

您可以使用 rxjs 运算符 switchmap 来实现您的合并行为。 switchmap 允许您使用一个 Observable 的结果，但用另一个 Observable 响应。因此，您可以像以前一样在没有嵌套订阅的情况下链接可观察对象（这通常会导致问题）。这在您的构造函数中看起来像这样：

this.motosWithFavoritesObservable = this.afAuth.authState.pipe(
  map(user => user.uid),
  switchMap(userid => {
    return this.crudServices.getFavorites(this.basePathU, userid, 'favoritas');
  }),
  switchMap((favorites: { key: string }[]) => {
    return this.crudServices.getMotos(this.basePath).pipe(
      map((motos: { key: string, favourited: boolean }[]) => {
        favorites.forEach(fav => {
          const index = motos.findIndex(moto => moto.key === fav.key)
          if (index !== -1) { // if the moto corresponding to the fav is found in the list
            motos[index].favourited = true;
          }
        })
      })
    )
  })
);

motosWithFavoritesObservable.subscribe(motos => this.motos = motos);

Ionic 5 Firebase Realtime - 列表中的收藏夹

Ionic 5 Firebase Realtime - Favorites in a list

javascript

firebase-realtime-database

ionic4

angularfire2