核心数据。 不通过应用程序终止持续存在

Question

So, i finally got Core Data to work as intended. Saving stuff, and loading it within a UITableView subclass. Works perfectly as long as the application is running or in the background.

But as soon as the app is terminated (not uninstalled), and reopened, the data seems lost, or rather reset to nothing(when i load the NSManagedObjects to my array, i still get the correct amount - the properties are just nil)...

I save the context in:

- (void)applicationDidEnterBackground:(UIApplication *)application

Besides that, the App-Delegate is 100% Core-Data boilerplate code, except for the method:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

I could paste some code, but i wouldn't know what might be interesting...

Any suggestions?

----------EDIT----------

Code for saving new instances:

// create new screenshot and save
ScreenshotInfo *newScreenshot = [NSEntityDescription insertNewObjectForEntityForName:@"ScreenshotInfo" inManagedObjectContext:managedObjectContext];
newScreenshot.date = [[NSDate date] timeIntervalSince1970];
newScreenshot.note = @"click to add note...";
newScreenshot.thumbnailData = [self createThumbnailDataFromImage:image];
PicForScreenshot *newPic = [NSEntityDescription insertNewObjectForEntityForName:@"PicForScreenshot" inManagedObjectContext:managedObjectContext];
newScreenshot.pic = newPic;
newPic.image = screenshotData;
newPic.info = newScreenshot;
NSError *error;
if (![managedObjectContext save:&error]) {
    NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
}

Code for loading:

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"ScreenshotInfo" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSError *error;
pics = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (!pics) {
    [NSException raise:@"Fetch failed" format:@"reAson: %@",[error localizedDescription]];
}

Code for populating tableViewCells:

-(UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
CellView *cell = [tableView dequeueReusableCellWithIdentifier:@"CellView"];
ScreenshotInfo *currentPic = [pics objectAtIndex:indexPath.row];

[[cell image]setImage:[UIImage imageWithData:currentPic.thumbnailData]];
[[cell noteLabel]setText:currentPic.note];
NSDate *date = [NSDate dateWithTimeIntervalSince1970:currentPic.date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"MM/dd/yyyy hh:mma"];
[[cell dateLabel]setText:[dateFormatter stringFromDate:date]];
return cell;

}

This should be the interesting code..

The instances are created and saved in one ViewController, and loaded into another one (the UITableViewController).

@Tommy, you say you're sure that the saving is somehow wrong, but how can the TableView fetch it correctly immediately after creation, if the saving is not right.

Answer 1

1 - Create the object graphic representation inside the project's .xcdatamodeld file. Set the attributes and relationships.

2 - Select the entity and click in Editor menu and select Create NSManagedObject Subclass...

3 - Create new entity instance by setting its context.

var entity: Entity = Entity(context: self.context)

4 - Access/recover an existing NSManaged object graphic entity by the context calling the Persistent Store Coordinator method for the managed object graphic ID using its URL ID.

let objectGraphID = self.context.persistentStoreCoordinator?.managedObjectID(forURIRepresentation: URL(string: "entityObjectGraphicID"))

let nodeEntity = self.context.persistentStoreCoordinator?.managedObjectID(forURIRepresentation: objIDURL!)

Find more about Core Data here: https://cocoacasts.com/exploring-the-core-data-stack

imageFont: https://cocoacasts.com/exploring-the-core-data-stack