I have two queries for Firebase. One that returns a list of posts ("PostsModel") and one that returns a list of liked posts for a particular user ("LikedPostsModel"). I want to set an attribute called "liked" within "PostsModel" to true if it's also in the liked posts streams.
Pseudo Code:
/* Returns PostsModel, ex. [PostsModel(id: 1, liked: false), PostsModel(id: 2, liked: false), PostsModel(id: 3, liked: false), ...] */
Stream<List<PostsModel>> getListOfPosts();
/* Returns LikedPostsModel, ex. [LikedPostsModel(postsmodel_id: 2), ...] */
Stream<List<LikedPostsModel>> getListOfLikedPosts();
/* Returns combining PostsModel and LikedPostsModel, ex. [PostsModel(id: 1, liked: false), PostsModel(id: 2, liked: true), PostsModel(id: 3, liked: false), ...] */
Stream<List<LikedPostsModel>> getCombinedPosts() {
var listOfPosts = getListOfPosts();
var listOfLikedPosts = getListOfLikedPosts();
if PostsModel.id within listOfPosts is matches LikedPostsModel.postsmodel_id within listOfLikedPosts, then set PostsModel.liked = true;
return Stream<List<PostsModel>> with some fields "liked" set to true;
}
Actual Code:
My query to retrieve all posts:
Stream<List<PostsModel>> getListOfPostsStream() {
return _firestore
.collection("posts")
.snapshots()
.map((QuerySnapshot<Map<String, dynamic>> query) {
List<PostModel> postsModelList = [];
query.docs.forEach((element) {
postsModelList.add(PostsModel.fromDocumentSnapshot(element));
});
return postsModelList;
});
}
My query to retrieve liked posts:
#override
Stream<List<LikedPostsModel>> getLikedPostsByUser(User user) {
return _firestore
.collection("users")
.doc(user.id)
.collection("liked_posts")
.snapshots()
.map((QuerySnapshot<Map<String, dynamic>> query) {
List<LikedPostsModel> likedModelList = [];
query.docs.forEach((element) {
likedModelList.add(LikedPostsModel.fromDocumentSnapshot(element));
});
return likedModelList;
});
}
PostsModel
class PostsModel {
late String id;
late String bodyText;
bool liked = false;
PostsModel(
this.id,
this.bodyText,
);
...
}
LikedPostsModel
class LikedPostsModel {
late String id;
late String postsmodel_id;
bool liked;
LikedPostsModel(
this.id,
this.postsmodel_id,
this.liked
);
...
}
Any help is appreciated. Thanks!
To achieve it you should use the combineLatest2 method of the RxDart package.
I used it when developing a chat project. You know, at the conversations page of WhatsApp lists all chats and shows us the talker and the last message, message time, and seen information. My problem was my talker detail values and chat metadatas were in separate collections and I had to show the profile image and name of a talker and the last message, last message time and isSeen of the chat at the same time.
Here is an example from my chat project;
Stream<List<Chats>> getChats() {
final _userId = FirebaseAuth.instance.currentUser?.uid;
return _firestore
.collection('Chats')
.where('members', arrayContains: _userId)
.orderBy("lastMessageDate", descending: true)
.snapshots()
.map((convert) {
return convert.docs.map((f) {
String? talkerId;
var members = f.data()['members'];
if (members.length == 2) {
talkerId = members[0] != _userId ? members[0] : members[1];
}
Stream<ChatMetadata> chatStream = Stream.value(f).map<ChatMetadata>(
(document) => ChatMetadata.fromMap(
f.reference.path,
document.data(),
),
);
Stream<Talker> talkerStream = _firestore
.collection("Users")
.where('uid', isEqualTo: talkerId)
.snapshots()
.map<Talker>(
(querySnapshot) => querySnapshot.docs
.map((e) => Talker.fromMap(
e.data(),
))
.first,
);
return Rx.combineLatest2(
chatStream,
talkerStream,
(ChatMetadata chatMetadata, Talker talker) =>
Chats.combine(chatMetadata, talker),
);
});
}).switchMap((observables) {
return observables.isNotEmpty
? rx.Rx.combineLatestList(observables)
: Stream.value([]);
});
}
As you can see the getChats() method returns a Stream<List<Chats>>. The Chats model is a class that combines two other classes like ChatMetadata and Talker. Here is my Chats model;
import '/model/talker.dart';
import '/model/chat_metadata.dart';
class Chats {
String? docId;
String? talkerId;
String? talkerUsername;
String? talkerUnvan;
String? talkerProfileImage;
String? lastMessage;
DateTime? dateTime;
String? lastMessageOwner;
bool? isSeen;
List? members;
Chats({
this.docId,
this.talkerId,
this.talkerUsername,
this.talkerUnvan,
this.isSeen,
this.talkerProfileImage,
this.lastMessage,
this.dateTime,
this.lastMessageOwner,
this.members,
});
factory Chats.combine(ChatMetadata chat, Talker talker) {
return Chats(
docId: chat.docId,
talkerId: talker.id,
talkerUsername: talker.username,
talkerUnvan: talker.unvan,
isSeen: chat.isSeen,
talkerProfileImage: talker.photoUrl,
lastMessage: chat.lastMessage,
dateTime: chat.lastMessageDate,
lastMessageOwner: chat.lastMessageOwner,
members: chat.members,
);
}
}
You have to pay attention to the Rx.combineLatest2 method and switchMap method at the end of the code.
