Converting Firebase Querysnapshots into an Array of objects: A step-by-step guide

I am struggling to extract specific teams from a group of teams. It appears that I need to transform the snapshot into the Team object. Is there a simpler way to convert a snapshot into an array? As a beginner in firebase/angular, I may be overlooking something basic.

using angular 5.5.2

export class Team {
    internalTeamName: string;
    externalTeamName: string;
    creatorNumber: number;
    teamAdmins: TeamMember[];
    teamMembers: TeamMember[];
    constructor(code ommitted)
}

service.module

loadTeams(email){
const teamArray: Team[] = null;
this.firestore.collection('teams', ref => ref.where('teamAdmins', 'array-contains', email))
.get()
.forEach(function(childSnapshot) { 
teamArray.push(childSnapshot);})
.then(
   return teamArray )
.catch(
  err => console.log(err)
)

The error message generated by the code above: Argument of type 'QuerySnapshot' is not assignable to parameter of type 'Team'. Type 'QuerySnapshot' is missing the following properties from type 'Team': internalTeamName, externalTeamName, creatorNumber, teamAdmins, teamMembers

function calling the above function: What is the best practice when calling service functions?

public teamArray: Team[] = null;

ngOnInit() {
this.teamArray = this.teamCrudService.loadTeams(this.authService.email);
}

Answer №1

Converting a querySnapshot into an Array in Firebase 9+

In short: Consider using

querySnapshot.docs.map(doc => doc.data())

Here's an example of how it can be used:

async function fetchUsers() {
  let querySnapshot = await getDocs(collection(db, 'users'))
  return querySnapshot.docs.map(doc => doc.data())
}

querySnapshot.docs retrieves an array of documentSnapshot objects, each with a .data() method to access the actual data you need.

While the Firebase docs demonstrate using

querySnapshot.forEach(doc => {etc.})
, they don't explicitly mention the approach I've shared here.

Answer №2

.fetchData().retrieve() When called, this method does not output an array; instead, it returns a CollectionSnapshot object that contains the attribute .contents. Inside each item in the array is a DocumentSnapshot object with a feature called .info, which holds the data extracted from the document.

To learn more, make sure to check out the official documentation available at https://firebase.google.com/docs/reference/js/firebase.firestore.CollectionReference

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