I am describing some color information in a Core Data diagram. The entity is a color, and the attributes are color components.
I am struggling with two aspects: how to delete an color object from the graph, and secondly, (bonus question?), how could I identify duplicate colors?
In my AppDelegate, I have a core data stack like this:
lazy var persistentContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: "DD")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
// Replacing this implementation with code to handle the error appropriately.
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
// MARK: - Core Data Saving support
func saveContext () {
print(#function)
let context = persistentContainer.viewContext
if context.hasChanges {
do {
try context.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
and where I'm trying to delete the color, I have this:
func deleteColor(_ sender:UIButton) {
let i : Int = (sender.layer.value(forKey: "index")) as! Int
print(#function, "object to delete: ", i)
let managedContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
colors.remove(at: i)
do {
try managedContext.save()
} catch let error as NSError {
print("Error While Saving Data: \(error.userInfo)")
}
recentColorCollection!.reloadData()
}
Variables are:
var colors = [RecentColorEntity]()
var colorEntity = "RecentColorEntity"
I'm not getting any errors, but the objects are not being deleted.. Can someone help me figure out what I'm doing wrong
colors.remove(at: i)
just removes the color from your colors array in memory. You need to delete the actual object, like this
context.delete(colorObject)
and save.
Related
**this is to how to create a login validation form to move from login to next view controller **
**fetching the data from database**
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
return
}
**it stores the data**
let managedContext = appDelegate.persistentContainer.viewContext
//it fetches the data
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Details")
**validation code to check it but the condition fails**
do {
let result = try managedContext.fetch(fetchRequest)
for data in result as! [NSManagedObject] {
if ([emailid.text].count != 0 && [password.text].count != 0){
if (emailid.text == data.value(forKey: "emailId") as? String) && (password.text == data.value(forKey: "passWord") as? String){
let secondvc = storyboard?.instantiateViewController(withIdentifier: "loginVcID") as! loginVc
self.navigationController?.pushViewController(secondvc, animated: true)
}
in this condition it is not moving to next view controller
to check another condition
}
else {
self.label.text = "enter a valid data"
}
}
}
**when it fails it goes to catch to show that**
catch
{
print("Failed")
}
}
}
**this code is for registration to save into database**
**to create a database and store the value**
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
let managedContext = appDelegate.persistentContainer.viewContext
let detailEntity = NSEntityDescription.entity(forEntityName: "Details", in: managedContext)!
** creation of database**
let detail = NSManagedObject(entity: detailEntity, insertInto: managedContext)
detail.setValue(username.text, forKeyPath: "userName")
detail.setValue(emailid.text, forKey: "emailId")
detail.setValue(password.text, forKey: "passWord")
detail.setValue(city.text, forKey: "city")
**saving the data**
do {
try managedContext.save()
}
** it display whatever in that method**
catch let error as NSError
{
its shows error when it fails
print("Could not save. (error), (error.userInfo)")
}
Go to you appDelegate, you will find a line // MARK: - Core Data stack & // MARK: - Core Data Saving support, remove the saveContext() function & also remove persistentContainer.. Then
Add this class to your project
final class PersistenceManager {
private init() {}
static let shared = PersistenceManager()
// MARK: - Core Data stack
lazy var persistentContainer: NSPersistentContainer = {
/*
The persistent container for the application. This implementation
creates and returns a container, having loaded the store for the
application to it. This property is optional since there are legitimate
error conditions that could cause the creation of the store to fail.
*/
let container = NSPersistentContainer(name: "ProjectNAME")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
/*
Typical reasons for an error here include:
* The parent directory does not exist, cannot be created, or disallows writing.
* The persistent store is not accessible, due to permissions or data protection when the device is locked.
* The device is out of space.
* The store could not be migrated to the current model version.
Check the error message to determine what the actual problem was.
