This is the case - I'm using a simple UITableView that renders records from the CloudKit publicDB. When I run the app, the query operation returns for example returns 2 results (that's all it has currently).
My table view has a refresh control and when I pull to refresh I got zero results, if I continue to do reloads, eventually a result might come out but now always.
The same thing happens with more results as well, I used to have CKLocation type which I queried and the response was always different without any common sense
Some example code (the predicate in this case is TRUEPREDICATE - nothing fancy):
let sort = NSSortDescriptor(key: "creationDate", ascending: false)
let query = CKQuery(recordType: "Tests", predicate: DiscoveryMode.getPredicate())
query.sortDescriptors = [sort]
var operation = CKQueryOperation(query: query)
if lastCursor != nil {
operation = CKQueryOperation(cursor: lastCursor)
}
operation.resultsLimit = 15
operation.recordFetchedBlock = recordFetchBlock
operation.queryCompletionBlock = { [weak self] (cursor:CKQueryCursor!, error:NSError!) in
if cursor != nil {
self!.lastCursor = cursor
}
dispatch_async(dispatch_get_main_queue(), { () -> Void in
Misc.hideLoadingInView(view: self!.view)
self!.tableView.reloadData()
self!.refreshControl.endRefreshing()
if error != nil {
Misc.showErrorInView(view: self!.view, message: error.localizedDescription)
}
})
}
CloudKit.sharedInstance.publicDB.addOperation(operation)
All the recordFetchBlock does is to add objects to a mutable array that the table view uses as dataSource.
I'm new to CloudKit and I'm puzzled is this by design (not returning all the results but some random) or I'm doing something wrong?
I see that you are using a cursor. because of that the 2nd call will start at the point where the first call ended. You have a resultsLimit of 15. When using a cursor, you will only receive records the 2nd time you execute the query if there were more than 15 records. To test if this is the issue just comment out the line where you set the cursor: operation = CKQueryOperation(cursor: lastCursor)
I found the issue, I was trying to do (in the NSPredicate) a radius with a value I read somewhere is in kilometers. Therefore I was trying to query records within 500 meters instead of 500 kilometers and the GPX file I'm using in the simulator has multiple records with a larger distance. Since it simulates movement, that was the reason not to get consistent results.
Now, when I'm using a proper value for the radius all seems to be just fine!
Related
For context, I have a bunch of documents that hold fields similar to a social media post. (photo url link, like count, date uploaded, person who uploaded it, etc.) And I am showing this data in a gallery (lazyvgrid). I do not want to get all of the documents at once so when the user scrolls down the gallery I am getting 20 documents at a time based on how far the user scrolls down the gallery view. I am sorting my get request with:
self.eventsDataCollection.document(currentEventID).collection("eventMedias").order(by: "savesCount", descending: true).limit(to: 20).getDocuments
I have no problem getting the first 20 using this code. How can I get the next 20 and the 20 after that, and so on?
With query cursors in Cloud Firestore, you can split data returned by a query into batches according to the parameters you define in your query.
Query cursors define the start and end points for a query, allowing you to:
Return a subset of the data.
Paginate query results.
Use the startAt() or startAfter() methods to define the start point for a query. Use the endAt() or endBefore() methods to define an endpoint for your query results.
As Dharmaraj mentioned for your case, it will be best if we use Pagination with Firestore.
Paginate queries by combining query cursors with the limit() method to limit the number of documents you would want to show in the gallery. And as you want no definite numbers, but the user should be able to scroll through as long as he wants, and as long as there are documents, I would suggest to put a cursor until the last document, like in the below code sample.
To get the last document,
let first = db.collection("collectionname")
.order(by: "fieldname")
first.addSnapshotListener { (snapshot, error) in
guard let snapshot = snapshot else {
print("Error retrieving cities: \(error.debugDescription)")
return
}
guard let lastSnapshot = snapshot.documents.last else {
// The collection is empty.
return
}
I ended up referencing Dharmaraj's link in his comment.
