i have a list of music at my firebase real time database and i am retriving them but i have 1000 musics data and i want to show loader when i reading data and stop loader when if there is a error(internet connection, or something else) or reading completed.
when i turn off the internet i couldn't get the data and can't stop loader to show error alert like there is no internet connection.
please help me how to handle that problem.
here is my code
didload function called from viewdidload()
private var musicArray = [ItemModal]() {
didSet {
view?.updateTableView()
}
}
func didLoad() {
view?.showLoader()
getAllMusics { ItemModal in
self.musicArray = ItemModal
self.view?.hideLoader()
}
}
func getAllMusics(completion: #escaping ([ItemModal]) -> Void) {
var musicArray = [ItemModal]()
ref.child("music").observeSingleEvent(of: .value) { snapshot in
let enumerator = snapshot.children
while let rest = enumerator.nextObject() as? DataSnapshot {
guard let data = try? JSONSerialization.data(withJSONObject: rest.value as Any, options: []) else { return }
if let itemModal = try? JSONDecoder().decode(ItemModal.self, from: data) {
musicArray.append(itemModal)
}
}
completion(musicArray)
}
}
You can use reachability function by using https://github.com/ashleymills/Reachability.swift. To get to notify when the internet is turned off, you can implement reachabilityChanged Notification. In the selector method of reachabilityChanged, you can hide the loader.
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(reachabilityChanged), name: .reachabilityChanged)
}
#objc func changed() {
if reachability?.isReachable {
//Continue success implementation
} else {
view?.hideLoder
//Implement Error handling
}
}
Related
I'm calling a Firestore query that does come back, but I need to ensure completion before moving on with the rest of the code. So I need a completion handler...but for the life of me I can't seem to code it.
// get user info from db
func getUser() async {
self.db.collection("userSetting").getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
let userTrust = document.data()["userTrust"] as! String
let userGrade = document.data()["userGrade"] as! String
let userDisclaimer = document.data()["userDisclaimer"] as! String
var row = [String]()
row.append(userTrust)
row.append(userGrade)
row.append(userDisclaimer)
self.userArray.append(row)
// set google firebase analytics user info
self.userTrustInfo = userTrust
self.userGradeInfo = userGrade
}
}
}
}
Called by:
internal func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
FirebaseApp.configure()
db = Firestore.firestore()
Database.database().isPersistenceEnabled = true
Task {
do {
let userInfo = await getUser()
}
} return true }
I used a Task as didFinishLauncingWithOptions is synchronous and not asynchronous
However, the getUser() still isn't completed before didFinishLauncingWithOptions moves on.
I need the data from getUser as the very next step uses the data in the array, and without it I get an 'out of bounds exception' as the array is still empty.
Also tried using dispatch group within the func getUser(). Again with no joy.
Finally tried a completion handler:
func getUser(completion: #escaping (Bool) -> Void) {
self.db.collection("userSetting").getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
let userTrust = document.data()["userTrust"] as! String
let userGrade = document.data()["userGrade"] as! String
let userDisclaimer = document.data()["userDisclaimer"] as! String
var row = [String]()
row.append(userTrust)
row.append(userGrade)
row.append(userDisclaimer)
self.userArray.append(row)
// set google firebase analytics user info
self.userTrustInfo = userTrust
self.userGradeInfo = userGrade
completion(true)
}
}
}
}
Nothing works. The getUser call isn't completed before the code moves on. Can someone please help. I've searched multiple times, looked at all linked answers but I can not make this work.I'm clearly missing something easy, please help
read this post: Waiting for data to be loaded on app startup.
It explains why you should never wait for data before returning from
function application(_:didFinishLaunchingWithOptions).
To achieve what you need, you could use your first ViewController as a sort of splashscreen (that only shows an image or an activity indicator) and call the function getUser(completion:) in the viewDidLoad() method the ViewController.