*/
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
lazy var context = persistentContainer.viewContext
// MARK: - Core Data Saving support
func save() {
if context.hasChanges {
do {
try context.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
func fetch<T: NSManagedObject>(_ objectType: T.Type) -> [T] {
let entityName = String(describing: objectType)
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
do {
let fetchedObjects = try context.fetch(fetchRequest) as? [T]
return fetchedObjects ?? [T]()
} catch {
return [T]()
}
}
func deleteAll<T: NSManagedObject>(_ objectType: T.Type) {
let entityName = String(describing: objectType)
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
do {
try persistentContainer.persistentStoreCoordinator.execute(deleteRequest, with: context)
} catch {
print(error.localizedDescription)
}
}
func delete(_ object: NSManagedObject) {
context.delete(object)
save()
}
}
To fetch data
PersistenceManager.shared.fetch(User.self)
To delete data
PersistenceManager.shared.delete(user)
To create user
let newUser = Users(context: PersistenceManager.shared.context)
newUser.name = "Zero Cool"
newUser.password = "qwerty"
PersistenceManager.shared.save()
for the life of me I cannot figure out why I'm not getting anything saved to CoreData. I added CoreData.framework in the build phases but still nothing when I look at the Model.sqlite.
AppDelegate
lazy var persistentContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: "Model")
container.loadPersistentStores(completionHandler: {
(storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
func saveContext () {
let context = persistentContainer.viewContext
if context.hasChanges {
do {
try context.save()
} catch {
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
then in my MainViewController
var timer : Timer?
var distance = Measurement(value: 0, unit: UnitLength.meters)
var run: Run! //name of the entity
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
//...
private func saveRun() {
print("saveRun")
let newRun = Run(context: context)
print("got past core data")
newRun.distance = distance.value
newRun.duration = Int16(seconds)
newRun.timestamp = Date()
for locations in locationList {
let locationObject = Location(context: context)
locationObject.timestamp = locations.timestamp
locationObject.latitude = locations.coordinate.latitude
locationObject.longitude = locations.coordinate.longitude
newRun.addToLocations(locationObject)
(UIApplication.shared.delegate as! AppDelegate).saveContext()
run = newRun
}
}
So... I'm a complete idiot. Its working with the code I posted. The screwup was with an error in my making code and not knowing how to use Liya properly. Thanks for everyones help
#Francesco Deliro
Good to know. I'll keep that in mind
Thanks for everyones help
Core Data expects to be run on a single thread. Even though that thread doesn’t have to be the main thread, Core Data was not designed to be accessed from different threads.
I am having issue while using private managedObjectContextfor saving data in background. I am new to CoreData. I am using Parent-Child approach for NSManagedObjectContext but facing several issues.
Errors arise when I tap reload button multiple times
Errors:
'NSGenericException', reason: Collection <__NSCFSet: 0x16e47100> was mutated while being enumerated
Some times : crash here try managedObjectContext.save()
Sometimes Key value coding Compliant error
My ViewController class
class ViewController: UIViewController {
var jsonObj:NSDictionary?
var values = [AnyObject]()
#IBOutlet weak var tableView:UITableView!
override func viewDidLoad() {
super.viewDidLoad()
getData()
saveInBD()
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.saved(_:)), name: "kContextSavedNotification", object: nil)
}
//Loding json data from a json file
func getData(){
if let path = NSBundle.mainBundle().pathForResource("countries", ofType: "json") {
do {
let data = try NSData(contentsOfURL: NSURL(fileURLWithPath: path), options: NSDataReadingOptions.DataReadingMappedIfSafe)
do {
jsonObj = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers) as? NSDictionary
} catch {
jsonObj = nil;
}
} catch let error as NSError {
print(error.localizedDescription)
}
} else {
print("Invalid filename/path.")
