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!
Related
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
}
}
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.
With removeObserver(withHandle in Swift 3, the Observer is not removed on viewDidDisappear
var query = FIRDatabaseQuery()
var postRef: FIRDatabaseReference!
var postRefHandle: FIRDatabaseHandle?
override func viewDidLoad() {
super.viewDidLoad()
postRef = baseRef.child("Posts")
}
override func viewDidDisappear(_ animated: Bool) {
super.viewDidDisappear(animated)
if postRefHandle != nil {
//try 1:
//postRef.removeObserver(withHandle: postRefHandle!)
//try 2:
//postRef.queryOrdered(byChild: "sortTimestamp").removeObserver(withHandle: postRefHandle!)
//try 3:
//query.removeObserver(withHandle: postRefHandle!)
}
//try 4:
//postRef.removeAllObservers() //works
}
func getPosts()
{
var count = 20
query = postRef.queryOrdered(byChild: "sortTimestamp")
postRefHandle = query.queryLimited(toFirst: UInt(count)).observe(.childAdded //etc.
}
So I tried the three methods in viewDidDisappear, but the observer is not removed.
try 3 query.removeObserver(withHandle: postRefHandle!) as by answer from Firebase, how do I return a handle so that I can call removeObserver? by frank-van-puffelen
The only one that does work is the one outlined in try 4.
Any reason why I cannot remove the Observer with removeObserver(withHandle? (try 1 - 3)
Also "query.queryLimited(toFirst: UInt(count)).observe(.childAdded" does not get the latest data from Firebase. I was under the impression the observe always gets the updated data, as opposed to observeSingleEvent. Why does it not do that?
Any suggestions are much appreciated.
If you have the following code:
var postsRef: FIRDatabaseReference!
var postRefHandle: FIRDatabaseHandle!
var query = FIRDatabaseQuery()
func addHandler() {
self.postsRef = self.ref.child("posts")
var count = 20
self.query = self.postsRef.queryOrdered(byChild: "sortTimestamp")
self.postRefHandle = self.query.queryLimited(toFirst: UInt(count)).observe(.childAdded, with: { snapshot in
print(snapshot)
})
}
and at a later time you do this function
self.postsRef.removeObserver(withHandle: self.postRefHandle!)
It removes the observer. This is tested code.
To the second part of your question: querySingleEvent and observe do the same thing data wise but have different behaviors. They will both always get current data - modified by startAt, endAt, equalTo etc.
observeSingleEvent returns the data, does NOT leave an observer so you
will not be notified if that data changes
observe returns the data and leaves an observer attached to the node
and will notify you of future changes.
.childAdded: when any children are added to the node
.childChanges: when any children change in the node
.childRemoved: when a child is removed.
How I'm Able to Achieve this is by removing child reference.
var recentRef: FIRDatabaseReference!
recentRef.child("\(groupId)").observe(.value, with: { (snapshot) in
recentRef.removeAllObservers() // not_working
recentRef.child("\(groupId)").removeAllObservers() //working
if let obj = snapshot.value as? [String: AnyObject] {
//... code here
}
})
You can achieve this without making a query also(Swift 4) -
This removes the reference of the observer properly and works for me.
private let ref = Database.database().reference().child("classTalks")
private var refHandle: DatabaseHandle!
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear()
refHandle = ref.observe(.value, with: { (snapshot) in
...
})
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear()
ref.removeObserver(withHandle: refHandle)
}
I have some CoreData base wich I'm used in my TableView.
When I'm tried to clear those base in other View I have a message in my console log.
CoreData: error: Serious application error. An exception was caught from the delegate of NSFetchedResultsController during a call to -controllerDidChangeContent:.
Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (0) must be equal to the number of rows contained in that section before the update (3), plus or minus the number of rows inserted or deleted from that section (0 inserted, 0 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out). with userInfo (null)
for deleting CoreData Array I'm used this code
self.historyArray.removeAll()
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "History")
fetchRequest.returnsObjectsAsFaults = false
do {
let results = try managedContext.executeFetchRequest(fetchRequest)
for managedObject in results
{
let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
managedContext.deleteObject(managedObjectData)
}
} catch {
print("Detele all data")
}
I know I need to reload TableView, but how can I do this in other View?
ill tried this, but this code don't work.
var tableViewHistoryClass = HistoryView()
self.tableViewHistoryClass.tableView.reloadData()
Please help me to fix this message.
You can achieve this by using notification.
create observer in viewDidLoad method where you can display your table view data.
override func viewDidLoad() {
super.viewDidLoad()
NSNotificationCenter.defaultCenter().addObserver(self, selector:"refreshTableView", name: "reloadTable", object: nil)
}
func refreshTableView () {
self.tableView.reloadData()
}
Second view controller
-> In this view controller you can change your data( if you want to do) or send data object
NSNotificationCenter.defaultCenter().postNotificationName("reloadTable", object: nil)
so like this it will reload your table view.