Example:
class FirstViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
MyFirestoreDatabaseManager.shared.getUser() { success in
if success {
//TODO: Navigate to another ViewController
} else {
//TODO: Show an error
}
}
}
}
Where obviously MyFirestoreDatabaseManager.shared is the object on which you defined the getUser(completion:) method.
(In your example, I think that you defined that function in the AppDelegate. In that case, you should mark your getUser(completion:) method and all related variables as static. Then replace MyFirestoreDatabaseManager.shared with AppDelegate).
Not 100% sure what you would like to accomplish as I can't see all your code, but try something similar to this, replacing Objects for what you are trying to return from the documents.
You don't want your user's data spread across multiple documents. With Firebase you pay for every document you have to get. Ideally you want all your user's settings within one firebase document. Then create a UserInfo struct that you can decode to using the library CodeableFirebase or the decoder of your choice.
// Create user struct
struct UserInfo: Codable {
var userId: String
var userTrust: String
var userGrade: String
var userDisclaimer: String
}
// get user info from db and decode using CodableFirebase
func getUser() async throws -> UserInfo {
let doc = try await self.db.collection("users").document("userIdHere")
let userInfo = try FirestoreDecoder().decode(UserInfo.self, from: doc.data())
return UserInfo
}
Then you can do this...
Task {
do {
let userInfo = try await getUser()
let userTrust = userInfo.userTrust
let userGrade = userInfo.userGrade
let userDisclaimer = userInfo.userDisclaimer
}
}
I've consulted many variations of background app refresh for Apple Watch so that I can update the complications for my app. However, the process seems very much hit or miss and most of the time it doesn't run at all after some time.
Here is the code I currently have:
BackgroundService.swift
Responsibility: Schedule background refresh and handle download processing and update complications.
import Foundation
import WatchKit
final class BackgroundService: NSObject, URLSessionDownloadDelegate {
var isStarted = false
private let requestFactory: RequestFactory
private let logManager: LogManager
private let complicationService: ComplicationService
private let notificationService: NotificationService
private var pendingBackgroundTask: WKURLSessionRefreshBackgroundTask?
private var backgroundSession: URLSession?
init(requestFactory: RequestFactory,
logManager: LogManager,
complicationService: ComplicationService,
notificationService: NotificationService
) {
self.requestFactory = requestFactory
self.logManager = logManager
self.complicationService = complicationService
self.notificationService = notificationService
super.init()
NotificationCenter.default.addObserver(self,
selector: #selector(handleInitialSchedule(_:)),
name: Notification.Name("ScheduleBackgroundTasks"),
object: nil
)
}
func updateContent() {
self.logManager.debugMessage("In BackgroundService updateContent")
let complicationsUpdateRequest = self.requestFactory.makeComplicationsUpdateRequest()
let config = URLSessionConfiguration.background(withIdentifier: "app.wakawatch.background-refresh")
config.isDiscretionary = false
config.sessionSendsLaunchEvents = true
self.backgroundSession = URLSession(configuration: config,
delegate: self,
delegateQueue: nil)
let backgroundTask = self.backgroundSession?.downloadTask(with: complicationsUpdateRequest)
backgroundTask?.resume()
self.isStarted = true
self.logManager.debugMessage("backgroundTask started")
}
func handleDownload(_ backgroundTask: WKURLSessionRefreshBackgroundTask) {
self.logManager.debugMessage("Handling finished download")
self.pendingBackgroundTask = backgroundTask
}
func urlSession(_ session: URLSession,
downloadTask: URLSessionDownloadTask,
didFinishDownloadingTo location: URL) {
processFile(file: location)
self.logManager.debugMessage("Marking pending background tasks as completed.")