#Published var isFetchingMoreDocs: Bool = false
private var lastDocQuery: DocumentSnapshot!
public func getUpdatedEventMedias(currentEventID: String, eventMedias: [EventMedia], completion: #escaping (_ eventMedias: [EventMedia]) -> Void) {
self.isFetchingMoreDocs = true
var docQuery: Query!
if eventMedias.isEmpty {
docQuery = self.eventsDataCollection.document(currentEventID).collection("eventMedias").order(by: "savesCount", descending: true).limit(to: 20)
} else if let lastDocQuery = self.lastDocQuery {
docQuery = self.eventsDataCollection.document(currentEventID).collection("eventMedias").order(by: "savesCount", descending: true).limit(to: 20).start(afterDocument: lastDocQuery)
}
if let docQuery = docQuery {
print("GET DOCS")
docQuery.getDocuments { (document, error) in
if let documents = document?.documents {
var newEventMedias: [EventMedia] = []
for doc in documents {
if let media = try? doc.data(as: EventMedia.self) {
newEventMedias.append(media)
}
}
self.lastDocQuery = document?.documents.last
self.isFetchingMoreDocs = false
completion(newEventMedias)
} else if let error = error {
print("Error getting updated event media: \(error)")
self.isFetchingMoreDocs = false
completion([])
}
}
} else {
self.isFetchingMoreDocs = false
completion([])
}
}
As seen in my code, by utilizing:
.order(by: "savesCount", descending: true).limit(to: 20).start(afterDocument: lastDocQuery)
I am able to start exactly where I left off. I should also note that I am only calling this function if !isFetchingMoreDocs - otherwise the func will be called dozens of times in a matter of seconds while scrolling. The most important thing about this code is that I am checking lastDocQuery if it is nil. After the user scrolls all the way to the bottom, the lastDocQuery will no longer be valid and cause a fatal error. Also I am using a custom scroll view that tracks the scroll offset in order to fetch more media and make more calls to firebase.
I am experiencing an inconsistent issue when trying func removeFilterPredicate(_ predicate: MPMediaPredicate) however I never have an issue when trying func addFilterPredicate(_ predicate: MPMediaPredicate)
When I test my app and add the predicate it works every time without fail. When I try to remove the predicate usually it works, but sometimes it does not.
The behavior I expect is to remove the predicate and then a random song that does not match the previous predicate to play
What is actually sometimes happening is after I remove the predicate and skip to next song more songs from the previous predicate still play
I have found if I want to guarantee it to fail I can do so by adding the predicate to only play songs from a specific Artist and then rapidly skip a few songs and then try to remove the predicate.
The way I add the predicate is
func getSongsWithCurrentArtistFor(item: MPMediaItem) -> MPMediaQuery {
let artistPredicate = MPMediaPropertyPredicate(value: item.artist, forProperty: MPMediaItemPropertyArtist, comparisonType: .contains)
let query = MPMediaQuery()
query.addFilterPredicate(artistPredicate)
return query
}
let lockArtist = MediaManager.shared.getSongsWithCurrentArtistFor(item: nowPlaying)
if var items = lockArtist.items {
items.shuffle()
let descriptor = MPMusicPlayerMediaItemQueueDescriptor(itemCollection: MPMediaItemCollection(items: items))
self.mediaPlayer.prepend(descriptor)
}
Which again NEVER fails
To remove the predicate:
func removeArtistLockFor(item: MPMediaItem) -> MPMediaQuery {
let artistPredicate = MPMediaPropertyPredicate(value: item.artist, forProperty: MPMediaItemPropertyArtist)
let query = MPMediaQuery()
query.removeFilterPredicate(artistPredicate)
return query
}
let unlockArtist = MediaManager.shared.removeArtistLockFor(item: nowPlaying)
if var items = unlockArtist.items?.filter({ (item) -> Bool in
return item.mediaType.rawValue <= MPMediaType.anyAudio.rawValue
}) {
items.shuffle()
let descriptor = MPMusicPlayerMediaItemQueueDescriptor(itemCollection: MPMediaItemCollection(items: self.newSongs.shuffled()))
self.mediaPlayer.prepend(descriptor)
}
I am wondering if A) There is an issue with the way I am removing MPMediaPropertyPredicate, B) I need some sort of added method to fix the edge case of rapidly changing song, or C) both.
