Closure: () => Map<String, dynamic> from Function 'data':

Question

So im trying to stream data from firestore but when printing the data I get:

I/flutter ( 8356): Closure: () => Map<String, dynamic> from Function 'data':.

I am using this code to fetch the data:

 void messagesStream() async {
    Stream collectionStream = _firestore.collection('messages').snapshots();
    await for (var snapshot in collectionStream) {
      for (var message in snapshot.docs) {
        print(message.data());
      }
    }

When new data is added to the messages collection I get the Closure message so it is interacting with the databse.

What I want is it to print out the contents of the new document within the collection.

Any help is appreciated.

Answer 1

That's not the way you're supposed to iterate the results of a Stream. If you have a Stream and you want to process its results, you're supposed to use listen() to receive the results asynchronously.

Stream collectionStream = _firestore.collection('messages').snapshots();
collectionStream.listen((QuerySnapshot querySnapshot) {
    querySnapshot.documents.forEach((document) => print(document.data()));
}

See also: Firestore collection query as stream in flutter

You might also want to review the documentation to learn how to query Firestore in Flutter.