Swift 3 Core Data Delete Object - ios

Question

Unfortunately the new Core Data semantics make me crazy. My previous question had a clean code that didn't work because of incorrect auto generation of header files. Now I continue my work with deleting objects.
My code seems to be very simple:
func deleteProfile(withID: Int) {
let fetchRequest: NSFetchRequest<Profile> = Profile.fetchRequest()
fetchRequest.predicate = Predicate.init(format: "profileID==\(withID)")
let object = try! context.fetch(fetchRequest)
context.delete(object)
}
I did a "hard" debug with print(object) instead of context.delete(object) and it showed me the right object.
So I need just to delete it.
P.S. there is no deleteObject. Now NSManagedContext has only public func delete(_ sender: AnyObject?)

Answer 1

The result of a fetch is an array of managed objects, in your case
[Event], so you can enumerate the array and delete all matching objects.
Example (using try? instead of try! to avoid a crash in the case
of a fetch error):
if let result = try? context.fetch(fetchRequest) {
for object in result {
context.delete(object)
}
}
do {
try context.save()
} catch {
//Handle error
}
If no matching objects exist then the fetch succeeds, but the resulting
array is empty.
Note: In your code, object has the type [Event] and therefore in
context.delete(object)
the compiler creates a call to the
public func delete(_ sender: AnyObject?)
method of NSObject instead of the expected
public func delete(_ object: NSManagedObject)
method of NSManagedObjectContext. That is why your code compiles
but fails at runtime.

Answer 2

The trick here, it is save context after deleting your objects.
let fetchRequest: NSFetchRequest<Profile> = Profile.fetchRequest()
fetchRequest.predicate = Predicate.init(format: "profileID==\(withID)")
let objects = try! context.fetch(fetchRequest)
for obj in objects {
context.delete(obj)
}
do {
try context.save() // <- remember to put this :)
} catch {
// Do something... fatalerror
}
I hope this can help someone.

Answer 3

func deleteRecords() {
let delegate = UIApplication.shared.delegate as! AppDelegate
let context = delegate.persistentContainer.viewContext
let deleteFetch = NSFetchRequest<NSFetchRequestResult>(entityName: "nameofentity")
let deleteRequest = NSBatchDeleteRequest(fetchRequest: deleteFetch)
do {
try context.execute(deleteRequest)
try context.save()
} catch {
print ("There was an error")
}
}

Answer 4

Delete core data objects swift 3
// MARK: Delete Data Records
func deleteRecords() -> Void {
let moc = getContext()
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Person")
let result = try? moc.fetch(fetchRequest)
let resultData = result as! [Person]
for object in resultData {
moc.delete(object)
}
do {
try moc.save()
print("saved!")
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
} catch {
}
}
// MARK: Get Context
func getContext () -> NSManagedObjectContext {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
return appDelegate.persistentContainer.viewContext
}

Answer 5

Swift 4.1, 4.2 and 5.0
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let requestDel = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")
requestDel.returnsObjectsAsFaults = false
// If you want to delete data on basis of some condition then you can use NSPredicate
// let predicateDel = NSPredicate(format: "age > %d", argumentArray: [10])
// requestDel.predicate = predicateDel
do {
let arrUsrObj = try context.fetch(requestDel)
for usrObj in arrUsrObj as! [NSManagedObject] { // Fetching Object
context.delete(usrObj) // Deleting Object
}
} catch {
print("Failed")
}
// Saving the Delete operation
do {
try context.save()
} catch {
print("Failed saving")
}

Answer 6

Swift 4 without using string for Entity
let fetchRequest: NSFetchRequest<Profile> = Profile.fetchRequest()
fetchRequest.predicate = Predicate.init(format: "profileID==\(withID)")
do {
let objects = try context.fetch(fetchRequest)
for object in objects {
context.delete(object)
}
try context.save()
} catch _ {
// error handling
}

Answer 7

Delete Core Data Object with query in Swift 5, 4.2
let fetchRequest = NSFetchRequest<Your_Model>(entityName: "Your_Entity_Name")
fetchRequest.predicate = NSPredicate(format: "any your_key == %d", your_value)
hope this will help to someone