}
}
**Notification reciever**
func saved(not:NSNotification){
dispatch_async(dispatch_get_main_queue()) {
if let data = DatabaseManager.sharedInstance.getAllNews(){
self.values = data
print(data.count)
self.tableView.reloadData()
}
}
}
func saveInBD(){
if jsonObj != nil {
guard let nameArray = jsonObj?["data#"] as? NSArray else{return}
DatabaseManager.sharedInstance.addNewsInBackGround(nameArray)
}
}
//UIButton for re-saving data again
#IBAction func reloadAxn(sender: UIButton) {
saveInBD()
}
}
**Database Manager Class**
public class DatabaseManager{
static let sharedInstance = DatabaseManager()
let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
private init() {
}
func addNewsInBackGround(arr:NSArray) {
let jsonArray = arr
let moc = managedObjectContext
let privateMOC = NSManagedObjectContext(concurrencyType: .PrivateQueueConcurrencyType)
privateMOC.parentContext = moc
privateMOC.performBlock {
for jsonObject in jsonArray {
let entity = NSEntityDescription.entityForName("Country",
inManagedObjectContext:privateMOC)
let managedObject = NSManagedObject(entity: entity!,
insertIntoManagedObjectContext: privateMOC) as! Country
managedObject.name = jsonObject.objectForKey("name")as? String
}
do {
try privateMOC.save()
self.saveMainContext()
NSNotificationCenter.defaultCenter().postNotificationName("kContextSavedNotification", object: nil)
} catch {
fatalError("Failure to save context: \(error)")
}
}
}
func getAllNews()->([AnyObject]?){
let fetchRequest = NSFetchRequest(entityName: "Country")
fetchRequest.resultType = NSFetchRequestResultType.DictionaryResultType
do {
let results =
try managedObjectContext.executeFetchRequest(fetchRequest)
results as? [NSDictionary]
if results.count > 0
{
return results
}else
{
return nil
}
} catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
return nil
}
}
func saveMainContext () {
if managedObjectContext.hasChanges {
do {
try managedObjectContext.save()
} catch {
let nserror = error as NSError
print("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
}
You can write in background and read in the main thread (using different MOCs like you do). And actually you're almost doing it right.
The app crashes on the try managedObjectContext.save() line, because saveMainContext is called from within the private MOC's performBlock. The easiest way to fix it is to wrap the save operation into another performBlock:
func saveMainContext () {
managedObjectContext.performBlock {
if managedObjectContext.hasChanges {
do {
try managedObjectContext.save()
} catch {
let nserror = error as NSError
print("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
}
Other two errors are a little more tricky. Please, provide more info. What object is not key-value compliant for what key? It's most likely a JSON parsing issue.
The first error ("mutated while being enumerated") is actually a nasty one. The description is pretty straight forward: a collection was mutated by one thread while it was enumerated on the other. Where does it occur?
One possible reason (most likely one, I would say) is that it is indeed a Core Data multithreading issue. Despite the fact that you can use several threads, you can only use core data objects within the thread they were obtained on. If you pass them to another thread, you'll likely run into an error like this.
Look through your code and try to find a place where such situation might occur (for instance, do you access self.values from other classes?). Unfortunately, I wasn't able to find such place in several minutes. If you said upon which collection enumeration this error occurs, it would help).
UPDATE:
P.S. I just thought that the error might be related to the saveMainContext function. It is performed right before a call to saved. saveMainContext is performed on the background thread (in the original code, I mean), and saved is performed on the main thread. So after fixing saveMainContext, the error might go away (I'm not 100% sure, though).
You are violating thread confinement.
You cannot write to CoreData in Background, and read in MainThread.
All operation on CoreData must be done in the same thread
I have preloaded data from a .csv file into coredata. I am fetching the data in the following way
var places:[Places] = []
in viewDidLoad :
if let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext {
let fetchRequest = NSFetchRequest(entityName: "Places")
do{
places = try managedObjectContext.executeFetchRequest(fetchRequest) as! [Places]
}
catch let error as NSError{
print("Failed to retrieve record: \(error.localizedDescription)")
}
}
In the data there is an attribute isFavorite of type String whose initial value is false. I am changing the value of isFavorite on button click. I want to save the changes made by the user. How can i make this change persistent ?
Here is my button action
#IBAction func addToFavourites(sender: AnyObject) {
cell = tableView.cellForRowAtIndexPath(NSIndexPath(forRow: sender.tag, inSection: 0)) as! CustomTableViewCell
if cell.isFavouriteLabel.text! == "false" {
cell.isFavouriteLabel.text = "true"
}else if cell.isFavouriteLabel.text == "true"{
cell.isFavouriteLabel.text = "false"
}
}
Basically i want to set the value of places.isFavourite = cell.isFavoriteLabel.text and save to core data
EDIT : if i try this inside my button action method
if let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext {
let place : Places = Places()
place.isFavourite = cell.isFavouriteLabel.text
do{
try managedObjectContext.save()
} catch let error as NSError{
print(error)
}
}
i am getting an error : Failed to call designated initializer on NSManagedObject class
if i simply add this code in the button action method
places.isFavourite = cell.isFavouriteLabel.text
i get this error : [Places] does not have a member named isFavourite
Your current code is:
if let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext {
let place : Places = Places()
place.isFavourite = cell.isFavouriteLabel.text
do{
try managedObjectContext.save()
} catch let error as NSError{
print(error)
}
}
That would create a new place (if it worked), but you need to update an existing one.
