Pushing more data to the same document id

Question

Im pretty new to Flutter, which is why I seek some help here. I would like to push/add more exercises to the same document id in firestore. So it is stored as one workout. I have made a class called exercise, I would like to ad more under. I have included a picture of the firestore.

This is the following way I add to firestore:

final exercise = Exercise(
  date: DateTime.now(),
  name: 'Leg',
  reps: ['1', '2'],
  weight: ['50', '40']);

String id = FirebaseFirestore.instance.collection('workouts').doc().id;
FirebaseFirestore.instance
    .collection('workouts')
    .doc(id)
    .set(exercise.toFirestore());

Answer 1

With little information, if you want to add to the array, for example increase the list of reps (From ['1','2'] to this ['1','2','3'], you can do this:

String id = FirebaseFirestore.instance.collection('workouts').doc().id;
FirebaseFirestore.instance
    .collection('workouts')
    .doc(id)
    .update({'refs': Fielvalue.arrayUnion(['3'])});

But if you want to include fields to an already made document:

var db = FirebaseFirestore.instance;
final batch = db.batch();
var workout = db.collection("workouts").doc("your document");

//update
batch.update(workout, {"situps": ['1','2','3','4']});

// Commit the batch
batch.commit().then((_) {
  // done
});