javascript - switchMap 返回一项

Question

我正在尝试使用 switchMap 运算符切换可观察值:

return this.db.list(`UserPlaces/${this.authData.auth.auth.currentUser.uid}`, {
    query: {
      orderByChild: 'deleted',
      equalTo: false
    }
  })
  .map((locations:any)=>{
    console.log(JSON.stringify(locations,null,2));
    return locations.map(location=>{
      return location.$key;
    });
  }).flatMap(locations=>{
    return locations
  }).switchMap(location=>{
    console.log(location);
    return this.db.object(`Devices/${location}`)
  })
  .do(console.log);

我得到一个可观察值，而不是一组可观察值。

I need to get array of "this.db.object(Devices/${location})"

如何解决这个问题？

谢谢。

Answer 1

您可能想要forkJoin可观察量以将它们放入一次提交中。你可以这样做:

return this.db.list(`UserPlaces/${this.authData.auth.auth.currentUser.uid}`, {
    query: {
      orderByChild: 'deleted',
      equalTo: false
    }
  })
  .map((locations:any)=>{
    console.log(JSON.stringify(locations,null,2));
    return locations.map(location=>{
      return location.$key;
    });
  }).switchMap(locationKeys =>{
    console.log(location);
    const locationObs = locationKeys.map((key) => this.db.object(`Devices/${key}`);
    return Observable.forkJoin(...locationObs);
  })
  .reduce((acc, location) => [...acc, location], []);
  .do(console.log);