Question 275630 in Flutter Question posted in
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Flutter – Convert QueryDocumentSnapshot to list

I have a snapshot from firestore that I need to convert to a List list.

I have been reading about AsyncSnapshot snapshots and they come back as json, correct?

I need to convert the data in the snapshot to a list of the type "Events" for an appointment screen.

Here is the data model for Events:

String? id;
  String? eventName;
  DateTime? eventStartTime;
  String? eventDuration;
  DateTime? eventDate;
  String? eventDescription;
  String? userId;
  String? companyId;

I also have a function in my code for converting json to a map and then I type cast it as a list.

factory Events.fromJson(DocumentSnapshot doc) {
    Map data = doc.data() as Map<String, dynamic>;
    return Events(
      id: doc.id,
      eventName: data['eventName'],
      eventStartTime: (data['eventStartTime'] as Timestamp).toDate(),
      eventDuration: data['eventDuration'],
      eventDate: (data['eventDate'] as Timestamp).toDate(),
      eventDescription: data['eventDescription'],
      userId: data['userId'],
      companyId: data['companyId'],
    );
  }

This is where I am trying to execute this code:

if (snapshot.connectionState == ConnectionState.waiting) {
                return const Center(child: CircularProgressIndicator());
              } else {
                if (snapshot.hasData && snapshot.data!.docs.isNotEmpty) {
                  List<Events> eventsList =
                      Events.fromJson(snapshot.data) as List<Events>;   <<< HERE
                  return _buildTableCalendar(eventsList);
                } else {
                  return _buildTableCalendar();
                }
              }

This code is inside a StreamBuilder

I get an error when I try to execute the Events.fromJson() line. Here is the error:
enter image description here

How do I convert the snapshot to an List ?

Thanks

I made the changes suggested and now I get this error:
enter image description here

UPDATE:
I tried the code from Usama and not I get this error:
enter image description here

Tags:

2

Answers


  1. 0

    You need to iterate through snapshot.data?.docs which can return events List.

    if (snapshot.hasData && snapshot.data!.docs.isNotEmpty) {
  List<Events> eventsList =
      snapshot.data?.docs.map((e) => Events.fromJson(e)).toList() ??
          [];
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  2. 0

    First you need to get collections then you need to convert querysnapshot to your custom object list.

    Here is the code to achieve this

    QuerySnapshot<Map<String, dynamic>> querySnapshot = await
        _db.collection("your collection).get();
      if (querySnapshot.docs.isNotEmpty) {
        List<Events> events = [];
        for (var snapshot in querySnapshot.docs) {
          Events event = Events.fromJson(snapshot.data());
          events.add(event);
        }
      }
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