I know I have previously posted about issues with MPMediaPlayer .. specifically aboutfunc prepend(_ descriptor: MPMusicPlayerQueueDescriptor) but those issues were resolved in ios13. This is a new issue...and the fact that adding the predicate ALWAYS working makes me think this is more of a mistake on my part and not Apple's issue...?
The lines in your removeArtistLockFor function
let query = MPMediaQuery()
query.removeFilterPredicate(artistPredicate)
...appears to be creating a new instance of MPMediaQuery so unless it behaves like a singleton (which from the documentation doesn't appear to be the case), there will be nothing to remove at this point.
Should you be holding on to a reference to the query from when you add the predicate and pass it in to the remove function so you can then do
passedQuery.removeFilterPredicate(artistPredicate)
I have an app that uses CloudKit for sync and I maintain a local cache of records. I have run into a sync scenario that I can't figure out.
I'm using the Public database and when my app is opened, I want to be able to go get all the updated records that my app missed while it was closed, or on a device where the app was just installed.
I can get the updated records by creating a NSPredicate to compare the modificationDate like this:
let predicate = NSPredicate(format: "modificationDate > %#", syncTimestamp as CVarArg)
let query = CKQuery(recordType: recordType, predicate: predicate)
But the part I can't figure out is how to get only the records that have been added to, or removed from, the CloudKit server.
Does anyone know how to do this? I know Apple provides a way for this in the Private database but I'm using the Public one here.
The only thing I can think of so far is to query all the reocrds of a certain recordType, collect all their recordNames and compare to my local cache. But it'd be nice to have smarter way than just pull large amounts of data and comparing huge arrays of recordNames.
CKQuerySubscription(recordType: myRecordType, predicate: predicate, options: [.firesOnRecordCreation, .firesOnRecordDeletion]) works perfectly on public DB.
Here's a code snippet (saving subscription is done with RxCloudKit, but this is beyond the point) -
let predicate = NSPredicate(format: "TRUEPREDICATE")
// the options are different from what you need, just showcasing the possibilities:
let subscription = CKQuerySubscription(recordType: recordTypeTest, predicate: predicate, options: [.firesOnRecordCreation, .firesOnRecordUpdate, .firesOnRecordDeletion, .firesOnce])
let info = CKNotificationInfo()
info.alertLocalizationKey = "NEW_PARTY_ALERT_KEY"
info.soundName = "NewAlert.aiff"
info.shouldBadge = true
subscription.notificationInfo = info
self.publicDB.rx.save(subscription: subscription).subscribe { event in
switch event {
case .success(let subscription):
print("subscription: ", subscription)
case .error(let error):
print("Error: ", error)
default:
break
}
}.disposed(by: self.disposeBag)
I have a view controller that lists data from a firestore database. Inside a firestore collection, I have a bunch of documents with the information shown in the list, and one document called order which contains one field which is an array of strings in the order I want them displayed. My code grabs this:
self.db.collection("officers").document(school).collection(grade).document("order").getDocument {(document, error) in
if let document = document, document.exists {
self.officerNames = (document.data()!["order"] as! Array<String>)
and then is supposed to use the strings in the array order (officerNames) to query the documents in that same collection (all the documents have a different role so it's only getting one document in the snapshot) and display them in the same order as the one set in order (officerNames).
for item in 1...self.officerNames.count {
self.db.collection("officers").document(school).collection(grade).whereField("role", isEqualTo: self.officerNames[item-1]).getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
let officerMessage = document.data()["agenda"] as! String
let officerInfo = document.data()["short"] as! String
(a bunch of code here using that ^ ^ and due to the color I need item to be an integer)
}
}
}
}
I know that if I try printing item before the self.collection("officers")..... the numbers count by one but if I do that in the for document in querySnapshot..... they're all out of order meaning some documents are loaded faster than others. I have read about Async functions in Swift (although I do use those in JavaScript) but am really confused how to use them and hopefully, there is a simpler way to do this. Any way I can wait to make sure the previous document has been loaded and analyzed before iterating through the loop again?
