Query a Map containing an ID saved in Cloud Firestore with Dart/Flutter

Question

How to get a Map stored in Cloud Firestore with Dart/Flutter ? I tried this but it only works with Array :

Firestore.instance
            .collection(\'posts\')
          


        

Answer 1

It doesn't really make sense for userlist to be an array here. Firestore doesn't let you query for values of maps inside an array. Just store it as a map. If userlist was just a map of uid/value pairs, you could query it like this using dot notation:

Firestore.instance
        .collection('posts')
        .orderBy('createdAt', descending: true)
        .where('userlist.' + userId, isEqualTo: true)
        .snapshots(),

Answer 2

Just adding to Doug Stevenson's answer, I had to use the key isGreaterThan: '' in order to not get an empty array.

Firestore.instance
    .collection('posts')
    .where('userlist.' + userId, isGreaterThan: '')
    .snapshots(),

Answer 3

I don't recommend your way of data model. Because of some limitations as below:

1. You can only have 20000 fields in a firestore document (including array fields).
2. You can't assign security rules to each field. Security Rules is a thing that you have to think of.
3. You can't query them.

So, better I would recommend you to use documents for each user.