Convert CollectionReference in AngularFirestoreCollection or Observable?

问题

My method is returning a CollectionReference. However, this method used to return a AngularFirestoreCollection<myObj> before I converted it to Observable<myObj[]> to work with arrays.

humanCol : AngularFirestoreCollection<Human>;
humanObersArray: Observable<Human[]>;

constructor(private db: AngularFirestore) { }

Before I was using this way. Work greats to fetch all data.

buildHuman(): Observable<Human[]> {
   this.humanCol = this.db.collection('path');
   return this.humanObersArray = this.humanCol.valueChanges();
}

Now, I use have optional parameters.

buildHuman(param1: string, param2?: string, param3?: string...){ 
  this.db.collection('path', ref => {
  let retVal = ref as any;
  if (param1 != null) { retVal = retVal.where('param1', '==', param1) }
  if (param2 != null) { retVal = retVal.where('param2', '==', param2) }
  if (param3 != null) { retVal = retVal.where('param3', '==', param3) }
  ...
  return retVal; //this return a CollectionReference 
  });
}

How I can to convert retVal to AngularFirestoreCollection<T> or Observable?

回答1:

Your function buildHuman doesn't return anything. Just return the this.db.collection call and you get a AngularFirestoreCollection. Or add call valueChanges like before to get an observable:

buildHuman(param1: string, param2?: string, param3?: string): AngularFirestoreCollection<any> {
    return this.afs.collection('users', ref => {
        let retVal = ref as any;
        if (param1 != null) { retVal = retVal.where('param1', '==', param1); }
        if (param2 != null) { retVal = retVal.where('param2', '==', param2); }
        if (param3 != null) { retVal = retVal.where('param3', '==', param2); }
        return retVal;
    });
}

buildHuman(param1: string, param2?: string, param3?: string): Observable<any> {
    return this.afs.collection('users', ref => {
        let retVal = ref as any;
        if (param1 != null) { retVal = retVal.where('param1', '==', param1); }
        if (param2 != null) { retVal = retVal.where('param2', '==', param2); }
        if (param3 != null) { retVal = retVal.where('param3', '==', param2); }
        return retVal;
    })
    .valueChanges();
}

来源：https://stackoverflow.com/questions/51158991/convert-collectionreference-in-angularfirestorecollectiont-or-observable

标签

angular