Answer 8

Swift 5
Common function for Deleting core data objects for any anity swift 5
func deleteEntityObjectByKeyValue<T>(className: T.Type, key: String, value: Any) -> Bool {
let context = CoreDataStack.sharedStack.mainContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: String(describing: className.self))
//Search based on data type.I used for Int and String
if let sValue = value as? String {
let predicate = NSPredicate(format: "\(key) == %#", sValue)
fetchRequest.predicate = predicate
} else if let iValue = value as? Int64 {
let predicate = NSPredicate(format: "\(key) == %d", iValue)
fetchRequest.predicate = predicate
}
do {
let result = try context.fetch(fetchRequest)
if result.count != 0 {
if let managedObject = result[0] as? NSManagedObject {
context.delete(managedObject)
do {
try context.save()
return true
}
catch let error {
print(error.localizedDescription)
}
}
}
return false
} catch let error {
print(error.localizedDescription)
}
return false
}
How To Use it:
let isSaved = CoreDataOperations.shared.deleteEntityObjectByKeyValue(className: EmpolyeeData.self, key: "employeeId", value:1234)
If isSaved {
print("Deleted obj Successfully")
}

Answer 9

Swift 4,5
It is useful to delete particular record or all records from entity.
1.Create a NSPersistentContainer and NSManagedObjectContext using below code.
class CoreDataStack: NSObject {
static var sharedStack = CoreDataStack()
private override init() {}
lazy var persistentContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: "Employee")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let url = storeDescription.url {
print("SQLITE STORE LOCATION: \(url.absoluteString)")
}
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
container.viewContext.shouldDeleteInaccessibleFaults = true
container.viewContext.automaticallyMergesChangesFromParent = true
return container
}()
private lazy var applicationDocumentsDirectory: URL = {
let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
return urls[urls.count-1]
}()
private lazy var managedObjectModel: NSManagedObjectModel = {
let modelURL = Bundle.main.url(forResource: "____", withExtension: "____")!
return NSManagedObjectModel(contentsOf: modelURL)!
}()
public lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.appendingPathComponent("Employee" + ".sqlite")
var failureReason = "There was an error creating or loading the application's saved data."
do {
let options = [ NSMigratePersistentStoresAutomaticallyOption : true, NSInferMappingModelAutomaticallyOption : true ]
try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: options)
} catch {
// Report any error we got.
var dict = [String: AnyObject]()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" as AnyObject?
dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject?
dict[NSUnderlyingErrorKey] = error as NSError
let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
// Replace this 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.
NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
}
return coordinator
}()
lazy var mainContext: NSManagedObjectContext = {
var managedObjectContext: NSManagedObjectContext?
if #available(iOS 10.0, *){
managedObjectContext = self.persistentContainer.viewContext
managedObjectContext?.mergePolicy = NSMergePolicy.init(merge: NSMergePolicyType.mergeByPropertyObjectTrumpMergePolicyType)
}
else{
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
let coordinator = self.persistentStoreCoordinator
managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
managedObjectContext?.persistentStoreCoordinator = coordinator
managedObjectContext?.mergePolicy = NSMergePolicy.init(merge: NSMergePolicyType.mergeByPropertyObjectTrumpMergePolicyType)
}
return managedObjectContext!
}()
}
2.Common function for Deleting core data all objects for any Entity swift 5
func deleteEntityData(entity : String) {
let deleteFetch = NSFetchRequest<NSFetchRequestResult>(entityName: entity)
let deleteRequest = NSBatchDeleteRequest(fetchRequest: deleteFetch)
do {
try CoreDataStack.sharedStack.mainContext.execute(deleteRequest)
CoreDataStack.sharedStack.saveMainContext()
} catch {
print ("There was an error")
}
}
3.How to use above code.
self.deleteEntityData(entity : "Employee")
4.If you want to delete Particular object from Entity
func deleteEntityObjectByKeyValue<T>(entityName: T.Type, key: String, value: Any) -> Bool {
let context = CoreDataStack.sharedStack.mainContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: String(describing: entityName.self))
if let sValue = value as? String {
let predicate = NSPredicate(format: "\(key) == %#", sValue)
fetchRequest.predicate = predicate
} else if let iValue = value as? Int64 {
let predicate = NSPredicate(format: "\(key) == %d", iValue)
fetchRequest.predicate = predicate
}
do {
let result = try context.fetch(fetchRequest)
if result.count != 0 {
if let managedObject = result[0] as? NSManagedObject {
context.delete(managedObject)
do {
CoreDataStack.sharedStack.saveMainContext()
return true
}
catch let error {
print(error.localizedDescription)
}
}
}
return false
} catch let error {
print(error.localizedDescription)
}
return false
}

Answer 10

Delete the object from core data
let entity = NSEntityDescription.entity(forEntityName: "Students", in: managedContext)
let request = NSFetchRequest<NSFetchRequestResult>()
request.entity = entity
if let result = try? managedContext.fetch(request) {
for object in result {
managedContext.delete(object as! NSManagedObject)
}
txtName.text = ""
txtPhone.text = ""
txt_Address.text = ""
labelStatus.text = "Deleted"
}