In a pretty complex sheet, I am using FutureBuilder and Listview.builder which help me to list all groups around me (using Algolia search), which looks as follows:
future = _algolia
.index('groups')
.setAroundLatLng(
'${_startLocation.latitude.toString()}, ${_startLocation.longitude.toString()}')
.setFacetFilter("category:$category")
.search(_query)
.setHitsPerPage(1000)
.getObjects();
Now, I also want to include the totalUsers for each group. Problem: they are saved in Firestore (groups/groupId/totalUsers). Now for Firestore when I need to request the totalUsers, I have to hand over every groupId (which comes async from Algolia and is simply available in FutureBuilder as document.data['groupId']). So I tried to call totalUsers from a ListTile within FutureBuilder, with getTotalUsers(document.data['groupId']), and
getTotalUsers(groupId) async{
DocumentReference reference =
Firestore.instance.collection('groups').document(groupId.toString());
DocumentSnapshot snapshot;
snapshot = await reference.get();
return snapshot['totalUsers'];
}
...but since it is async, it just gives me 'Instance of a Future'. Now what's the easiest way to include totalUsers and 'await' it from the widget tree? I think I cannot load it in initstate, since I first have to hand over the specific userIds from the groups 'aroundme'.
Related
Since transaction only accepts DocumentReference so I couldn't handle the .where().
DocumentReference test1= FirebaseFirestore.instance.collection("users").doc(currentUser.uid);
Query<Map<String, dynamic>> test2= FirebaseFirestore.instance.collection("users").where('test',isEqualTo: 'mytest').limit(1);
return FirebaseFirestore.instance.runTransaction((transaction) async {
//no problem with this DocumentSnapshot
DocumentSnapshot _value = await transaction.get(test1);
//BUT
//here in test2 will never accept Query<Map<String, dynamic>>
//since the transaction is only accept DocumentReference
DocumentSnapshot _value2 = await transaction.get(test2);
if (_value.exists) {
//action
}
})
How can I get the .whereReference into the transaction?
Cloud Firestore doesn't provide a solution in which you can use transactions on documents that are obtained through queries. Please also note that a Transaction object cannot perform a query. The single option that you have is to use transactions on a single individual document.
According to your last comment, since you are using a .limit(1) it means that you need to update a single document, a case in which you can create a reference that points exactly to that document and perform the transaction:
DocumentReference uidRef = FirebaseFirestore.instance.collection("users").doc(currentUser.uid);
uidRef.runTransaction(/* ... /*);
If you don't know the UID of the user on which you need to perform the transaction, then you should perform the necessary query outside the transaction, get the ID of the document, and perform the transaction right after that. But as you can see, there is no way you can do these two operations in a single go.
Please also remember, that a transaction makes sense to be used only if you need to read some data from a document in order to make a decision before you update it. I'm not 100% sure, but in your particular case, I don't think you do that. You are not using the value of _value in a way you decide what to do with it. If this is your scenario, a batch write will definitely do the job.
In my firestore I have a list of documents which represent locations on a map.
I would like to show a local notification not only when a new document is created in the database, but also when the location is within a certain distance from my current location.
At the moment I have a streambuilder which loads the position into my local map, and a streamlistener to give a notification on a new document:
CollectionReference loc =
FirebaseFirestore.instance.collection('locations');
late Stream<QuerySnapshot> _locStream;
late StreamSubscription<QuerySnapshot> streamSub;
#override
void initState() {
super.initState();
_locStream = loc.snapshots();
streamSub = _locStream.listen((data) {
final snackBar = SnackBar(
content:
Text('New location added!'));
ScaffoldMessenger.of(context).showSnackBar(snackBar);
});
}
the problem is that the stream is returning ALL the documents, not only the new one, so I have no idea how to "isolate" the new one and, more important, how to get its value in order to compare it with my current location.
Is that possible to achieve so?
A Firestore QuerySnapshot always contains all information that fits within the query. But when the QuerySnapshot is an update on an existing listener/stream, it also contains metadata about what changes compared to the previous QuerySnapshot on the listener/stream.
To get access to this metadata, use the QuerySnapshot's docChanges property, rather than docs, and check the DocumentChangeType of the type property of each change to find only the documents that were added. In the initial snapshot that will be all of the documents, since all of them are new to the snapshot at that point.
See the Firebase documentation on viewing changes between snapshots
I'm building a Self-learning app with differente questions types. Right now, one of the questions have a field containing a list of DocumentReferences:
In Flutter, I have the following code:
Query<Map<String, dynamic>> questionsRef = firestore
.collection('questions')
.where('lesson_id', isEqualTo: lessonId);
await questionsRef.get().then((snapshot) {
snapshot.docs.forEach((document) {
var questionTemp;
switch (document.data()['question_type']) {
....
case 'cards':
questionTemp = CardsQuestionModel.fromJson(document.data());
break;
....
}
questionTemp.id = document.id;
questions.add(questionTemp);
});
});
Now, with "questionTemp" I can access all the fields (lesson_id,options,question_type, etc..), but when it comes to the "cards" field, how Can I access the data from that document reference?
Is there a way to tell firestore.instance to get the data from those references automatically? Or do I need to make a new call for each one? and, if so, how can I do that?
Thank you for your support in advance!
Is there a way to tell firestore.instance to get the data from those
references automatically? Or do I need to make a new call for each
one?
No there isn't any way to get these documents automatically. You need to build, for each array element, the corresponding DocumentReference and fetch the document.