if self.pendingBackgroundTask != nil {
self.pendingBackgroundTask?.setTaskCompletedWithSnapshot(false)
self.backgroundSession?.invalidateAndCancel()
self.pendingBackgroundTask = nil
self.backgroundSession = nil
self.logManager.debugMessage("Pending background task cleared")
}
self.schedule()
}
func processFile(file: URL) {
guard let data = try? Data(contentsOf: file) else {
self.logManager.errorMessage("file could not be read as data")
return
}
guard let backgroundUpdateResponse = try? JSONDecoder().decode(BackgroundUpdateResponse.self, from: data) else {
self.logManager.errorMessage("Unable to decode response to Swift object")
return
}
let defaults = UserDefaults.standard
defaults.set(backgroundUpdateResponse.totalTimeCodedInSeconds,
forKey: DefaultsKeys.complicationCurrentTimeCoded)
self.complicationService.updateTimelines()
self.notificationService.isPermissionGranted(onGrantedHandler: {
self.notificationService.notifyGoalsAchieved(newGoals: backgroundUpdateResponse.goals)
})
self.logManager.debugMessage("Complication updated")
}
func schedule() {
let time = self.isStarted ? 15 * 60 : 60
let nextInterval = TimeInterval(time)
let preferredDate = Date.now.addingTimeInterval(nextInterval)
WKExtension.shared().scheduleBackgroundRefresh(withPreferredDate: preferredDate,
userInfo: nil) { error in
if error != nil {
self.logManager.reportError(error!)
return
}
self.logManager.debugMessage("Scheduled for \(preferredDate)")
}
}
#objc func handleInitialSchedule(_ notification: NSNotification) {
if !self.isStarted {
self.schedule()
}
}
deinit {
NotificationCenter.default.removeObserver(self)
}
}
The flow for the above file's usage is that it will be used by the ExtensionDelegate to schedule background refresh. The first time, it'll schedule a refresh for 1 minute out and then every 15 minutes after that.
Here is the ExtensionDelegate:
import Foundation
import WatchKit
class ExtensionDelegate: NSObject, WKExtensionDelegate {
private var backgroundService: BackgroundService?
private var logManager: LogManager?
override init() {
super.init()
self.backgroundService = DependencyInjection.shared.container.resolve(BackgroundService.self)!
self.logManager = DependencyInjection.shared.container.resolve(LogManager.self)!
}
func isAuthorized() -> Bool {
let defaults = UserDefaults.standard
return defaults.bool(forKey: DefaultsKeys.authorized)
}
func applicationDidFinishLaunching() {
self.logManager?.debugMessage("In applicationDidFinishLaunching")
if isAuthorized() && !(self.backgroundService?.isStarted ?? false) {
self.backgroundService?.schedule()
}
}
func handle(_ backgroundTasks: Set<WKRefreshBackgroundTask>) {
self.logManager?.debugMessage("In handle backgroundTasks")
if !isAuthorized() {
return
}
for task in backgroundTasks {
self.logManager?.debugMessage("Processing task: \(task.debugDescription)")
switch task {
case let backgroundTask as WKApplicationRefreshBackgroundTask:
self.backgroundService?.updateContent()
backgroundTask.setTaskCompletedWithSnapshot(false)
case let urlSessionTask as WKURLSessionRefreshBackgroundTask:
self.backgroundService?.handleDownload(urlSessionTask)
default:
task.setTaskCompletedWithSnapshot(false)
}
}
}
}
When the app is launched from background, it'll try to schedule for the first time in applicationDidFinishLaunching.
From my understanding, WKExtension.shared().scheduleBackgroundRefresh will get called in schedule, then after the preferred time WatchOS will call handle with WKApplicationRefreshBackgroundTask task. Then I will use that to schedule a background URL session task and immediately start it as seen in the updateContent method of BackgroundService. After some time, WatchOS will then call ExtensionDelegate's handle method with WKURLSessionRefreshBackgroundTask and I'll handle that using the handleDownload task. In there, I process the response, update the complications, clear the task, and finally schedule a new background refresh.
I've found it works great if I'm actively working on the app or interacting with it in general. But let's say I go to sleep then the next day the complication will not have updated at all.
Ideally, I'd like for it to function as well as the Weather app complication WatchOS has. I don't interact with the complication, but it reliably updates.
