This feels strange and I somehow could not find an answer through search. This is an issue on Xcode iOS Simulator.
I am write an data persistence code. When instantiate the data store, I pretty much copied the following code fragment from Apple (https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreData/InitializingtheCoreDataStack.html#//apple_ref/doc/uid/TP40001075-CH4-SW1).
Now, the issue seems - storeURL (when in debugging) is a URL containing a long numeric string and when relaunching the simulator, that long numeric string was changed. So the sqlite file is not reachable any more. I do believe I saved the data correctly because I debugged through the code (and context save api called with no error), I retrieved data after saving (without relaunching) and I see the data using command line sqlite tool against the sqlite file.
import UIKit
import CoreData
class DataController: NSObject {
var managedObjectContext: NSManagedObjectContext
init() {
// This resource is the same name as your xcdatamodeld contained in your project.
guard let modelURL = NSBundle.mainBundle().URLForResource("DataModel", 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(contentsOfURL: modelURL) else {
fatalError("Error initializing mom from: \(modelURL)")
}
let psc = NSPersistentStoreCoordinator(managedObjectModel: mom)
self.managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
self.managedObjectContext.persistentStoreCoordinator = psc
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0)) {
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .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.URLByAppendingPathComponent("DataModel.sqlite")
do {
try psc.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: storeURL, options: nil)
} catch {
fatalError("Error migrating store: \(error)")
}
}
}
}
iosiphoneswiftios-simulatorxcode7
This is what basically Matt said in the comment section. This issue is related to where to place the .sqlite file.