You can research all of them but in summary, the combineLatest2() merges the given Streams into a single Stream sequence by using the [combiner] function whenever any of the stream sequences emits an item. Then switchMap() converts each emitted item into a Stream using the given mapper function. Because the getChats() method has to returns the Stream<List<Chats>>.
You can store your likes in a Map rather than a List.
Stream<Map<String, bool>> getLikedPostsByUser(User user) {
return _firestore
.collection("users")
.doc(user.id)
.collection("liked_posts")
.snapshots()
.map((QuerySnapshot<Map<String, dynamic>> query) {
final likedPostsMap = HashMap<String, bool>();
query.docs.forEach((element) {
final model = LikedPostsModel.fromDocumentSnapshot(element);
likedPostsMap[model.postmodel_id] = model.liked;
});
return likedPostsMap;
});
}
Then use the resulting Map for a constant time lookup when populating your list of posts.
Stream<List<PostsModel>> getListOfPostsStream(Map<String, bool> likedPosts) {
return _firestore
.collection("posts")
.snapshots()
.map((QuerySnapshot<Map<String, dynamic>> query) {
List<PostModel> postsModelList = [];
query.docs.forEach((element) {
final model = PostsModel.fromDocumentSnapshot(element);
model.liked = likedPosts[model.id] ?? false;
postsModelList.add(model);
});
return postsModelList;
});
}
To improve performance, likes can be persisted locally so they don't have to be fetched each time your app is opened. Add a timestamp to your likes document to limit your query to changes since the last time you fetched.
I was trying to fetch from two different collection but I got a weird situation. First, I want to fetch a userID from posts collection. Then with that userID, I want to fetch data from users collection.
So, when I fetch from only the posts collection, print command works perfectly fine and prints the userID.
But when I add the users fetch statement that I showed in the code below it doesn't fetch it and shows an empty string (''), and users collection sends an error because I couldn't search the userID. What am I missing here?
class _ProductDetail extends State<ProductDetail> {
String getTitle = '';
String getLocation = '';
String getPrice = '';
String getImage = '';
String getUniversity = '';
String getProfileImage = '';
String getUserName = '';
String getSellerUserID = '';
#override
Widget build(BuildContext context) {
FirebaseFirestore.instance
.collection('posts')
.doc(widget.postID)
.get()
.then((incomingData) {
setState(() {
getTitle = incomingData.data()!['title'];
getPrice = incomingData.data()!['price'];
getImage = incomingData.data()!['postImage'];
});
});
FirebaseFirestore.instance
.collection('posts')
.doc(widget.postID)
.get()
.then((incomingData) {
setState(() {
getSellerUserID = incomingData.data()!['userID'];
});
});
print(getSellerUserID); //statement that will print the userID
//////////////////////IF I DELETE THIS SECTION, IT PRINTS THE USER ID//////////////////
FirebaseFirestore.instance
.collection('users')
.doc(getSellerUserID)
.get()
.then((incomingData) {
setState(() {
getUserName = incomingData.data()!['username'];
getProfileImage = incomingData.data()!['profileImage'];
getUniversity = incomingData.data()!['university'];
getLocation = incomingData.data()!['location'];
});
});
///////////////////////////////////////////////////////////////////////////////////////////////
return Scaffold(
....... rest of the code
Since data is loaded from Firestore asynchronously, the code inside your then blocks is called (way) later then the line after the call to get().
To see this most easily, add some logging like this:
print("Before calling Firestore")
FirebaseFirestore.instance
.collection('posts')
.doc(widget.postID)
.get()
.then((incomingData) {
print("Got data")
});
print("After calling Firestore")
If you run this code, it'll print:
Before calling Firestore
After calling Firestore
Got data
This is probably not the order you expected, but does explain why your next load from the database doesn't work: the getSellerUserID = incomingData.data()!['userID'] line hasn't been run yet by that time.
For this reason: any code that needs the data from Firestore, needs to be inside the then (or onSnapshot) handler, be called from there, or be otherwise synchronized.
