Delete Data from Coredata Swift

Question

In my tableViewController I have the following. And I am trying to get delete an item to work.

var myData: Array = []

override func tableV         


        

Answer 1

To complete the answer from zisoft:

You need to save your context after deleting an object.

So the correct way would be:

// get your app managemenent context

let appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
let context = self.appDel.managedObjectContext!

// remove your object

context.del(data)

// save your changes 
context.save(nil)

Note to check first if there are any delete rules (if you have any related objects)

Answer 2

None of the answers above helped me in the case that I'm using Core Data with a FetchedResultsController for a tableView. As such here is my implementation to handle deleting below. My example uses a simple example assuming you want to delete a picture from swiping left on a table and selecting the default delete option.

Swift 3 Solution for FetchedResultsController Implementaitons

First add this delegate method for the table view to allow editing when you swipe on the row.

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {

        if editingStyle == .delete {
            print("editing style delete detected")

            let context = DataController.sharedInstance().managedObjectContext

            let picture = self.fetchedResultsController.object(at: indexPath) as Pictures
            context.delete(picture)

            //Actually remove picture from storage on the device.
            let fileManager = FileManager.default
            let imagefilepath = "\(AppDelegate.appDelegate.applicationDocumentsDirectory())/\(picture.filepath!)"

            do {
                try fileManager.removeItem(atPath: imagefilepath)
            }
            catch let error as NSError {
                print("Ooops! Something went wrong while trying to delete picture file: \(error)")
            }

            //Save the context change.
            AppDelegate.appDelegate.saveContext()

            tableView.reloadData()//update changes

        }
    }

Once you've done this, make sure the fetchedResultsController has its delegate set to your controller and implement these methods.

    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
        switch(type){
            case .insert:
                break;
            case .delete:
                print("delete detected on FRC Delegate")
                tableView.deleteRows(at: [indexPath!], with: .fade)
                break;
            case .update:
                break;
            case .move:
                break;
        }
    }

The secret here is getting access to the object via the fetchedResultsController.object method

let picture = self.fetchedResultsController.object(at: indexPath) as Pictures

This way you can run

context.delete(picture)

which is smart about deleting NSManagedObjects.

Extra Info Related to my Implementation (Only read below if you are needing more details)

---------------------------------------------------------------------------

Picture+CoreDataProperties.swift

import Foundation
import CoreData


extension Pictures {

    @nonobjc public class func fetchRequest() -> NSFetchRequest<Pictures> {
        return NSFetchRequest<Pictures>(entityName: "Pictures");
    }

    @NSManaged public var date: NSDate?
    @NSManaged public var desc: String?
    @NSManaged public var filepath: String?
    @NSManaged public var type: String?
    @NSManaged public var workorder: Workorders?

}

Pictures+CoreDataClass.swift

import Foundation
import CoreData


public class Pictures: NSManagedObject {

}

The file below is my coreData stack handler.

DataController.swift

import UIKit
import CoreData

    class DataController: NSObject {

    var managedObjectContext: NSManagedObjectContext
    static var dataController: DataController!

    override init() {
        // This resource is the same name as your xcdatamodeld contained in your project.
        guard let modelURL = Bundle.main.url(forResource: "WorkOrders", withExtension: "momd") else {
            fatalError("Error loading model from bundle")
        }

        // The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
        guard let mom = NSManagedObjectModel(contentsOf: modelURL) else {
            fatalError("Error initializing mom from: \(modelURL)")
        }

        let psc = NSPersistentStoreCoordinator(managedObjectModel: mom)

        managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
        managedObjectContext.persistentStoreCoordinator = psc

        let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        let docURL = urls[urls.endIndex-1]
        /* The directory the application uses to store the Core Data store file.
         This code uses a file named "DataModel.sqlite" in the application's documents directory.
         */
        let storeURL = docURL.appendingPathComponent("WorkOrders.sqlite")
        do {
            let options = [NSSQLitePragmasOption: ["journal_mode": "DELETE"]]
            try psc.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: storeURL, options: options)
        } catch {
            fatalError("Error migrating store: \(error)")
        }

    }

    class func sharedInstance() -> DataController {

        if (dataController != nil) {
            return dataController
        }

        dataController = DataController()

        return dataController
    }
}

This is where my save method is for saving the context.

AppDelegate.swift

import UIKit
import CoreData

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    static var appDelegate: AppDelegate!

    /// Returns application documents directory path
    ///
    /// - returns: application documents directory path string
    func applicationDocumentsDirectory() -> String {
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        print(paths[0])
        return paths[0]
    }

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        //Override point for customization after application launch.

