In my application, I have set up a Core Data entity called "Finances". For now it has 2 attributes: money and net-worth.
I wish to write a function that each time it is called, it deletes all results for a specific entity. An example might be:
func resetAttribute(attribute: String) {
}
PS: I have found on the internet a function which was engineered to only delete a specific element of an attribute, which matched to a string. I have modified the code in the following way:
func resetTest() {
if let dataAppDelegatde = UIApplication.shared.delegate as? AppDelegate {
let mngdCntxt = dataAppDelegatde.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "ApplicationFinances")
let predicate = NSPredicate(format: "money != %#", "vdavduabsdpansuryiubj")
fetchRequest.predicate = predicate
do {
let result = try mngdCntxt.fetch(fetchRequest)
print(result.count)
if result.count > 0 {
for object in result {
print(object)
mngdCntxt.delete(object as! NSManagedObject)
}
}
} catch{
}
}
}
Meaning that if money wouldn't have been equals to vdavduabsdpansuryiubj (Meaning never of course) it would have deleted the other values. But this didn't seem to work.
What happens when you run the function? Does it throw an error? Or does it print just fine and runs fine but nothing actually happens when you reload the core data? If this is the case, try adding:
do {
try mngdCntxt.save()
} catch {}
Right after the for loop is over
Related
My first Swift app is a photo library manager, and after rebuilding its Core Data guts half a dozen times, I am throwing up my hands and asking for help. For each photo, there are a few "layers" of work I need to accomplish before I can display it:
Create an Asset (NSManagedObject subclass) in Core Data for each photo in the library.
Do some work on each instance of Asset.
Use that work to create instances of Scan, another NSManagedObject class. These have to-many relationships to Assets.
Look over the Scans and use them to create AssetGroups (another NSManagedObject) in Core Data. Assets and AssetGroups have many-to-many relationships.
For each photo, each layer must complete before the next one starts. I can do multiple photos in parallel, but I also want to chunk up the work so it loads into the UI coherently.
I'm really having trouble making this work gracefully; I've built and rebuilt it a bunch of different ways. My current approach uses singleton subclasses of this Service, but as soon as I call save() on the first one, the work stops.
Service.swift
class Service: NSObject, ObservableObject, NSFetchedResultsControllerDelegate {
var name: String
var predicate: NSPredicate
var minStatus: AssetStatus
var maxStatus: AssetStatus
internal let queue: DispatchQueue
internal let mainMOC = PersistenceController.shared.container.viewContext
internal let privateMOC = PersistenceController.shared.container.newBackgroundContext()
internal lazy var frc: NSFetchedResultsController<Asset> = {
let req = Asset.fetchRequest()
req.predicate = self.predicate
req.sortDescriptors = [NSSortDescriptor(key: #keyPath(Asset.creationDate), ascending: false)]
let frcc = NSFetchedResultsController(fetchRequest: req,
managedObjectContext: self.mainMOC,
sectionNameKeyPath: "creationDateKey",
cacheName: nil)
frcc.delegate = self
return frcc
}()
#Published var isUpdating = false
#Published var frcCount = 0
init(name: String, predicate: NSPredicate? = NSPredicate(value: true), minStatus: AssetStatus, maxStatus: AssetStatus) {
self.name = name
self.predicate = predicate!
