How do update array values in Flutter cloud_firestore?

Question

I have a document with an array field in it.

How can I update the array?

In firebase functions, with typescript, I did something like this:

admin.firestore()
    .collection('friendships')
    .doc(caller.data["uid"])
    .update({
        friends: admin.firestore.FieldValue
            .arrayUnion({
                          friendDisplayName: snapshot.data["friendDisplayName"],
                          friendUid: snapshot.ref
                       })
    })

I cannot find any alternative with Flutter.. how can I do?

this didn't work - Firestore.instance.collection('friendships').document(caller.data["uid"]).updateData({ 'friends':{ 'friendDisplayName': snapshot.data["friendDisplayName"], 'friendUid': snapshot.ref } ? — anmol.majhail
– anmol.majhail, Commented Oct 12, 2018 at 6:25

Harish · Accepted Answer · 2019-01-24 18:22:15Z

5

Something like this

firestore.instance.
    .collection('friendships')
    .document(caller.data["uid"])
    .updateData({
  friends: FieldValue.arrayUnion({
    friendDisplayName: snapshot.data["friendDisplayName"],
    friendUid: snapshot.ref
  })
});

answered Jan 24, 2019 at 18:22

Harish

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1 Comment

user13133459 Over a year ago

what does caller.data retrieve? I'm new to dart and i'm struggling to update array in my Firebase

Shi · Accepted Answer · 2020-02-09 22:58:10Z

4

The solution I give you is when you use Transactions, but regardless of that, it works the same...

List<dynamic> list = List.from(documentSnapshot.data['uids']);
list.add(uid);
await documentTransaction.update(
  postRef,
  <String, dynamic>{
    'counter': documentSnapshot.data['counter'] + 1,
    'uids': list,
  },
);

edited Feb 9, 2020 at 22:58

Shi

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answered Jan 24, 2019 at 19:25

Luis Meneses

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1 Comment

Panagiss Over a year ago

The thing is that some times you don't have the ability to fetch the whole list and then add a new element. It would be nice if you could just add a new element to the existing array without fetching first

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