Get all documents from collection in firestore

Question

I'm trying to get all posts from my 'instagram' clone app. This is the path I have in firestore: posts > (unique ownerId) > userPosts > (unique postId)

How can I retrieve all posts using a stream builder? I tried doing so with

body:
StreamBuilder<QuerySnapshot>(
          stream: postsRef.snapshots(),
          builder: (context, snapshot) {
            if (!snapshot.hasData) {
              return circularProgress();
            }
            List<Post> posts = snapshot.data.documents.map((doc) =>  Post.fromDocument(doc)).toList();
            return ListView(children: posts);
          },
        )

I want to display only the posts' pictures in a stack of cards.

Answer 1

You can't use wildcards with listeners in Cloud Firestore. You need to name the specific document and collections in the path. So, if your (unique ownerId) is unknown at the time of the query, you will not be able to know anything about the documents changing in its subcollections.

As an alternative, on a backend you control, you can list subcollections of a document, then query those documents. Or, you can use a Cloud Functions trigger and notify interested client apps (maybe with Cloud Messaging) as changes happen.