self.minStatus = minStatus
self.maxStatus = maxStatus
self.queue = DispatchQueue(label: "com.Ladybird.Photos.\(name)", attributes: .concurrent)
super.init()
self.fetch()
self.checkDays()
}
private func fetch() {
do {
try self.frc.performFetch()
print("\(name): FRC fetch count: \(frc.fetchedObjects!.count)")
} catch {
print("\(name): Unable to perform fetch request")
print("\(error), \(error.localizedDescription)")
}
}
func savePrivate() {
self.privateMOC.perform {
do {
try self.privateMOC.save()
}
catch {
print("\(self.name) could not synchonize data. \(error), \(error.localizedDescription)")
}
}
}
func save() {
do {
try self.privateMOC.save()
self.mainMOC.performAndWait {
do {
try self.mainMOC.save()
} catch {
print("\(self.name) could not synchonize data. \(error), \(error.localizedDescription)")
}
}
}
catch {
print("\(self.name) could not synchonize data. \(error), \(error.localizedDescription)")
}
}
func checkDays() {
// Iterate over days in the photo library
if self.isUpdating { return }
self.isUpdating = true
// self.updateCount = self.frcCount
var daysChecked = 0
var day = Date()
while day >= PhotoKitService.shared.oldestPhAssetDate() {
print("\(name) checkDay \(DateFormatters.shared.key.string(from: day))")
checkDay(day)
var dc = DateComponents()
dc.day = -1
daysChecked += 1
day = Calendar.current.date(byAdding: dc, to: day)!
if daysChecked % 100 == 0 {
DispatchQueue.main.async {
self.save()
}
}
}
self.save()
self.isUpdating = false
}
func checkDay(_ date: Date) {
let dateKey = DateFormatters.shared.key.string(from: date)
let req = Asset.fetchRequest()
req.predicate = NSPredicate(format: "creationDateKey == %#", dateKey)
guard let allAssetsForDateKey = try? self.mainMOC.fetch(req) else { return }
if allAssetsForDateKey.count == PhotoKitService.shared.phAssetsCount(dateKey: dateKey) {
if allAssetsForDateKey.allSatisfy({$0.assetStatusValue >= minStatus.rawValue && $0.assetStatusValue <= maxStatus.rawValue}) {
let frcAssetsForDateKey = self.frc.fetchedObjects!.filter({$0.creationDateKey! == dateKey})
if !frcAssetsForDateKey.isEmpty {
print("\(name): Day \(dateKey) ready for proccessing.")
for a in frcAssetsForDateKey {
self.handleAsset(a)
}
}
}
}
self.save()
}
// implemented by subclasses
func handleAsset(_ asset: Asset) -> Void { }
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
self.frcCount = self.frc.fetchedObjects?.count ?? 0
self.checkDays()
}
}
I have a subclass of this for each of the four steps above. I want the data to flow between them nicely, and in previous implementations it did, but I couldn't chunk it the way I wanted, and it crashed randomly. This feels more controllable, but it doesn't work: calling save() stops the iteration happening in checkDays(). I can solve that by wrapping save() in an async call like DispatchQueue.main.async(), but it has bad side effects — checkDays() getting called while it's already executing. I've also tried calling save() after each Asset is finished, which makes the data move between layers nicely, but is slow as hell.
So rather than stabbing in the dark, I thought I'd ask whether my strategy of "service layers" feels sensible to others who others who have dealt with this kind of problem. It'd also be helpful to hear if my implementation via this Service superclass makes sense.
What would be most helpful is to hear from those with experience how they would approach implementing a solution to this problem: consecutive steps, applied concurrently to multiple Core Data entities, all in the background. There are so many ways to solve pieces of this in Swift — async/await, Tasks & Actors, DispatchQueues, ManagedObjectContext.perform(), container.performBackgroundTask(), Operation… I've tried each of them to mixed success, and what I feel like I need here is a trail map to get out of the forest.
Thanks y'all
I have a simple entity with identifier (constraint) and name fields. In ViewController I try to add data to the database without worrying about duplicates and there really is no duplicate data in the database, but when I try to get records, I get twice as many of them. As I found out, this only happens when I try to write something to the database, and regardless of whether the attempt was successful, the data goes to my NSFetchRequestResult. What is the reason for this behavior?
