I've been trying to create a demo "Schedule-App" powered by Google's Firebase, but I'm facing some difficulties updating specific values of an Array with Map values on the side of Firestore.
As you can see on the following image, what we want to achieve is onButtonPress, this specific value to be updated.
I've created a Stream of data and manage it via StreamProvider.
StreamProvider<DocumentSnapshot>.value(
value: FirebaseFirestore.instance.collection('schedule').doc(FirebaseAuth.instance.currentUser.uid).snapshots(),
I'm using the following method to update Array's data, but it doesn't work.
Future<void> updateUserData(int index, String title, String text, int hour, bool check) async {
DocumentReference snapshots = FirebaseFirestore.instance.collection('schedule').doc(FirebaseAuth.instance.currentUser.uid);
snapshots.update({
['standard_schedule'][index]: {'title': title, 'text': text, 'hour': hour, 'check': check}
});
}
What changes should I make to the method above, so that the bool value to be updated, every time the button is pressed?
===============================================
SOLUTION (10/24/2020):
Firestore does not provide a way to update an array element at an index. You have to read the entire document, modify the array in memory, then write the entire array back to the document.
Firestore does not provide a way to update an array element at an index. You have to read the entire document, modify the array in memory, then write the entire array back to the document.
This is my solution.
var array=[{'title': title, 'text': text, 'hour': hour, 'check': check}];
snapshots.update({'standard_schedule': FieldValue.arrayUnion(scores)});
Related
To optimize usage, I have a Firestore collection with only one document, consisting in a single field, which is an array of strings.
This is what the data looks like in the collection. Just one document with one field, which is an array:
On the client side, the app is simply retrieving the entire status document, picking one at random, and then sending the entire array back minus the one it picked
var all = await metaRef.doc("status").get();
List tokens=all['all'];
var r=new Random();
int numar=r.nextInt(tokens.length);
var ales=tokens[numar];
tokens.removeAt(numar);
metaRef.doc("status").set({"all":tokens});
Then it tries to do some stuff with the string, which may fail or succeed. If it succeeds, then no more writing to the database, but if it fails it fetches that array again, adds the string back and pushes it:
var all = await metaRef.doc("status").get();
List tokens=all['all'];
List<String> toate=(tokens.map((element) => element as String).toList());
toate.add(ales.toString());
metaRef.doc("status").set({"all":toate});
You can use the methods associated with the Set object.
Here is an example to check that only 1 item was removed:
allow update: if checkremoveonlyoneitem()
function checkremoveonlyoneitem() {
let set = resource.data.array.toSet();
let setafter = request.resource.data.array.toSet();
return set.size() == setafter.size() + 1
&& set.intersection(setafter).size() == 1;
}
Then you can check that only one item was added. And you should also add additional checks in case the array does not exist on your doc.
If you are not sure about how the app performs the task i.e., successfully or not, then I guess it is nice idea to implement this logic in the client code. You can just make a simple conditional block which deletes the field from the document if the operation succeeds, either due to offline condition or any other issue. You can find the following sample from the following document regarding how to do it. Like this, with just one write you can delete the field which the user picks without updating the whole document.
city_ref = db.collection(u'cities').document(u'BJ')
city_ref.update({
u'capital': firestore.DELETE_FIELD
})snippets.py
I'm trying to find a way to add element to map field inside firebase database from my flutter code. The element as well is a map. So it's a nested map.
Future updateImageDate({
String token,
int rating,
int like,
int display_count,
//Map participants,
}) async {
return await pictureCollection.document(token).updateData({
'rating': rating,
'like': like,
'display_count': display_count,
//'participants': participants,
// I want to add only one element to this existing map field in firebase database.
// Although currently it's empty, I want to keep add new element every time I use this method.
// The element as well is a map. So it's a nested map.
});
}
Please help me! I'm looking forward to hearing from you. Thank you in advance. :D
To write to a map, use dot (.) notation. So:
pictureCollection.document(token).updateData({ 'path.to.field': 'new value' });
I'm quite new to Firebase Flutter. I'm developing a mobile application to share books among others.
In firebase firestore,
I have 'users' collections which contain all the user data with unique id
I have 'books' collection which contain all the book data with unique id created automatically
Also I have 'global' collection with single document with one integer field called 'bookcount'.
Users can can have many books.
Now I want to create a another unique id field for book. idea is to have simple integer id.
One way of doing this is get list of books and find the length (count) and add 1 when creating a new record. I have ruled out this method as if many users using simultaneously, I think this can lead to duplicate ids.
So I have created a another collection global with single document and field name bookcount. Which hold number of books (rough count) on books collection. So idea is each time when adding a book to a collection increase bookcount and use this value as simple unique id for a book. This bookcount may not represent actual books as user can discard the book entry before saving it, which is okay as I only need a simple unique id.
class DatabaseService {
...
...
//final CollectionReference bookCollection = Firestore.instance.collection('users');
//final CollectionReference bookCollection = Firestore.instance.collection('books');
final CollectionReference globalData = Firestore.instance.collection('global');
...
...
Future<String> bookId() async
{
String uniquebookid = await globalData.document('SomeHardcodedID').updateData(
{
'bookcount': FieldValue.increment(1)
}).then((voidvalue) async
{
String cid = await globalData.getDocuments().then((bookvalue) => bookvalue.documents.single.data['bookcount'].toString());
return cid;
});
return uniquebookid;
}//future bookId
...
...
}//class
Now this works. well somewhat, Can we do this better? In here there are two parts, first increment the value bookcount, and then retrieve it.
Can we do this in one go?
If I try to call this method consecutively really fast when returning a value it might skip few numbers. I have call this from a button and try to press as fast I could. I think counter increase but it return
same number few times. and then skip some when press again. for example 1,2,3,4,8,8,8,8,9,10,... So at counter 4 I try to press the button multiple times. I wonder how this will behave when multiple users adding multiple books at the same time.
How Can I fix this?
Please Help, Thanks.
I think the problem was since await globalData.document('SomeHardcodedID').updateData is not producing a return value (void), as soon as this fired next call also execute which is okay, which okay for most scenarios.
However if bookId called few times within very short period (milliseconds) this produce number before FieldValue.increment(1) process.
I am trying to update or add to the end of the Lists that are in a Map and all inserted into a List that contains those maps. The List name is 'classes', what I have tried doing was using dot notation, so classes.index.example, but that doesn't work. Why...let's say I have two indexes in the list, If I go ahead and update index 0, the 'questions' and 'answers' will get inserted into that correct index, But for some reason, it will delete index 1 and any other that was created. It's as if It's overwriting all the data, but I don't understand why, I am not using 'setData()' Also, if I leave 'title' out, that too will get deleted??
Future updattingUserData(int index, List<dynamic> question, List<dynamic> answer, String title) async {
return await _collref.document(uid).updateData({
"classes.$index.questions": FieldValue.arrayUnion(question),
"classes.$index.answers": FieldValue.arrayUnion(answer),
//"classes.$index.title": title
});
}
Firestore doesn't have the capability of changing an array element knowing only its index within an array field. What you will have to do is read the document, modify the classes array in memory, then update the entire classes array field back to the document.
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.