To build the reference, use the doc() method
DocumentReference docRef = FirebaseFirestore.instance.doc("cards/WzU...");
and then use the get() method on this DocumentReference.
docRef
.get()
.then((DocumentSnapshot documentSnapshot) {
if (documentSnapshot.exists) {
print('Document exists on the database');
}
});
Concretely, you can loop over the cards Array and pass all the Futures returned by the get() method to the wait() method which "waits for multiple futures to complete and collects their results". See this SO answer for more details and also note that "the value of the returned future will be a list of all the values that were produced in the order that the futures are provided by iterating futures."
please how can I get all the value of my IndividualTaxData subcollection in Flutter.
First, you must get the reference to the parent document:
DocumentReference parentRef = Firestore.intances.collection('TaxData').document(taxDataId);
You can do the previous part with a direct reference to the document (like the code above) or with a query. Later, you must get the reference of the subcollection and the document that you get the information:
DocumentReference subRef = parentRef.collection('IndividualTaxData').document(individualTaxId);
And finally, get the data:
DocumentSnapshot docSnap = await subRef.get();
For you to return a simple document, you can use the following code for it.
var document = await Firestore.instance.collection('IndividualTaxData').document('<document_name>');
document.get() => then(function(document) {
print(document('character'));
// you can print other fields from your document
}
With the above code, you will reference your collection IndividualTaxData and then load it's data to a variable that you can print the values.
In case you want to retrieve all the documents from your collection, you can start using the below code.
final QuerySnapshot result = await Firestore.instance.collection('IndividualTaxData').getDocuments();
final List<DocumentSnapshot> documents = result.documents;
documents.forEach((data) => print(data));
// This print is just an example of it.
With this, you will load all your documents into a list that you iterate and print after - or that you can use with another method.
In addition to that, as future references, I would recommend you to check the following links as well.
Query a single document from Firestore in Flutter (cloud_firestore Plugin)
How to use Cloud Firestore with Flutter
Le me know if the information helped you!
Is there a way to fetch document after documentID like
private fun fetchCollectoionnAfterDocumentID(limit :Long){
val db = FirebaseFirestore.getInstance()
var query:Query = db.collection("questionCollection")
.startAfter("cDxXGLHlP56xnAp4RmE5") //
.orderBy("questionID", Query.Direction.DESCENDING)
.limit(limit)
query.get().addOnSuccessListener {
var questions = it.toObjects(QuestionBO::class.java)
questions.size
}
}
I want to fetch sorted questions after a given Document ID. I know I can do it using DocumentSnapShot. In order to fetch the second time or after the app is resume I have to save this DocumentSnapshot in Preference.
Can It be possible to fetch after document ID?
startAfter - > cDxXGLHlP56xnAp4RmE5
Edit
I know I can do it using lastVisible DocumentSnapshot . But I have to save lastVisible DocumentSnapshot in sharedPreference.
When app launch first time 10 question are fetched from questionCollection. Next time 10 more question have to be fetched after those lastVisible. So for fetching next 10 I have to save DocumentSnapshot object in sharedPreference. Suggest me a better approach after seeing my database structure.
And one more thing questionID is same as Document reference ID.
There is no way you can pass only the document id to the startAfter() method and simply start from that particular id, you should pass a DocumentSnapshots object, as explained in the official documentation regarding Firestore pagination:
Use the last document in a batch as the start of a cursor for the next batch.
first.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
#Override
public void onSuccess(QuerySnapshot documentSnapshots) {
=// Get the last visible document
DocumentSnapshot lastVisible = documentSnapshots.getDocuments()
.get(documentSnapshots.size() -1);
// Construct a new query starting at this document,
Query next = db.collection("cities")
.orderBy("population")
.startAfter(lastVisible) //Pass the DocumentSnapshot object
.limit(25);
// Use the query for pagination
}
});
See, here the lastVisible is a DocumentSnapshot object which represents the last visible object. You cannot pass only a document id. For more information, you can check my answer from the following post:
How to paginate Firestore with Android?
It's in Java but I'm confident you can understand it and write it in Kotlin.
Edit:
Please consider defining an order of your results so that all your pages of data can exist in a predictable way. So you need to either specify a startAt()/startAfter() value to indicate where in the ordering to begin receiving ordered documents or use a DocumentSnapshot to indicate the next document to receive, as explained above.
Another solution might be to put the document id into the document itself (as a value of a property) and order on it, or you can use FieldPath.documentId() to order by the id without having to add one.
You can also check this and this out.
There is one way to let startAfter(documentID) works.
Making one more document "get", then using the result as startAfter input.
val db = FirebaseFirestore.getInstance()
// I use javascript await / async here
val afterDoc = await db.collection("questionCollection").doc("cDxXGLHlP56xnAp4RmE5").get();
var query:Query = db.collection("questionCollection")
.startAfter(afterDoc)
.orderBy("questionID", Query.Direction.DESCENDING)
.limit(limit)
A simple way to think of this: if you order on questionID you'll need to know at least the value of questionID of the document to start after. You'll often also want to know the key, to disambiguate between documents with the same values. But since it sounds like your questionID values are unique within this collection, that might not be needed here.
But just knowing the key isn't enough, as that would require Firestore to scan its entire index to find that document. Such an index scan would break the performance guarantees of Firestore, which is why it requires you to give you the information it needs to perform a direct lookup in the index.