CODEWITHSUNDEEP
firebasefluttergoogle-cloud-firestore
Adham Saheb
Adham Saheb

Reputation: 55

Read a document from Firestore with id inside another document

I have a collection named sessions, inside each session there is a coach id which is a document id for a user document. I'm trying to read all sessions and then for each session I want to fetch the user document, the coaches list (users) leaves the bloc empty, I figured it's an issue with asynchronous tasks.

      List<Session> sessions;
      List<MyUser> coaches;
      yield AdminsessionsLoading();
      await datasource
          .fetchMonthSessions(event.month, event.year)
          .then((data) async => {
                sessions = data,
                data.forEach((session) async => {
                      await adminDatasource
                          .fetchUser(session.coachId)
                          .then((coach) => coaches.add(coach))
                    })
              });
      //after fetching sessiosn, fetch the coaches

      print(coaches);
      print("Sessions Fetched " +
          " - Sessions : " +
          sessions.length.toString() +
          " - Coaches : " +
          coaches.length.toString());

      yield AdminsessionsLoaded(sessions: sessions, coaches: coaches);
    }

What is the correct way for me to read coaches and sessions the right way ?

Upvotes: 0

Views: 48

Answers (1)

LeadDreamer
LeadDreamer

Reputation: 3499

.forEach() has no return value, and you cannot await it - so while your code spawns multiple asynchronous tasks, it doesn't wait for any of them. You could use

await Promise.all(
               data.map((session) async => {
                      await adminDatasource
                          .fetchUser(session.coachId)
                          .then((coach) => coaches.add(coach))
                    })
              });
         );

to wait for all of them to complete ( .map() will return an array of promises). This is a HUGE limitation of .forEach() in asynchronous code.

Upvotes: 1

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