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
Related
I am using Swift 4 to build a single view iOS 11 application that has a UITableViewController that is also defined as a delegate for a NSFetchedResultsController.
class MyTVC: UITableViewController, NSFetchedResultsControllerDeleagate {
var container:NSPersistentContainer? =
(UIApplication.shared.delegate as? AppDelegate)?.persistentContainer
var frc : NSFetchedResultsController<Student>?
override func viewDidLoad() {
container?.performBackgroundTask { context in
// adds 100 dummy records in background
for i in 1...100 {
let student = Student(context: context)
student.name = "student \(i)"
}
try? context.save() // this works because count is printed below
if let count = try? context.count(for: Student.fetchRequest()) {
print("Number of students in core data: \(count)") // prints 100
}
} // end of background inserting.
// now defining frc:
if let context = container?.viewContext {
let request:NSFetchRequest<Student> = Student.fetchRequest()
request.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
frc = NSFetchedResultsController<Student> (
fetchRequest: request,
managedObjectContext: context,
sectionNameKeyPath: nil,
cacheName: nil )
try? frc?.performFetch() // this works and I get no errors
tableView.reloadData()
frc.delegate = self
} // end of frc definition
}
}
If I add one row of Student using the viewContext, the frc will fire the required methods to show it in the tableView. However, the 100 dummy rows are not shown. In fact, If I try to tell the tableview to reload after the insertion is done, my app starts to behave weirdly and becomes buggy, and does not do what it should do (i.e: does not delete rows, does not edit, etc).
But If I restart my app, without calling the dummy insertion, I can see the 100 rows inserted from the previous run.
The only problem is that I can't call tableView.reloadData() from the background thread, so I tried to do this:
// after printing the count, I did this:
DispatchQueue.main.async { [weak self] in
self?.tableView.reloadData() // causes UI to behave weirdly
}
then I tried to call viewContext.perform to reload the table view in the proper thread
func viewDidLoad() {
// code for inserting 100 dummy rows in background thread
// code for defining frc and setting self as delegate
if let context = container?.viewContext {
context.perform { [weak self] in
self?.tableView.reloadData() // that also causes UI to behave weirdly
}
}
}
How can tell my tableview to reload and display the 100 dummy rows in a thread-safe manner?
override func viewDidLoad() {
super.viewDidLoad()
//Always need your delegate for the UI to be set before calling the UI's delegate functions.
frc.delegate = self
//First we can grab any already stored values.
goFetch()
//This chunk just saves. I would consider putting it into a separate function such as "goSave()" and then call that from an event handler.
container?.performBackgroundTask { context in
//We are in a different queue than the main queue, hence "backgroundTask".
for i in 1...100 {
let student = Student(context: context)
student.name = "student \(i)"
}
try? context.save() // this works because count is printed below
if let count = try? context.count(for: Student.fetchRequest()) {
print("Number of students in core data: \(count)") // prints 100
}
//Now that we are done saving its ok to fetch again.
goFetch()
}
//goFetch(); Your other code was running here would start executing before the backgroundTask is done. bad idea.
//The reason it works if you restart the app because that data you didn't let finish saving is persisted
//So the second time Even though its saving another 100 in another queue there were still at least 100 records to fetch at time of fetch.
}
func goFetch() {
if let context = container?.viewContext {
let request:NSFetchRequest<Student> = Student.fetchRequest()
request.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
frc = NSFetchedResultsController<Student> (
fetchRequest: request,
managedObjectContext: context,
sectionNameKeyPath: nil,
cacheName: nil )
try? frc?.performFetch()
//Now that records are both stored and fetched its safe for our delegate to access the data on the main thread.
//To me it would make sense to do a tableView reload everytime data is fetched so I placed this inside o `goFetch()`
DispatchQueue.main.async { [weak self] in
self?.tableView.reloadData()
}
}
}
After a lot of reading about the NSFetchedResultsController and the NSPersistentContainer and finally finding an important piece of information here at SO I think I have a working example.
My code is slightly different since I used a project I had for this. Anyway here is what I did:
In my view controller I had a property for my container
private var persistentContainer = NSPersistentContainer(name: coreDataModelName)
And in viewDidLoad I loaded the persistent store and created my 100 records.
persistentContainer.loadPersistentStores { persistentStoreDescription, error in
if let error = error {
print("Unable to add Persistent Store [\(error)][\(error.localizedDescription)]")
} else {
self.createFakeNotes() // Here 100 elements get created
DispatchQueue.main.async {
self.setupView() // other stuff, not relevant
self.fetchNotes() // fetch using fetch result controller
self.tableView.reloadData()
}
}
}
Below is createFakeNotes() where I use a separate context for inserting the elements in a background thread, this code is pretty much taken from Apple's Core Data programming guide but to make the UI being updated I needed to set automaticallyMergesChangesFromParent to true which I found out in this SO answer
I also delete old notes first to make the testing easier.
private func createFakeNotes() {
let deleteRequest = NSBatchDeleteRequest(fetchRequest: Note.fetchRequest())
do {
try persistentContainer.persistentStoreCoordinator.execute(deleteRequest, with: persistentContainer.viewContext)
} catch {
print("Delete error [\(error)]")
return
}
let privateContext = persistentContainer.newBackgroundContext()
privateContext.automaticallyMergesChangesFromParent = true //Important!!!
privateContext.perform {
let createDate = Date()
for i in 1...100 {
let note = Note(context: privateContext)
note.title = String(format: "Title %2d", i)
note.contents = "Content"
note.createdAt = createDate
note.updatedAt = createDate
}
do {
try privateContext.save()
do {
try self.persistentContainer.viewContext.save()
} catch {
print("Fail saving main context [\(error.localizedDescription)")
}
} catch {
print("Fail saving private context [\(error.localizedDescription)")
}
}
}
You should fetch your data by calling it from viewwillappear and then try to reload your tableview.
override func viewWillAppear(_ animated: Bool) {
getdata()
tableView.reloadData()
}
func getdata() {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
do{
persons = try context.fetch(Person.fetchRequest())
}
catch {
print("fetching failed")
}
}
In my model i've got a function to read in data from firebase.
