Having issues trying to get array data out of my collection - firebase

Question

I am trying to retrieve all the uid's who liked a comment, to display the list of people on the page. I am having issue querying this data using StreamBuilder. I've tried it so many different ways that I've seen on here but I'm not having any luck. I got different errors or no data at all before this. Can anyone help me out with this issue?
This is the database path
/comments/411f47a0-8404-4800-a32e-35c260d7b670/comments/3ygnNwXM3WQlmoNDV6Ac
So comments/postId/comments/ then the comment data is here with the array of "likers" containing each uid
Right now, I'm getting this error. And it's pointing the the return StreamBuilder line.
type 'QuerySnapshot' is not a subtype of type 'DocumentSnapshot'
This is the widget that I have the StreamBuilder in.
#override
Widget build(BuildContext context) {
return StreamBuilder(
stream: Firestore.instance
.collection("comments")
.document(widget.postId)
.collection("comments")
.where("likers", arrayContains: widget.uid)
.snapshots(),
builder: (context, snapshot) {
if (snapshot.hasData) {
var user = User.fromDocument(snapshot.data);
return Padding(
padding: const EdgeInsets.only(top: 5.0, left: 5.0, right: 5.0),
child: ClipRRect(
borderRadius: BorderRadius.circular(15.0),
child: Card(
child: ListTile(
tileColor: R.colors.grey200,
leading: user.photoUrl.isNotEmpty
? CachedNetworkImage(
placeholder: (context, url) => CircleAvatar(
backgroundColor: R.colors.grey,
radius: 25.0,
),
imageUrl: user.photoUrl,
width: 50.0,
height: 50.0,
fit: BoxFit.cover,
)
: Icon(
Icons.account_circle,
size: 50.0,
color: R.colors.grey,
),
title: Text(
(user.username),
style: TextStyle(
color: R.colors.black, fontWeight: FontWeight.bold),
),
subtitle: Text(
(user.profileName),
style: TextStyle(color: R.colors.black),
),
trailing: FlatButton(
color: R.colors.blueAccent,
shape: RoundedRectangleBorder(
borderRadius:
BorderRadius.all(Radius.circular(25.0))),
clipBehavior: Clip.hardEdge,
onPressed: () {
if (!following) {
controlFollowUser();
} else {
controlUnfollowUser();
}
},
child: Text(following
//currentUser.following.contains(user.id)
? "Unfollow"
: "Follow")),
),
),
),
);
} else {
return ListTile(
title: Text("Nothing here"),
);
}
});
}
This line is getting the user data like the username, and profile picture and it's able to get that because it would have the correct uid's from the comment data that was queried. Here is where it originates from.
var user = User.fromDocument(snapshot.data);
factory User.fromDocument(DocumentSnapshot doc) {
if (doc != null) {
return User(
following: doc['following']?.cast<String>() ?? [],
followers: doc['followers']?.cast<String>() ?? [],
id: doc.documentID,
email: doc['email'] ?? "",
username: doc['username'],
photoUrl: doc['photoUrl'],
url: doc['photoUrl'],
profileName: doc['profileName'],
bio: doc['bio'],
createdAt: doc['createdAt'],
talkingTo: doc['talkingTo'],
receiverName: doc['receiverName'],
);
} else {
return new User();
}
}
Any help would be appreciated.

Answer 1

The error message is telling you that snapshot.data returns a QuerySnapshot object, but you're trying to pass it to a function that takes a DocumentSnapshot as a parameter. They're not compatible. A QuerySnapshot represent the results of a query that could return zero or more documents. A DocumentSnapshot represents a single document.
If you want to process the results of this query, you will have to iterate the documents in the QuerySnapshot and deal with them individually. There is an example in the documentation:
querySnapshot.docs.forEach((doc) {
print(doc["first_name"]);
});
If your query could return multiple user documents You're going to have to iterate the results and decide what to do with each document. If you want to pass each DocumentSnapshot to User.fromDocument(), that would compile (but I don't know if it would do what you want, since we can't see the data from your query).