Delete/Reset all entries in Core Data?

Question

Do you know of any way to delete all of the entries stored in Core Data? My schema should stay the same; I just want to reset it to blank.

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Edit

I'm looking to do this programmatically so that a user can essentially hit a reset button.

Answer 1

Delete the persistent store file and setup a new persistent store coordinator?

Answer 2

You can delete the SQLite file - but I choose to do it by purging the tables individually with a functions:

- (void) deleteAllObjects: (NSString *) entityDescription  {
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:entityDescription inManagedObjectContext:_managedObjectContext];
    [fetchRequest setEntity:entity];

    NSError *error;
    NSArray *items = [_managedObjectContext executeFetchRequest:fetchRequest error:&error];
    [fetchRequest release];


    for (NSManagedObject *managedObject in items) {
        [_managedObjectContext deleteObject:managedObject];
        DLog(@"%@ object deleted",entityDescription);
    }
    if (![_managedObjectContext save:&error]) {
        DLog(@"Error deleting %@ - error:%@",entityDescription,error);
    }

}

The reason I chose to do it table by table is that it makes me confirm as I am doing the programming that deleting the contents of the table is sensible and there is not data that I would rather keep.

Doing it this will is much slower than just deleting the file and I will change to a file delete if I this method takes too long.

Answer 3

You can still delete the file programmatically, using the NSFileManager:removeItemAtPath:: method.

NSPersistentStore *store = ...;
NSError *error;
NSURL *storeURL = store.URL;
NSPersistentStoreCoordinator *storeCoordinator = ...;
[storeCoordinator removePersistentStore:store error:&error];
[[NSFileManager defaultManager] removeItemAtPath:storeURL.path error:&error];

Then, just add the persistent store back to ensure it is recreated properly.

The programmatic way for iterating through each entity is both slower and prone to error. The use for doing it that way is if you want to delete some entities and not others. However you still need to make sure you retain referential integrity or you won't be able to persist your changes.

Just removing the store and recreating it is both fast and safe, and can certainly be done programatically at runtime.

Update for iOS5+

With the introduction of external binary storage (allowsExternalBinaryDataStorage or Store in External Record File) in iOS 5 and OS X 10.7, simply deleting files pointed by storeURLs is not enough. You'll leave the external record files behind. Since the naming scheme of these external record files is not public, I don't have a universal solution yet. – an0 May 8 '12 at 23:00

Answer 4

Several good answers to this question. Here's a nice concise one. The first two lines delete the sqlite database. Then the for: loop deletes any objects in the managedObjectContext memory.

NSURL *storeURL = [[(FXYAppDelegate*)[[UIApplication sharedApplication] delegate] applicationDocumentsDirectory] URLByAppendingPathComponent:@"AppName.sqlite"];
[[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil];
for (NSManagedObject *ct in [self.managedObjectContext registeredObjects]) {
    [self.managedObjectContext deleteObject:ct];
}

Answer 5

you can also find all the entity names, and delete them by name. Its a longer version but works well, that way you dont have to work with persistence store

 - (void)clearCoreData
{
NSError *error;
NSEntityDescription *des = [NSEntityDescription entityForName:@"Any_Entity_Name" inManagedObjectContext:_managedObjectContext];
NSManagedObjectModel *model = [des managedObjectModel];
NSArray *entityNames = [[model entities] valueForKey:@"name"];

for (NSString *entityName in entityNames){

    NSFetchRequest *deleteAll = [NSFetchRequest fetchRequestWithEntityName:entityName];
    NSArray *matches = [self.database.managedObjectContext executeFetchRequest:deleteAll error:&error];

}
    if (matches.count > 0){
        for (id obj in matches){

            [_managedObjectContext deleteObject:obj];
        }
       [self.database.managedObjectContext save:&error];
    }
}

for "Any_Entity_Name" just give any one of your entity's name, we only need to figure out the entity description your entities are within. ValueForKey@"name" will return all the entity names. Finally, dont forget to save.

Answer 6

Assuming you are using MagicalRecord and have a default persistence store:

I don't like all the solutions that assume certain files to exist and/or demand entering the entities names or classes. This is a Swift(2), safe way to delete all the data from all the entities. After deleting it will recreate a fresh stack too (I am actually not sure as to how neccessery this part is).

It's godo for "logout" style situations when you want to delete everything but have a working store and moc to get new data in (once the user logs in...)

extension NSManagedObject {

    class func dropAllData() {

        MagicalRecord.saveWithBlock({ context in

            for name in NSManagedObjectModel.MR_defaultManagedObjectModel().entitiesByName.keys {
                do { try self.deleteAll(name, context: context) }
                catch { print("⚠️ ✏️ Error when deleting \(name): \(error)") }
            }

            }) { done, err in
                MagicalRecord.cleanUp()
                MagicalRecord.setupCoreDataStackWithStoreNamed("myStoreName")
        }
    }

    private class func deleteAll(name: String, context ctx: NSManagedObjectContext) throws {
        let all = NSFetchRequest(entityName: name)
        all.includesPropertyValues = false

        let allObjs = try ctx.executeFetchRequest(all)
        for obj in allObjs {
            obj.MR_deleteEntityInContext(ctx)
        }

    }
}