Is the above process correct or are there any samples of correct implementations?
Some of the posts I've consulted:
https://wjwickham.com/posts/refreshing-data-in-the-background-on-watchOS/
https://developer.apple.com/documentation/watchkit/background_execution/using_background_tasks
https://spin.atomicobject.com/2021/01/26/complications-basic-functionality/
Let say I want to add a new item in Playlist entity of CoreData and put it in background thread and push back it to main thread then reflect it on tableView. Well, that code is working fine without background thread implementation.
But when I apply below background kinda code, after createPlaylist is executed, tableView becomes to empty space(without any items showed up), though print(self?.playlists.count) gives the correct rows count.
When dealing with GCD, I put some heavy code in background queue and push back to main queue for UI update in same closure. But it seems not worked here, I google a quit of time but still cannot anchor the issue.
import UIKit
import CoreData
class PlayListViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
var songs = [Song]()
var position = 0
let container = (UIApplication.shared.delegate as! AppDelegate).persistentContainer
private var playlists = [Playlist]()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor(white: 1, alpha: 1)
tableView.register(UITableViewCell.self, forCellReuseIdentifier: "playlistCell")
configureLayout()
getAllPlaylists()
}
// MARK: Core data functions
func getAllPlaylists() {
do {
let context = self.container.viewContext
playlists = try context.fetch(Playlist.fetchRequest())
DispatchQueue.main.async { [weak self] in
self?.tableView.reloadData()
}
print("count: \(playlists.count)")
// printThreadStats()
} catch {
print("getAllPlaylists failed, \(error)")
}
}
func createPlaylist(name: String) {
container.performBackgroundTask { context in
let newPlaylist = Playlist(context: context)
newPlaylist.name = name
do {
try context.save()
self.playlists = try context.fetch(Playlist.fetchRequest())
DispatchQueue.main.async { [weak self] in
self?.tableView.reloadData()
print(self?.playlists.count)
}
} catch {
print("Create playlist failed, \(error)")
}
}
}
// MARK: tableView data source implementation
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return playlists.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let playlist = playlists[indexPath.row]
let cell = tableView.dequeueReusableCell(withIdentifier: "playlistCell", for: indexPath)
cell.textLabel?.text = playlist.name
// cell.detailTextLabel?.text = "2 songs"
return cell
}
auto generated fetchRequest and Property defining
import Foundation
import CoreData
extension Playlist {
#nonobjc public class func fetchRequest() -> NSFetchRequest<Playlist> {
return NSFetchRequest<Playlist>(entityName: "Playlist")
}
#NSManaged public var name: String?
}
For the first call of func getAllPlaylists(), you are calling this on main thread from viewDidLoad(). So following lines are executed on main thread.
let context = self.container.viewContext
playlists = try context.fetch(Playlist.fetchRequest())
Next time inside the createPlaylist method, you are performing add playlist task in background context (not on main thread). So following lines are executed on background thread.
self.playlists = try context.fetch(Playlist.fetchRequest())
Also note that, first time we are using viewContext to fetch playlists and second time a backgroundContext. This mix up causes the UI to not show expected result.
I think these two methods could be simplified to -
func getAllPlaylists() {
do {
let context = self.container.viewContext
playlists = try context.fetch(Playlist.fetchRequest())
// DispatchQueue.main.async not necessary, we are already on main thread
self.tableView.reloadData()
print("count: \(playlists.count)")
} catch {
print("getAllPlaylists failed, \(error)")
}
}
func createPlaylist(name: String) {
container.performBackgroundTask { context in
let newPlaylist = Playlist(context: context)
newPlaylist.name = name
do {
try context.save()
DispatchQueue.main.async { [weak self] in
self?.getAllPlaylists()
}
} catch {
print("Create playlist failed, \(error)")
}
}
}
After 5 hours' digging today, I found the solution. I'd like put my solution and code below, because the stuff about "How to pass NSManagedObject instances between queues in CoreData" is quite rare && fragmentation, not friendly to newbies of SWIFT.
