Swift 3 Core Data Delete Object

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?)

Solution 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.

Solution 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.

Solution 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")
    }
}

Solution 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
} 

Solution 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")
     }

View more solutions