I call completionHandler(true) when that's done.
This is my viewDidLoad function in my controller that extends UITableViewController.
override func viewDidLoad()
{
super.viewDidLoad()
let activityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.whiteLarge)
tableView.backgroundView = activityIndicatorView
self.activityIndicatorView = activityIndicatorView
activityIndicatorView.startAnimating()
model.readInFirebaseData { (success) in
print("data read in")
activityIndicatorView.stopAnimating()
dataArray = model.firebaseDataArray
self.tableView.reloadData()
}
searchController.searchResultsUpdater = self
searchController.dimsBackgroundDuringPresentation = false
tableView.tableHeaderView = searchController.searchBar
}
But the table remains empty and for whatever reason self.tableView.reloadData() isn't populating the table as i'd like but if I segue from the TableViewController and come back the list is populated.
I can't see exactly where i'm going wrong.
Thanks.
Update:
I still couldn't get it working so instead of a completionHandler i used a delegate. What i did was:
Singleton:
protocol Refresh{
func refreshData()
}
var delegate:Refresh?
func readInFirebaseData()
{
self.ref.child("users").observe(DataEventType.childAdded, with: { (snapshot) in
user.name = value?["name"] as? String ?? ""
self.dict.updateValue(user, forKey: uid)
DispatchQueue.main.async {
self.delegate?.refreshData()
print("main thread dispatch")
}
})
}
The TableViewController:
class ListController: TableViewController, Refresh{
viewDidLoad()
{
model.delegate = self
}
func refreshData() {
print("called")
array = model.array
self.tableView.reloadData()
}
That all works. The only issue really that I don't know the answer to is the DispatchQueue.main.async is getting called everytime firebase reads in a "user". But I put it at the end of the readInFirebase function and nothing was populated on the list. But in any case it works at the moment.
Probably readInFirebaseData method is asynchronous and the callback runs on a thread different from the main one.
Remember that all the UIKit related calls must be run on the main thread.
Try with:
model.readInFirebaseData { (success) in
print("data read in")
dataArray = model.firebaseDataArray
DispatchQueue.main.async {
activityIndicatorView.stopAnimating()
self.tableView.reloadData()
}
}
Be sure to set delegate and dataSource:
tableView.delegate = self
tableView.dataSource = self
And make sure you call reloadData() from Main Thread:
DispatchQueue.main.async {
self.tableView.reloadData()
}
Calling it from background threads would typically not lead to your table reloaded, since this operation is UI-related. Any UI related operations should be performed from main thread.
I am new to swift and I am trying to make this note app. I have split view controller that goes in my first view controller and that view controller connects to a table view controller. Everything works perfectly is just that when I launch the app I have all the notes like I want but when I try to go back to my first view controller and come back to my table view controller, all the notes are duplicated every single time I do it. I tried everything I can try, is there anyone who can help me
my MasterViewController is
import UIKit
class MasterViewController: UITableViewController {
var detailViewController: DetailViewController? = nil
override func viewDidLoad()
{
super.viewDidLoad()
Note.loadNotes() // The problem is here, I think
noteTable = self.tableView
// Do any additional setup after loading the view, typically from a nib.
let addButton = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(insertNewObject(_:)))
navigationItem.rightBarButtonItem = addButton
if let split = splitViewController
{
let controllers = split.viewControllers
detailViewController = (controllers[controllers.count-1] as! UINavigationController).topViewController as? DetailViewController
}
}
My loadNotes function is
class func loadNotes()
{
let defaults:UserDefaults = UserDefaults.standard
let saveData: [NSDictionary]? = defaults.object(forKey: kAllNotes) as? [NSDictionary]
if let data:[NSDictionary] = saveData
{
for i:Int in 0 ..< data.count
{
let n:Note = Note()
n.setValuesForKeys(data[i] as! [String : Any])
allNotes.append(n)
}
}
}
Your loadNotes method keeps appending. The first line of loadNotes should be:
allNotes = [Note]()
Then it starts with an empty array and fills it up.
And why is loadNotes a static method? That's a bad design. Make Notes a normal class and make loadNotes an instance method.
On an unrelated note (no pun intended), do not use UserDefaults to store app data. Only use it to store little bits of information.
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!
I'm trying to insert a default record into my core data entity while the tableview first-time loaded and checked there's no data in the entity.
The data inserted just fine , but the reloadData() didn't work, after navigate to other view and navigate back to the view the data appears. no matter the reloadData() in or out of the .save() method.
override func viewDidLoad() {
let cateContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
let categoryRequest = NSFetchRequest(entityName: "Category")
categoryArray = (try! cateContext.executeFetchRequest(categoryRequest)) as! [Category]
if categoryArray.count == 0 {
let category = NSEntityDescription.insertNewObjectForEntityForName("Category", inManagedObjectContext: cateContext) as! Category
category.sno = "1"
category.category = "General"
category.locate = false
do {
try cateContext.save()
self.categoryTableView.reloadData()
} catch let saveError as NSError {
print("Saving Error : \(saveError.localizedDescription)")
}
}
//self.categoryTableView.reloadData()
}
If your are calling self.categoryTableView.reloadData() in viewDidLoad() method it will not reload your tableView twice. You need to call self.categoryTableView.reloadData() after you have checked if entity existed again.