iOS: Delete ALL Core Data Swift

Try this simple solution:

func deleteAllData(entity: String)
{
    let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
    let managedContext = appDelegate.managedObjectContext
    let fetchRequest = NSFetchRequest(entityName: entity)
    fetchRequest.returnsObjectsAsFaults = false

    do 
    {
        let results = try managedContext.executeFetchRequest(fetchRequest)
        for managedObject in results
        {
            let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
            managedContext.deleteObject(managedObjectData)
        }
    } catch let error as NSError {
        print("Detele all data in \(entity) error : \(error) \(error.userInfo)")
    }
}

Swift 4

func deleteAllData(_ entity:String) {
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entity)
    fetchRequest.returnsObjectsAsFaults = false
    do {
        let results = try dataController.viewContext.fetch(fetchRequest)
        for object in results {
            guard let objectData = object as? NSManagedObject else {continue}
            dataController.viewContext.delete(objectData)
        }
    } catch let error {
        print("Detele all data in \(entity) error :", error)
    }
}

Implementation:

 self.deleteAllData("your_entityName")