        AppDelegate.appDelegate = self
        _ = applicationDocumentsDirectory();

        return true
    }

    func applicationWillResignActive(_ application: UIApplication) {
        // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
        // Use this method to pause ongoing tasks, disable timers, and invalidate graphics rendering callbacks. Games should use this method to pause the game.
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
        // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
        // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
        // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
        // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
    }

    func applicationWillTerminate(_ application: UIApplication) {
        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
        // Saves changes in the application's managed object context before the application terminates.
        self.saveContext()
    }

    // 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: "WorkOrders")
        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
    }()

    // MARK: - Core Data Saving support

    func saveContext () {
        let context = DataController.sharedInstance().managedObjectContext
        context.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        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)")
            }
        }
    }

}

Answer 3

let entityDescription =
    NSEntityDescription.entity(forEntityName: "Contacts",
                               in: managedObjectContext)
let request: NSFetchRequest<Contacts> = Contacts.fetchRequest()
request.entity = entityDescription
if let result = try? managedObjectContext.fetch(request) {
    for object in result {
        do {
            try managedObjectContext.delete(object)
            txtName?.text = ""
            txtAddress?.text = ""
            txtPhone?.text = ""
            Status?.text = "Contact Deleted"
            txtName?.text = ""

        }
        catch let error {
            Status?.text = error.localizedDescription
        }
    }
}

Answer 4

SWIFT 5

func removeCoreData() {
    guard let appDelegate =
      UIApplication.shared.delegate as? AppDelegate else {
        return
    }
    let managedContext = appDelegate.persistentContainer.viewContext
    let fetchRequest: NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "YourEntityName") // Find this name in your .xcdatamodeld file
    let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
    
    do {
        try managedContext.execute(deleteRequest)
    } catch let error as NSError {
        // TODO: handle the error
        print(error.localizedDescription)
    }
}

This completely deletes all of your data that is stored in the specified entity.

Answer 5

Swift 3.0

Below is the code to delete item and to reload the data.

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {

     let noteEntity = "Note" //Entity Name

     let managedContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

     let note = notes[indexPath.row]

     if editingStyle == .delete {
        managedContext.delete(note)

        do {
            try managedContext.save()
        } catch let error as NSError {
            print("Error While Deleting Note: \(error.userInfo)")
        }

     }

    //Code to Fetch New Data From The DB and Reload Table.
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: noteEntity)

    do {
        notes = try managedContext.fetch(fetchRequest) as! [Note]
    } catch let error as NSError {
        print("Error While Fetching Data From DB: \(error.userInfo)")
    }
    noteTableView.reloadData()
}

Answer 6

For Xcode 8 and Swift 3.0. If we need to DELETE all data from any Table than we should use the code:

LoadStorage Class file: it also support iOS 9 and iOS 10 above.

import UIKit
import CoreData

class localStorage: NSObject {

    //MARK: - Up for iOS10 and above

    @available(iOS 10.0, *)
    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: "JJS_Connect")
    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
}()


// MARK: - Core Data Saving support
func saveContext () {
    if #available(iOS 10.0, *) {
        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)")
        }
    }
}
else {

}

}


            //MARK: - Usp for iOS10 below
            lazy var applicationDocumentsDirectory: NSURL = {
                // The directory the application uses to store the Core Data store file. This code uses a directory named "com.razeware.HitList" in the application's documents Application Support directory.
                let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
                return urls[urls.count-1] as NSURL
            }()

            lazy var managedObjectModel: NSManagedObjectModel = {
                // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
                let modelURL = Bundle.main.url(forResource: "JJS_Connect", withExtension: "momd")!
                return NSManagedObjectModel(contentsOf: modelURL)!
            }()

            lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
                // The persistent store coordinator for the application. This implementation creates and return a coordinator, having added 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.
                // Create the coordinator and store
                let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
                let url = self.applicationDocumentsDirectory.appendingPathComponent("JJS_Connect.sqlite")
                var failureReason = "There was an error creating or loading the application's saved data."
                do {
                    try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: nil)
                } 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)")
                    abort()
                }

                return coordinator
            }()

            lazy var managedObjectContext: NSManagedObjectContext = {
                // 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
                var managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
                managedObjectContext.persistentStoreCoordinator = coordinator
                return managedObjectContext
            }()


            // MARK: - Creating NSManagedObject for saving data into table
            func getContext() -> NSManagedObjectContext {
                if #available(iOS 10.0, *) {
                    let context = self.persistentContainer.viewContext
                    return context

                }else{
                    let context = self.managedObjectContext
                    return context
                }
            }
        }

Than Create DatabaseMaster class and make function:

    //MARK: - DELETE OPERATION FROM DB
        func deleteFromAddressMaster() -> Void{
            let request: NSFetchRequest<Address_master>
            if #available(iOS 10.0, OSX 10.12, *) {
                request = Address_master.fetchRequest()
            } else {
                request = NSFetchRequest(entityName: "Address_master")
            }

            do {
                let results = try localStr.getContext().fetch(request)
                    for address in results {
                        print(" Deleted... \(address.group_id)")
                        localStr.getContext().delete(address)
                    }

            } catch let error {
                print(error.localizedDescription)
            }
        }

Address_master is Subclass file name. please define

let localStr = localStorage()

in DatabasMaster Class file.