CODEWITHSUNDEEP
core-datansmanagedobjectnsmanagedobjectcontext
Shane Hsu
Shane Hsu

Reputation: 8357

Core Data Problems with saving changes in NSManagedObjectContext

I am experiencing problems with how I handle my Core Data NSManagedObjectContext.

I can create NSManagedObject in my NSManagedObjectContext, but I failed to save the value.

Here's what I got:

_lesson.title = _titleField.text;

int priority = [_priorityField.text intValue];
int difficulty = [_difficultyField.text intValue];
int time = [_timeField.text intValue];
int sortIndex = 0;
if ( time == 0 )
{
    sortIndex = 101;
}
else
{
    sortIndex = priority * ( difficulty / time );
}
_lesson.priority = [NSNumber numberWithInt:priority];
_lesson.difficulty = [NSNumber numberWithInt:difficulty];
_lesson.time = [NSNumber numberWithInt:time];
_lesson.sortIndex = [NSNumber numberWithInt:sortIndex];
NSError* error = nil;
[[(AppDelegate*)[[UIApplication sharedApplication] delegate] managedObjectContext] save:&error];

Everything before the saving is working perfectly, I used NSLog to verify if each value is really saved in _lesson.

And _lesson is sent from here:

if ( [[segue identifier] isEqualToString:@"addLesson"] )
{
    LessonViewController* destination = [[LessonViewController alloc]init];
    Lesson* lesson = (Lesson*)[NSEntityDescription insertNewObjectForEntityForName:@"Lesson" inManagedObjectContext:_managedObjectContext];
    destination.lesson = lesson;
}
else if ( [[segue identifier] isEqualToString:@"editLesson"] )
{
    LessonViewController* destination = [[LessonViewController alloc]init];
    NSIndexPath* index = [_tableView indexPathForCell:(UITableViewCell*)sender];
    [_managedObjectContext deleteObject:[_lessonArray objectAtIndex:index.row]];
    Lesson* lesson = (Lesson*)[_lessonArray objectAtIndex:index.row];
    destination.lesson = lesson;
}

After debugging for two hours, I cannot find my error. Please help!

I will include my full code below:

https://www.dropbox.com/sh/eu62ie9svbbqdmm/u1hYUICfjy

That is my full source code. (I copied and pasted and created a mess. So, Dropbox!)

Thanks in advance.

Upvotes: 0

Views: 183

Answers (1)

Martin R
Martin R

Reputation: 539685

This line looks suspicious:

[_managedObjectContext deleteObject:[_lessonArray objectAtIndex:index.row]];

You delete the Lesson object before passing it to the LessonViewController, so that saving the context will delete that object from the store, and not save a (modified) object, as you probably intended.

It seems to me that you should just delete that line in your code.

ADDED: There is an error in your prepareForSegue method: You create a new view controller with

LessonViewController* destination = [[LessonViewController alloc]init];

Instead, you must use the destination view controller of the seque:

LessonViewController *destination = [segue destinationViewController];

Upvotes: 1

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