The thing is we want to do heavy CoreData task on background thread and reflect the changes in UI on foreground(main thread). Generally, we need to create a private queue context(privateMOC) and perform the heavy CoreData task on this private context, see below code.
For reuse purpose, I put CoreData functions separately.
import UIKit
import CoreData
struct CoreDataManager {
let managedObjectContext: NSManagedObjectContext
private let privateMOC = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
let coreDataStack = CoreDataStack()
static let shared = CoreDataManager()
private init() {
self.managedObjectContext = coreDataStack.persistentContainer.viewContext
privateMOC.parent = self.managedObjectContext
}
func fetchAllPlaylists(completion: #escaping ([Playlist]?) -> Void) {
privateMOC.performAndWait {
do {
let playlists: [Playlist] = try privateMOC.fetch(Playlist.fetchRequest())
print("getAllPlaylists")
printThreadStats()
print("count: \(playlists.count)")
completion(playlists)
} catch {
print("fetchAllPlaylists failed, \(error), \(error.localizedDescription)")
completion(nil)
}
}
}
func createPlaylist(name: String) {
privateMOC.performAndWait {
let newPlaylist = Playlist(context: privateMOC)
newPlaylist.name = name
synchronize()
}
}
func deletePlaylist(playlist: Playlist) {
privateMOC.performAndWait {
privateMOC.delete(playlist)
synchronize()
}
}
func updatePlaylist(playlist: Playlist, newName: String) {
...
}
func removeAllFromEntity(entityName: String) {
...
}
func synchronize() {
do {
// We call save on the private context, which moves all of the changes into the main queue context without blocking the main queue.
try privateMOC.save()
managedObjectContext.performAndWait {
do {
try managedObjectContext.save()
} catch {
print("Could not synchonize data. \(error), \(error.localizedDescription)")
}
}
} catch {
print("Could not synchonize data. \(error), \(error.localizedDescription)")
}
}
func printThreadStats() {
if Thread.isMainThread {
print("on the main thread")
} else {
print("off the main thread")
}
}
}
And Apple has a nice template for it Using a Private Queue to Support Concurrency
Another helpful link: Best practice: Core Data Concurrency
The real tricky thing is how to connect it with your view or viewController, the really implementation. See below ViewController code.
// 1
override func viewDidLoad() {
super.viewDidLoad()
// some layout code
// execute on background thread
DispatchQueue.global().async { [weak self] in
self?.fetchAndReload()
}
}
// 2
private func fetchAndReload() {
CoreDataManager.shared.fetchAllPlaylists(completion: { playlists in
guard let playlists = playlists else { return }
self.playlists = playlists
})
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
// 3
#objc func createNewPlaylist(_ sender: Any?) {
let ac = UIAlertController(title: "Create New Playlist", message: "", preferredStyle: .alert)
ac.addTextField { textField in
textField.placeholder = "input your desired name"
}
ac.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
ac.addAction(UIAlertAction(title: "Done", style: .default, handler: { [weak self] _ in
guard let textField = ac.textFields?.first, let newName = textField.text, !newName.isEmpty else { return }
// check duplicate
if let playlists = self?.playlists {
if playlists.contains(where: { playlist in
playlist.name == newName
}) {
self?.duplicateNameAlert()
return
}
}
DispatchQueue.global().async { [weak self] in
CoreDataManager.shared.createPlaylist(name: newName)
self?.fetchAndReload()
}
}))
present(ac, animated: true)
}
Let me break down it:
First in viewDidload, we call fetchAndReload on background thread.
In fetchAndReload function, it brings out all the playlist(returns data with completion handler) and refresh the table on main thread.
We call createPlaylist(name: newName) in background thread and reload the table on main thread again.
Well, this is the 1st time I deal with Multi-threading in CoreData, if there is any mistake, please indicate it. Allright, that's it! Hope it could help someone.