DB content now:
ViewController:
class ViewController: UIViewController {
let moc = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
override func viewDidLoad() {
super.viewDidLoad()
//if comment this loop I won't get duplicates
for i in 0...5 {
let ent = Entity(context: moc)
ent.identifier = Int16(i)
ent.name = "Username"
try? moc.save() //if the code is not executed for the first time, then the attempt is unsuccessful due to identifier constraint
}
let fetch = NSFetchRequest<NSFetchRequestResult>(entityName: "Entity")
let fetchedEntities = try? moc.fetch(fetch) as? [Entity]
print(fetchedEntities!.count) // Output: 12 (actually only 6 records in the db)
}
}
Change your code where you create the objects to
for i in 0...5 {
let ent = Entity(context: moc)
ent.identifier = Int16(i)
ent.name = "Username"
}
do {
try moc.save()
} catch {
moc.reset()
}
This way you will remove the faulty (duplicate) objects from the context
I am trying to build a to-do list app.
So far I have an entity for storing categories. Within the category entity, it has 3 relationships. One to a task entity, one to an event entity and one to a reminder entity.
In my app, I would like to be able to go into a category and see a tableView filled with tasks, reminders, and events.
So far, my tableView works with just have one child entity. This so done through the following code:
func loadEvents(with request: NSFetchRequest<Event> = Event.fetchRequest()) {
let predicate = NSPredicate(format: "parentCategory.name MATCHES %#", selectedCategory!.name!)
request.predicate = predicate
do {
itemsArray = try context.fetch(request)
} catch {
print(error)
}
print(itemsArray)
tableView.reloadData()
}
The problem happens when I try to add all 3 child types to the same array. Nothing shows up in the table view. (I have support for multiple cell types in my table view too.)
I have tried this code:
func loadItems(with request: NSFetchRequest<Task> = Task.fetchRequest()) {
itemsArray = []
let taskRequest: NSFetchRequest<Task> = Task.fetchRequest()
let predicate = NSPredicate(format: "parentCategory.name MATCHES %#", selectedCategory!.name!)
taskRequest.predicate = predicate
let eventRequest: NSFetchRequest<Event> = Event.fetchRequest()
eventRequest.predicate = predicate
do {
itemsArray.append(try context.fetch(taskRequest))
itemsArray.append(try context.fetch(eventRequest))
} catch {
print(error)
}
print(itemsArray)
tableView.reloadData()
}
But my table view just appears empty. My array is also an array of Any.
Any help on how to add the different child entities to the same array would be greatly appreciated. :)
Answer is below, image is here:
I was searching how to do this for a couple of days and was only able to find people who stored UILocalNotificaations in NSUserDefaults. Saving these in NSUserDefaults seemed wrong to me because it is supposed to be used for small flags. I just now finally figured out how to store notifications in CoreData. This is Using Xcode 7.3.1 and Swift 2.2
First off you need to create a new entity in your CoreDataModel
and then add a single attribute to it. the attribute should be of type Binary Data I named my table/entity "ManagedFiredNotifications" and my attribute "notification". it should look like this:
Image linked in Question above.
Next you need to add an extension to UILocalNotification it should go like this:
extension UILocalNotification {
func save() -> Bool {
let appDelegate = UIApplication.sharedApplication().delegate as? AppDelegate
let firedNotificationEntity = NSEntityDescription.insertNewObjectForEntityForName("ManagedFiredNotifications", inManagedObjectContext: appDelegate!.managedObjectContext)
guard appDelegate != nil else {
return false
}
let data = NSKeyedArchiver.archivedDataWithRootObject(self)
firedNotificationEntity.setValue(data, forKey: "notification")
do {
try appDelegate!.managedObjectContext.save()
return true
} catch {
return false
}
}
}
Now for saving a notification all you need to do is call
UILocalNotification.save()
On the notification you would like to save. my notifications were named 'notification' so I would call notification.save()
To retrieve a notification you need a method like this
func getLocalFiredNotifications() -> [UILocalNotification]? {
let managedObjectContext = (UIApplication.sharedApplication().delegate as? AppDelegate)!.managedObjectContext
let firedNotificationFetchRequest = NSFetchRequest(entityName: "ManagedFiredNotifications")
firedNotificationFetchRequest.includesPendingChanges = false
do {
let fetchedFiredNotifications = try managedObjectContext.executeFetchRequest(firedNotificationFetchRequest)
guard fetchedFiredNotifications.count > 0 else {
return nil
}
var firedNotificationsToReturn = [UILocalNotification]()
for managedFiredNotification in fetchedFiredNotifications {
let notificationData = managedFiredNotification.valueForKey("notification") as! NSData
let notificationToAdd = NSKeyedUnarchiver.unarchiveObjectWithData(notificationData) as! UILocalNotification
firedNotificationsToReturn.append(notificationToAdd)
}
return firedNotificationsToReturn
} catch {
return nil
}
}
Note that this returns an array of UILocalNotifications.
