Flutter Firestore - How To Read And Write Arrays of Objects

Question

So I've been struggling with reading and writing arrays of objects in Firestore using Flutter. For writing, the array never gets updated in Firestore and I don't know why. I've tried:

.updateData({"tasks": FieldValue.arrayUnion(taskList.tasks)});

and

.updateData(taskList.toMap());

but neither seem to do anything.

For reading, I usually get the error type 'List<dynamic>' is not a subtype of type 'List<Task>'. I'm pretty sure it has something to do with my class structure but I can't figure it out. I've tried many different ways to get the data as a List of Tasks but all attempts have failed. Here is my current broken code:

TaskList.dart

class TaskList {
  String name;
  List<Task> tasks;

  TaskList(this.name, this.tasks);

  Map<String, dynamic> toMap() => {'name': name, 'tasks': tasks};

  TaskList.fromSnapshot(DocumentSnapshot snapshot)
      : name = snapshot['name'],
        tasks = snapshot['tasks'].map((item) {
          return Task.fromMap(item);
        }).toList();

}

Task.dart

class Task {
  String task;
  bool checked;

  Task(this.task, this.checked);

  Map<String, dynamic> toMap() => {
        'task': task,
        'checked': checked,
      };

  Task.fromMap(Map<dynamic, dynamic> map)
      : task = map['task'],
        checked = map['checked'];
}

Any help or advice is appreciated!

have a look at this answer please stackoverflow.com/a/53149420/2863386 — Shyju M
– Shyju M, Commented Jan 3, 2019 at 6:24

Jared · Accepted Answer · 2019-01-03 05:51:34Z

9

I ended up making the tasks list of type dynamic and that solved most of my reading problems. Still don't understand why though.

List<Task> tasks;

And for writing, I just changed the fromMap() to toMap() for initializing the tasks.

'tasks': tasks.map((item) {
      return item.toMap();
    }).toList(),

answered Jan 3, 2019 at 5:51

Jared

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1 Comment

Matthew Rideout Over a year ago

Similar documentation from Flutter here: flutter.dev/docs/development/data-and-backend/…

marc_s · Accepted Answer · 2022-03-01 20:28:45Z

0

Get an array from firebase you can use query snapshot to get arraylist

QuerySnapshot querySnapshot =
            await FirebaseFirestore.instance.collection('EnglishQuotes').get();
// for a specific field
final allData =  querySnapshot.docs.map((doc) => doc.get('item_text_')).toList();
print("length = ${allData.length}");
print("all data = ${allData}");

edited Mar 1, 2022 at 20:28

marc_s

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answered Feb 28, 2022 at 12:44

Rishita Joshi

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