You have the places returned from managedObjectContext.executeFetchRequest.
So you need to get something like places[index_of_the_cell_in_question].isFavourite = cell.isFavouriteLabel.text
and then managedObjectContext.save().
Use the save function of the NSManagedObjectContext:
places.isFavourite = cell.isFavoriteLabel.text
var error: NSError?
if managedObjectContext.save(&error) != true {
// Error
}
This is simple as this:
Find the entry you want to modify in places then save the core data context.
func saveContext () {
if let moc = self.managedObjectContext {
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
println("Unresolved error \(error), \(error!.userInfo)")
abort()
}
}
}
I suggest you used a manager to insert, fetch and delete entry in your core data.
import Foundation
import CoreData
class CoreDataHelper: NSObject {
class var shareInstance:CoreDataHelper {
struct Static {
static let instance:CoreDataHelper = CoreDataHelper()
}
return Static.instance
}
//MARK: - Insert -
func insertEntityForName(entityName:String) -> AnyObject {
return NSEntityDescription.insertNewObjectForEntityForName(entityName, inManagedObjectContext: self.managedObjectContext!)
}
//MARK: - Fetch -
func fetchEntitiesForName(entityName:String) -> NSArray {
...
}
//MARK: - Delete -
func deleteObject(object:NSManagedObject) {
self.managedObjectContext!.deleteObject(object)
}
// MARK: - Core Data Saving support -
func saveContext () {
if let moc = self.managedObjectContext {
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
println("Unresolved error \(error), \(error!.userInfo)")
abort()
}
}
}
Hop this can help you
I am trying to follow this tutorial in order to save the Local Cache of UIWebView in my app.
I had to convert a few lines to swift 2 but i cannot find the way to solve the issue when add to NSManagedObjectContext save an argument of type NSError.
from the picture you can understand better what I mean.
How could I fix this?
The code I'm using is:
func saveCachedResponse () {
print("Saving cached response")
// 1
let delegate = UIApplication.sharedApplication().delegate as! AppDelegate
let context = delegate.managedObjectContext!
// 2
let cachedResponse = NSEntityDescription.insertNewObjectForEntityForName("CachedURLResponse", inManagedObjectContext: context) as NSManagedObject
cachedResponse.setValue(self.mutableData, forKey: "data")
cachedResponse.setValue(self.request.URL!.absoluteString, forKey: "url")
cachedResponse.setValue(NSDate(), forKey: "timestamp")
cachedResponse.setValue(self.response.MIMEType, forKey: "mimeType")
cachedResponse.setValue(self.response.textEncodingName, forKey: "encoding")
// 3
var error: NSError?
let success = context.save(&error)
if !success {
print("Could not cache the response")
}
}
Surface Error
Handle print("Could not cache the response") not listed in the other answers:
do {
try context.save()
} catch let error {
print("Could not cache the response \(error)")
}
Avoid DB corruption, use perform block for all MOC access
As I like code examples to be somewhat robust, here is a more exhaustive solution:
func saveCachedResponse (context: NSManagedObjectContext) {
context.performBlockAndWait({ () -> Void in
let cachedResponse = NSEntityDescription.insertNewObjectForEntityForName("CachedURLResponse", inManagedObjectContext: context) as NSManagedObject
cachedResponse.setValue(self.mutableData, forKey: "data")
// etc.
do {
try context.save()
} catch let error {
print("Could not cache the response \(error)")
}
})
}
In Swift 2.0
To save context, you have to use do { try ...} and catch {...} your error.
// Save the context.
do {
try context.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
//print("Unresolved error \(error), \(error.userInfo)")
}
Edit
let entity = NSEntityDescription.entityForName("CachedURLResponse", inManagedObjectContext: context)
let newCacheUrl = NSEntityDescription.insertNewObjectForEntityForName(entity.name!, inManagedObjectContext: context)
newCacheUrl.setValue(NSDate(), forKey: "timeStamp")
I use something like this with Xcode 7 and I have not fatal error.
do {
try managedObjectContext.save()
} catch let error as NSError
{
NSLog("Unresolved error \(error), \(error.userInfo)")
}
do {
let success = try context.save()
} catch {
}
will do the trick. The error got nothing to do Xcode 7.