I am coding since January 2019 and this is my first post here.
I am using Swift and Firestore. In my App is a tableView where I display events loaded out of a single Document with an array of events inside as [String: [String:Any]]. If the user wants to get more infos about an event he taps on it. In the background the TableViewController will open a new "DetailEventViewController" with a segue and give it the value of the eventID in the tapped cell.
When the user is on the DetailViewController Screen the app will download a new Document with the EventID as key for the document.
I wanna save this Data out of Firestore in a Struct called Event. For this example just with Event(eventName: String).
When I get all the data I can print it directly out but I can't save it in a variable and print it out later. I really don't know why. If I print the struct INSIDE the brackets where I get the data its working but if I save it into a variable and try to use this variable it says its nil.
So how can I fetch data out of Firestore and save in just a Single ValueObject (var currentEvent = Event? -> currentEvent = Event.event(for: data as [String:Any]) )
I search in google, firebaseDoc and stackoverflow but didn't find anything about it so I tried to save all the singe infos of the data inside a singe value.
// Struct
struct Event {
var eventName: String!
static func event(for eventData: [String:Any]) -> Event? {
guard let _eventName = eventData["eventName"] as? String
else {
print("error")
return nil
}
return Event(eventName: _eventName)
}
// TableView VC this should work
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "ShowEventDetailSegue" {
if let ShowEvent = segue.destination as? DetailEventViewController, let event = eventForSegue{
ShowEvent.currentEventId = event.eventID
}
}
}
// DetailViewController
var currentEvent = Event()
var currentEventId: String?
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
guard let _eventID = currentEventId else {
print("error in EventID")
return}
setupEvent(eventID: _eventID) /* currentEvent should be set here */
setupView(event: currentEvent) /* currentEvent has after "setupEvent" the value of nil */
}
func setupEvent(eventID: String) {
let FirestoreRef = Firestore.firestore().collection("events").document(eventID)
FirestoreRef.getDocument { (document, error) in
if let err = error {
debugPrint("Error fetching docs: \(err)")
SVProgressHUD.showError(withStatus: "Error in Download")
}else {
if let document = document, document.exists {
guard let data = document.data() else {return}
let eventData = Event.event(for: data as [String:Any])
print(eventData)
//here all infos are printed out - so I get them
self.currentEvent = eventData!
//Here is the error.. I can't save the fetched Data in my single current Event
} else {
SVProgressHUD.showError(withStatus: "Error")
}
}
}
}
func setupView(event: Event) {
self.titleLabel.text = event.eventName
}
I expect that the function setupEvents will give the currentEvent in the DetailViewController a SINGLEvalue cause its a SINGLE document not an array. So I can use this single Eventvalue for further actions. Like starting a new segue for a new ViewController and just push the Event there not
I am trying to do dynamic picker view which shows extra data whenever I will get new input in data base.
At this moment I am using notification and observer to take care of real time updates. Also I am removing all items from string array to get just one newest record - it is not what i want.
override func viewDidLoad() {
super.viewDidLoad()
pickerView.delegate = self
pickerView.dataSource = self
pickerView.sizeToFit()
NotificationCenter.default.addObserver(forName: SEARCH_RESULT, object: nil, queue: nil, using: catchNotificationForSearchResult)
}
func catchNotificationForSearchResult(_notification: Notification) {
let _resultSearch = _notification.object as! [Class]
for _result in _resultSearch {
_stringArray.removeAll()
_stringArray.append("AAA : \(_result.aaa), BBB \(_result.bbb), CCC : \(_result.ccc)")
pickerView.reloadAllComponents()
}
}
AppDelegate:
fun test() {
let _fetchRequest:NSFetchRequest<Class> = Class.fetchRequest()
do {
let _searchResults = try DataBaseController.getContext().fetch(_fetchRequest)
NotificationCenter.default.post(name: SEARCH_RESULT, object: _searchResults)
} catch {
print("Error \(error)")
}
}
Thanks in advance!