Я работал с Core Data в приложении для iPad и могу успешно сохранять и извлекать данные из приложения.Однако, когда вы полностью закрываете приложение, полностью выходите, вынимаете его из многозадачности, и эти данные исчезают.
Так в любом случае Core Data хранит эти данные где-нибудь, когда приложение закрыто?Или мне нужно искать где-то еще?
РЕДАКТИРОВАТЬ: Это в делегате приложения didFinishLaunchingWithOptions: [[[UIApplication sharedApplication] delegate] managedObjectContext];, а затем у меня есть это: context_ = [(prototypeAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; в подклассе UIView.
Это код NSPersistentStoreCoordinator, предварительно созданный в делегате приложения:
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
if (persistentStoreCoordinator_ != nil) {
return persistentStoreCoordinator_;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"prototype.sqlite"];
NSError *error = nil;
persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![persistentStoreCoordinator_ addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
Typical reasons for an error here include:
* The persistent store is not accessible;
* The schema for the persistent store is incompatible with current managed object model.
Check the error message to determine what the actual problem was.
If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.
If you encounter schema incompatibility errors during development, you can reduce their frequency by:
* Simply deleting the existing store:
[[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]
* Performing automatic lightweight migration by passing the following dictionary as the options parameter:
[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.
*/
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return persistentStoreCoordinator_;
}
Пока я использую это для извлечения данных:
NSFetchRequest *fetch = [[NSFetchRequest alloc] init];
NSEntityDescription *testEntity = [NSEntityDescription entityForName:@"DatedText" inManagedObjectContext:context_];
[fetch setEntity:testEntity];
NSPredicate *pred = [NSPredicate predicateWithFormat:@"dateSaved == %@", datePicker.date];
[fetch setPredicate:pred];
NSError *fetchError = nil;
NSArray *fetchedObjs = [context_ executeFetchRequest:fetch error:&fetchError];
if (fetchError != nil) {
NSLog(@"fetchError = %@, details = %@",fetchError,fetchError.userInfo);
}
noteTextView.text = [[fetchedObjs objectAtIndex:0] valueForKey:@"savedText"];
И это для сохранения данных:
NSManagedObject *newDatedText;
newDatedText = [NSEntityDescription insertNewObjectForEntityForName:@"DatedText" inManagedObjectContext:context_];
[newDatedText setValue:noteTextView.text forKey:@"savedText"];
[newDatedText setValue:datePicker.date forKey:@"dateSaved"];
NSError *saveError = nil;
[context_ save:&saveError];
if (saveError != nil) {
NSLog(@"[%@ saveContext] Error saving context: Error = %@, details = %@",[self class], saveError,saveError.userInfo);
}