iOS: Delete ALL Core Data Swift

Question

I am a little confused as to how to delete all core data in swift. I have created a button with an IBAction linked. On the click of the button I have the follow

Answer 1

Swift 5.1

let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)

        do {
            try coreDataManager.managedObjectContext.execute(batchDeleteRequest)
        } catch {
            print("Detele all data in \(entityName) error :", error)
        }

Answer 2

To Delete all data you can use NSBatchDeleteRequest

func deleteAllData(entity: String)
{
    let ReqVar = NSFetchRequest(entityName: entity)
    let DelAllReqVar = NSBatchDeleteRequest(fetchRequest: ReqVar)
    do { try ContxtVar.executeRequest(DelAllReqVar) }
    catch { print(error) }
}

Answer 3

This clean() method will fetch entities list from DataModel and clear all data.

func deleteAll(entityName: String) -> Error? {
            if #available(iOS 9.0, *) {
                do {
                    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
                    let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
                    try context.execute(batchDeleteRequest)
                } catch {
                    return error
                }
                return nil
            } else {
                let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
                fetchRequest.returnsObjectsAsFaults = false
                do
                {
                    let results = try context.fetch(fetchRequest)
                    for managedObject in results
                    {
                        if let managedObjectData:NSManagedObject = managedObject as? NSManagedObject {
                            context.delete(managedObjectData)
                        }
                    }
                } catch  {
                    return error
                }
                return nil
            }
        }

        var objectModel: NSManagedObjectModel? {
            if #available(iOS 10.0, *) {
                return persistentContainer.managedObjectModel
            } else {
                return persistentStoreCoordinator?.managedObjectModel
            }
        }

        open func clean() {
            if let models = objectModel?.entities {
                for entity in models {
                    if let entityName = entity.name {
                        _ = deleteAll(entityName: entityName)
                    }
                }
            }
        }

Happy Coding!

Answer 4

You can use destroyPersistentStore starting in iOS 9.0 and Swift 3:

public func clearDatabase() {
    guard let url = persistentContainer.persistentStoreDescriptions.first?.url else { return }

    let persistentStoreCoordinator = persistentContainer.persistentStoreCoordinator

     do {
         try persistentStoreCoordinator.destroyPersistentStore(at:url!, ofType: NSSQLiteStoreType, options: nil)
         try persistentStoreCoordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url!, options: nil)
    } catch let error {
         print("Attempted to clear persistent store: " + error.localizedDescription)
        }
    }
}

Answer 5

Swift 5.1

Most of the posts here suggests to create a function to delete all entities by name and then delete all your entities by name. like so :

resetEntity(named: "MyEntity1")
resetEntity(named: "MyEntity2")
resetEntity(named: "MyEntity3")
...

But if the real question is how to clean ALL CoreData entity in one go, I suggest you loop over entity names:

// Supposing this is a CoreDataController/CoreDataStack class where you have access to `viewContext` and `persistantContainer`
// Otherwise just pass the `persistantContainer` as a parameter, from which you can also retrieve the `viewContext` 
func resetAllCoreData() {

     // get all entities and loop over them
     let entityNames = self.persistentContainer.managedObjectModel.entities.map({ $0.name!})
     entityNames.forEach { [weak self] entityName in   
        let deleteFetch = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        let deleteRequest = NSBatchDeleteRequest(fetchRequest: deleteFetch)

        do {
            try self?.context.execute(deleteRequest)
            try self?.context.save()
        } catch {
            // error
        }
    }
}

Hope this can help

Answer 6

There are two simple methods as far as i know , first

Method 1:

Fetch, Delete, Repeat

// Initialize Fetch Request

let fetchRequest = NSFetchRequest(entityName: "Item")

// Configure Fetch Request

 fetchRequest.includesPropertyValues = false

do {

let items = try managedObjectContext.executeFetchRequest(fetchRequest) as! [NSManagedObject]

for item in items {
    managedObjectContext.deleteObject(item)
}

// Save Changes
try managedObjectContext.save()

} catch {
// Error Handling
// ...

}

Methode 2:

Batch Delete Request

// Create Fetch Request

let fetchRequest = NSFetchRequest(entityName: "Item")

// Create Batch Delete Request

     let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
       do {
          try managedObjectContext.executeRequest(batchDeleteRequest)

          } catch {
// Error Handling
    }

I have tested both and they both work fine