Here's a screenshot of the database:
Honestly, you may want to examine your data structure and see if you can create one that doesn't require multiple queries like this. I can't quite tell what your data structure is, but if you update your question to include it, I can give some suggestions for how to refactor so you don't have to do 2 different get requests.
That being said, since Swift doesn't have promises like JS, it can be tough to keep data in order. For most cases, closures work well, as I wrote about in this blog. But they still won't preserve order in an array of async calls. Assuming you're using some array to store the officer's data, you can declare the size of the array up front by giving each one a default value. This would look something like this:
var officerArray = [Officer](repeating:Officer(), count: self.officerNames.count)
Of course, it'll be different depending on what kind of objects you're populating it with. I'm using some generic Officer object in this case.
Then, rather than appending the newly created Officer object (or whatever you're calling it) to the end of the array, add its value to its particular location in the array.
for item in 1...self.officerNames.count {
self.db.collection("officers").document(school).collection(grade).whereField("role", isEqualTo: self.officerNames[item-1]).getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
let officerMessage = document.data()["agenda"] as! String
let officerInfo = document.data()["short"] as! String
// etc
officerArray[self.officerNames.count-1] = Officer(officerMessage: officerMessage, officerInfo: officerInfo) // or however you're instantiating your objects
}
}
}
}
This preserves the order.
I have some kind of CloudKit indexing issue. When I save records to iCloud using CKModifyRecordsOperation, modifyRecordsCompletionBlock returns no errors. When I query those records using NSPredicate(value: true) or Dashboard, most of the time it misses one or two records.
So say I upload 5 records (no errors), wait some time (~15 secs) to make sure that indexes are updated, and then query them (through dashboard or app's CKQueryOperation). Most of the time it will show 4 records out 5. Again, no errors. Records are in privateDB in customZone.
Here is what's strange: I'm always able to get records that query didn't return by manually typing recordNames in Dashboard (development) under 'Fetch' menu. So it stores them, just doesn't query. When I delete indexes in a dashboard and reassign them, dashboard query will start to return all the results (with previously omitted records too), but after a few more uploads, some will start to be missing from query again.
Here is my CKModifyRecordsOperation:
let operation = CKModifyRecordsOperation(recordsToSave: records, recordIDsToDelete: [])
operation.modifyRecordsCompletionBlock =
{ [weak self] savedRecords, deletedRecordIDs, error in
guard error == nil else { // no errors here ... }
...
//for each item uploaded to iCloud, mark as synced
if let savedRecords = savedRecords{ // all attempted to save records are here
PendingCloudOperations.shared.markAsUploaded(
savedRecords.map{ $0.recordID.recordName })
}
completion(...)
}
operation.savePolicy = .changedKeys // tried .allKeys too
operation.qualityOfService = .userInitiated
self.privateDB.add(operation)
I experimented with record fields (originally date, asset, and reference) trying to see if any of the fields make a problem. But even if I remove all field's (creating a record with no extra fields, just system meta), problem persists. I didn't include CKQueryOperation code, because Dashboard acts same way as the app.
Any ideas?
EDIT:
Here are bare-bones of my fetching function:
var receipts:[FS_Receipt] = []
let query = CKQuery(recordType: myRecordType, predicate: NSPredicate(value: true))
let operation = CKQueryOperation(query: query)
//completion block
operation.queryCompletionBlock = { [weak self] cursor, error in
guard error == nil else {
// doesn't have any errors here
}
completion(...)
}
operation.recordFetchedBlock = { record in
// doesn't return all records here most of the time.
}
operation.qualityOfService = .userInitiated // without this, 'no internet' will NOT return error
operation.resultsLimit = 5000
operation.zoneID = customZoneID
self.privateDB.add(operation)
}