So the simplest fix is to move the next database call into the `then:
FirebaseFirestore.instance
.collection('posts')
.doc(widget.postID)
.get()
.then((incomingData) {
var sellerUserID = incomingData.data()!['userID'];
setState(() {
getSellerUserID = sellerUserID;
});
print(sellerUserID);
FirebaseFirestore.instance
.collection('users')
.doc(sellerUserID)
.get()
.then((incomingData) {
setState(() {
getUserName = incomingData.data()!['username'];
getProfileImage = incomingData.data()!['profileImage'];
getUniversity = incomingData.data()!['university'];
getLocation = incomingData.data()!['location'];
});
});
});
All!
I want to delete the task by using a Dismissible widget.
I try the following
onDismissed: (direction) {
DatabaseHelper.instance.deleteTask(task.id);
_updateTaskList();
},
and it works but the animation looks wrong as if the dismissed child reappear for a second and then disappears.
I think what is happening is that the deleteTask has a delay and the _updateTaskList it's running almost at the same time.
this are my methods:
Future<int> deleteTask(int id) async {
Database db = await this.db;
final int result = await db.delete(
tasksTable,
where: '$colId = ?',
whereArgs: [id],
);
return result;
}
}
_updateTaskList() {
setState(() {
_taskList = DatabaseHelper.instance.getTaskList();
});
}
Future<List<Task>> getTaskList() async {
final List<Map<String, dynamic>> taskMapList = await getTaskMapList();
final List<Task> taskList = [];
taskMapList.forEach((taskMap) {
taskList.add(Task.fromMap(taskMap));
});
return taskList;
}
While using flutter I am able to successfully get the UserId, however I want to be able get more user data (using the UserId)
Surrounding Information:
With the userId how would I go about printing the users; name bio, membership... etc?
Since you are using Realtime Database, then to get the other data, you can do the following:
db = FirebaseDatabase.instance.reference().child("Users");
db.once().then((DataSnapshot snapshot){
Map<dynamic, dynamic> values = snapshot.value;
values.forEach((key,values) {
print(values);
print(values["name"]);
});
});
First add a reference to node Users then use the forEach method to iterate inside the retrieved Map and retrieve the other values.
Try like this :
Future<dynamic> getWeightinKeg() async {
final DocumentReference document = Firestore.instance.collection('you_collection_name').document(user_id);
await document.get().then<dynamic>(( DocumentSnapshot snapshot) async {
final dynamic data = snapshot.data;
print(data['name'].toString())
//Do whatever you want to do with data here.
});
}
getUsers() async {
//here fbPath is reference to your users path
fbPath.once().then((user){
if(user.value !=null){
Map.from(user.value).forEach((k,v){
//here users is List<Map>
setState((){
users.add(v);
});
}
}
});
}
//Or
getUsers() async {
//here fbPath is reference to your users path
//and userListener is StreamSubscription
userListener = fbPath.onChildAdded.listen((user){
//here users is List<Map>
setState((){
users.add(Map.from(user.snapshot.value));
});
});
}
//and cancel in dispose method by calling
userListener.cancel();
Im trying to return the length of a list of documents with this function:
Future totalLikes(postID) async {
var respectsQuery = Firestore.instance
.collection('respects')
.where('postID', isEqualTo: postID);
respectsQuery.getDocuments().then((data) {
var totalEquals = data.documents.length;
return totalEquals;
});
}
I'm initialize this in the void init state (with another function call:
void initState() {
totalLikes(postID).then((result) {
setState(() {
_totalRespects = result;
});
});
}
However, when this runs, it initially returns a null value since it doesn't have time to to fully complete. I have tried to out an "await" before the Firestore call within the Future function but get the compile error of "Await only futures."
Can anyone help me understand how I can wait for this function to fully return a non-null value before setting the state of "_totalRespsects"?
Thanks!
I think you're looking for this:
Future totalLikes(postID) async {
var respectsQuery = Firestore.instance
.collection('respects')
.where('postID', isEqualTo: postID);
var querySnapshot = await respectsQuery.getDocuments();
var totalEquals = querySnapshot.documents.length;
return totalEquals;
}
Note that this loads all documents, just to determine the number of documents, which is incredibly wasteful (especially as you get more documents). Consider keeping a document where you maintain the count as a field, so that you only have to read a single document to get the count. See aggregation queries and distributed counters in the Firestore documentation.
Perfect code for your problem:
int? total;
getLength() async {
var getDocuments = await DatabaseHelper.registerUserCollection
.where("register", isEqualTo: "yes")
.get();
setState(() {
total = getDocuments.docs.length;
});
}
#override
void initState() {
super.initState();
getLength();
if (kDebugMode) {
print(total);
}
}