I am trying to retrieve data of all the users of the users collection and compare it with some other data. I am able to retrieve data of a particular user from its uid but want to iterate through all the collections and documents.
If you don't specify a specific document ID and use the get() method on a CollectionReference, it'll return a QuerySnapshot (containing all documents in that collection) which essentially is an array of QueryDocumentSnapshot.
FirebaseFirestore.instance
.collection('users')
.get()
.then((QuerySnapshot querySnapshot) {
querySnapshot.docs.forEach((doc) {
print(doc["field_name"]);
});
});
You can use "QuerySnapshot" to retrieve data of all the users of the users collection. Please see an example of same at https://firebase.flutter.dev/docs/firestore/usage/#document--query-snapshots
I expect you are currently using "DocumentSnapshot" to retrieve data of a particular user.
Related
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."
I want to get data from firebase only if the user is not saved in the document. Because I need a or-query, which is not possible in Firebase, I decided to use RxDart's CombinedStreams with two steams:
var streamOne = FirebaseFirestore.instance
.collection('jobs')
.where('jobState', isEqualTo: 1)
.where('userOne', isNotEqualTo: FirebaseAuth.instance.currentUser!.uid)
.snapshots();
var streamTwo = FirebaseFirestore.instance
.collection('jobs')
.where('jobState', isEqualTo: 1)
.where('userTwo', isNotEqualTo: FirebaseAuth.instance.currentUser!.uid)
.snapshots();
But my app shows the data even if the current user is in 'userOne' OR 'userTwo'. Is it possible to avoid this and get the data just if the currentUser is not 'userOne' OR 'userTwo'?
Your logic is flawed: if the UID is in userOne, the second query will still return that document, and vice versa. What you want is actually an AND: the documents where the UID is not in userOne and not in userTwo.
Unfortunately though that query also isn't possible on Firestore, as all not-equal conditions in a query must be on the same field.
There is no way to capture your logic in a single query, and you will have to filter the documents fo userOne and userTwo in your application code instead.
So I want to retrieve name of a user which is inside a field in firestore.
The whole sequence in given in image below.
I want to get the string value 'a' which is inside (chatroom->a_qaz->users->'a').
I am trying to get it with this code but its not working. How to get the field information.
getOtherUserByUsername() async {
return await FirebaseFirestore.instance
.collection("chatroom")
.doc("chatRoomId")
.get();
First of all, let's get the document from your collection.
collection.doc(), as per reference, gets the actual ID as parameter. In your case, you need to specify "a_qaz". After that, you get the document and then you can read the fields. Your code should look like this:
let chatRoom = await FirebaseFirestore.instance
.collection("chatroom")
.doc("a_qaz")
.get();
let users = chatRoom.get("users");
users will store, then, the list of users that's in that field.
In the 1st screen shot there are many documents in collection users. Each documents contains further collection jobPost and that collection contains further documents and its meta data.
What I want here is go to the every document of collection users and further subcollection jobPost and fetch all the documents.
Suppose first it should go to document 1 in collection users, in the document 1 it should fetch all the documnets in subcollection jobPost then it should go to the 2nd document of collection users and then get all the documents in the subcollection jobPost and so on. what will be the query or implementation to this technique
What you're describing is known as a collection group query, which allows you to query all collections with a specific name. Unlike what the name suggests, you can actually read all documents from all subcollections named jobPost that way with:
FirebaseFirestore.instance.collectionGroup('jobPost').get()...
When performing a query, Firestore returns either a QuerySnapshot or a DocumentSnapshot.
A QuerySnapshot is returned from a collection query and allows you to inspect the collection.
To access the documents within a QuerySnapshot, call the docs property, which returns a List containing DocumentSnapshot classes.
But subcollection data are not included in document snapshots because Firestore queries are shallow. You have to make a new query using the subcollection name to get subcollection data.
FirebaseFirestore.instance
.collection('users')
.get()
.then((QuerySnapshot querySnapshot) {
querySnapshot.docs.forEach((doc) {
FirebaseFirestore.instance
.document(doc.id)
.collection("jobPost")
.get()
.then(...);
});
});
**
if you not have field in first collection document then its shows italic thats means its delte by default otherwise if you have field in first collection document then you can access it easily so this is the best way that i share
**
static Future<List<PostSrc>> getAllFeedPosts()async
{
List<PostSrc> allPosts = [];
var query= await FirebaseFirestore.instance.collection("posts").get();
for(var userdoc in query.docs)
{
QuerySnapshot feed = await FirebaseFirestore.instance.collection("posts")
.doc(userdoc.id).collection("userPosts").get();
for (var postDoc in feed.docs ) {
PostSrc post = PostSrc.fromDoc(postDoc);
allPosts.add(post);
}
}
return allPosts;
}
When you go into posts collection there are documents based on userId. And inside a document there is a new collection named userPosts. Inside userposts you can find postId and the details about the post.
I can get specific user post by using this code
postRef = Firestore.instance.collection('posts');
QuerySnapshot snapshot = await postRef
.document(userId)
.collection('userPosts')
.getDocuments();
But I want to get all the user posts without naming a specific user. How could I achieve this?
You can use a collection group query to query documents among all collections with same name.
QuerySnapshot snapshot = await Firestore.instance
.collectionGroup('userPosts')
.getDocuments();