One solution is to notify your tableview when data is removed.
When data is removed your code post notifications :
do {
let results = try managedContext.executeFetchRequest(fetchRequest)
for managedObject in results
{
let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
managedContext.deleteObject(managedObjectData)
NSNotificationCenter
.defaultCenter()
.postNotificationName("dataDeleted", object: self)
}
}
And in controller where is your tableview add an observer for this notification:
override func viewDidLoad() {
NSNotificationCenter
.defaultCenter()
.addObserver(
self,
selector: #selector(viewController.reloadTableView),
name: "dataDeleted",
object: nil)
}
func reloadTableView() {
self.tableview.reloadData
}
Thanks all for answers!
I'm created new method, all my Clear CoreData function i added to my View in which i have TableView for showing all data from CoreData :P
override func viewDidLoad() {
super.viewDidLoad()
NSNotificationCenter.defaultCenter().addObserver(self, selector:"clearCoreDataArray", name: "clearAllData", object: nil)
}
func clearCoreDataArray() {
historyArray.removeAll()
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "History")
fetchRequest.returnsObjectsAsFaults = false
do
{
let results = try managedContext.executeFetchRequest(fetchRequest)
for managedObject in results
{
let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
managedContext.deleteObject(managedObjectData)
}
} catch {
print("Detele all data")
}
self.tableView.reloadData()
}
and in View when I'm need to use this method i use this code
NSNotificationCenter.defaultCenter().postNotificationName("clearAllData", object: self)
now i don't have any CoreData warnings
My Game Center Authentication is not working. When I build and run, it won't show my username.. has signed in. Also, when I try to add my score I get a screen that says "no data availible". Heres my code.
override func viewDidLoad() {
super.viewDidLoad()
gcAuthPlayer()
}
#IBAction func GCButton(sender: AnyObject) {
saveHighScore(GameScene().highScoreNumer)
showLeaderBoard()
if GameScene().currentScore > GameScene().highScoreNumer{
saveHighScore(GameScene().currentScore)
}
}
func showLeaderBoard(){
let viewController = self.view.window?.rootViewController
let gcvc = GKGameCenterViewController()
gcvc.gameCenterDelegate = self
viewController?.presentViewController(gcvc, animated: true, completion: nil)
}
func saveHighScore(number: Int){
if GKLocalPlayer.localPlayer().authenticated{
let scoreReporter = GKScore(leaderboardIdentifier: "myleaderboard")
scoreReporter.value = Int64(number)
let scoreArray : [GKScore] = [scoreReporter]
GKScore.reportScores(scoreArray, withCompletionHandler: nil)
}
}
func gcAuthPlayer(){
let localPlayer = GKLocalPlayer.localPlayer()
localPlayer.authenticateHandler = {
(view, error) in
if view != nil{
self.presentViewController(view!, animated: true, completion: nil)
}else{
print(GKLocalPlayer.localPlayer().authenticated)
}
}
}
func gameCenterViewControllerDidFinish(gameCenterViewController: GKGameCenterViewController) {
gameCenterViewController.dismissViewControllerAnimated(true, completion: nil)
}
This code makes no sense
saveHighScore(GameScene().highScoreNumer)
showLeaderBoard()
if GameScene().currentScore > GameScene().highScoreNumer{
saveHighScor
You are creating a new instance of GameScene everytime you try to update the score and therefore your score is nil
I would need to see some more code but for now you need to change the score property in your game scene. For example make it a static property so you can get it in other classes.
class GameScene: SKScene {
static var currentScore = 0
static var highscoreNumber = 0
}
Than in your Scenes or ViewController you can get it like so
GameScene.currentScore = 5
GameScene.highscoreNumber = 5
Just remember that you have to reset the score to 0 everytime you restart your gameScene because it a static property.
GameScene.currentScore = 0
GameScene.highscoreNumber = 0
Than your code to post the score should look like this
saveHighScore(GameScene.highScoreNumer)
showLeaderBoard()
if GameScene.currentScore > GameScene.highScoreNumer{
saveHighScor
Your score reporting code should also handle the error and actually do the completion handler. So change it to something like this.
/// Save leaderboard progress
func reportLeaderboardProgress(value: Int, leaderboardID: String) {
let scoreReporter = GKScore(leaderboardIdentifier: leaderboardID)
scoreReporter.value = Int64(value)
GKScore.reportScores([scoreReporter]) { error in // Trailing Closure syntax
if let error = error {
print(error.localizedDescription)
return
}
print("Reported leaderboard progress \(value) to leaderboardID \(leaderboardID)")
}
}
It is also a good idea to move that code into another class to keep your overall code cleaner and more reusable.
For a nice and simple example check this helper on gitHub.
https://github.com/jackcook/GCHelper
Let me know how it goes.