Keep getting sigabrt error with core data - iphone

Question

I'm learning about core data at the moment and working on a simple version of apple's core data tutorial (Locations).
Below is the code for the addEvent method:
Event *event = (Event *)[NSEntityDescription insertNewObjectForEntityForName:#"Event" inManagedObjectContext:managedObjectContext];
[event setCreationDate:[NSDate date]];
NSError *error;
if (![managedObjectContext save:&error]) {
// Handle the error.
}
[eventsArray insertObject:event atIndex:0];
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
When this method is triggered I am getting a sigabrt error. However I've found that if i include apple's viewDidLoad code the error doesn't occur anymore and I can't for the life of me figure out why?
Here's the code that stops the error occurring:
- (void)viewDidLoad {
[super viewDidLoad];
// Set the title.
self.title = #"Locations";
// Configure the add and edit buttons.
self.navigationItem.leftBarButtonItem = self.editButtonItem;
addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:#selector(addEvent)];
self.navigationItem.rightBarButtonItem = addButton;
/*
Fetch existing events.
Create a fetch request; find the Event entity and assign it to the request; add a sort descriptor; then execute the fetch.
*/
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Event" inManagedObjectContext:managedObjectContext];
[request setEntity:entity];
// Order the events by creation date, most recent first.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"creationDate" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
[sortDescriptor release];
[sortDescriptors release];
// Execute the fetch -- create a mutable copy of the result.
NSError *error = nil;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if (mutableFetchResults == nil) {
// Handle the error.
}
// Set self's events array to the mutable array, then clean up.
[self setEventsArray:mutableFetchResults];
[mutableFetchResults release];
[request release];
What am i missing? I don't see how a a lack of a fetch request on viewDidLoad causes the error
Thanks

Answer 1

How does your tableview know which events to show?
One side effect of Apple's viewDidLoad method is that it will create the eventsArray. If you don't ever create that but you tell your tableView that you have inserted a row, you'd better have that row available!
You're calling
[eventsArray insertObject:event atIndex:0];
but I bet that without Apple's viewDidLoad method, eventsArray is nil - you will need to create it if it's nil (i.e. eventsArray = [[NSMutableArray alloc] init];

Answer 2

I've had this very same problem while working through Apple's tutorial.
Stepping through with the debugger it is falling over on the
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
line on the
-(void)addEvent
in the RootViewController.m
The reason that the code on the original posters stops the error from occuring is because the line the fires off the location manager is missing from the -(void)viewDidLoad.
[[self locationManager] startUpdatingLocation]
Thus when the
-(void)addEvent
is triggered the procedure is hitting the return and exiting
if (!location) {
return;
}
and is therefore not getting to the offending line, I added the startUpdatingLocation back to the viewDidLoad of the original posters code and the sigabrt error is back again.
I know this isn't an answer but I hope this saves someone else half an hour.