When retrieving these if you plan on removing a few of them and then storing the list again you should remove them when you get them something like this works:
func loadFiredNotifications() {
let notifications = StudyHelper().getLocalFiredNotifications()
if notifications != nil {
firedNotifications = notifications!
} else {
// throw an error or log it
}
classThatRemoveMethodIsIn().removeFiredLocalNotifications()
}
I hope this helps someone who had the same problems that I did trying to implement this.
To my knowledge, the following code (or very close to it) would retrieve one cloudkit instance from the recordtype array...
let pred = NSPredicate(value: true)
let query = CKQuery(recordType: "Stores", predicate: pred)
publicDatabase.performQuery(query, inZoneWithID: nil) { (result, error) in
if error != nil
{
print("Error" + (error?.localizedDescription)!)
}
else
{
if result?.count > 0
{
let record = result![0]
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.txtDesc.text = record.objectForKey("storeDesc") as? String
self.position = record.objectForKey("storeLocation") as! CLLocation
let img = record.objectForKey("storeImage") as! CKAsset
self.storeImage.image = UIImage(contentsOfFile: img.fileURL.path!)
....(& so on)
However, how and when (physical location in code?) would I query so that I could set each cell to the information of each instance in my DiningType record?
for instance, would I query inside the didreceivememory warning function? or in the cellforRowatIndexPath? or other!
If I am misunderstanding in my above code, please jot it down in the notes, all help at this point is valuable and extremely appreciated.
Without a little more information, I will make a few assumptions about the rest of the code not shown. I will assume:
You are using a UITableView to display your data
Your UITableView (tableView) is properly wired to your viewController, including a proper Outlet, and assigning the tableViewDataSource and tableViewDelegate to your view, and implementing the required methods for those protocols.
Your data (for each cell) is stored in some type of collection, like an Array (although there are many options).
When you call the code to retrieve records from the database (in this case CloudKit) the data should eventually be stored in your Array. When your Array changes (new or updated data), you would call tableView.reloadData() to tell the tableView that something has changed and to reload the cells.
The cells are wired up (manually) in tableView(:cellForRowAtIndexPath:). It calls this method for each item (provided you implemented the tableView(:numberOfRowsInSection:) and numberOfSectionsInTableView(_:)
If you are unfamiliar with using UITableView's, they can seem difficult at first. If you'd like to see a simple example of wiring up a UITableView just let me know!
First, I had to take care of the typical cloudkit requirements: setting up the container, publicdatabase, predicate, and query inputs. Then, I had the public database perform the query, in this case, recordtype of "DiningType". Through the first if statement of the program, if an error is discovered, the console will print "Error" and ending further action. However, if no run-time problem is discovered, each result found to be relatable to the query is appended to the categories array created above the viewdidload function.
var categories: Array<CKRecord> = []
override func viewDidLoad() {
super.viewDidLoad()
func fetchdiningtypes()
{
let container = CKContainer.defaultContainer()
let publicDatabase = container.publicCloudDatabase
let predicate = NSPredicate(value: true)
let query = CKQuery(recordType: "DiningType", predicate: predicate)
publicDatabase.performQuery(query, inZoneWithID: nil) { (results, error) -> Void in
if error != nil
{
print("Error")
}
else
{
for result in results!
{
self.categories.append(result)
}
NSOperationQueue.mainQueue().addOperationWithBlock( { () -> Void in
self.tableView.reloadData()
})
}
}
}
fetchdiningtypes()