CODEWITHSUNDEEP
iosobjective-ccore-dataruntime-errornsfetchedresultscontroller
Nick
Nick

Reputation: 547

Core Data - Runtime Crash when creating NSFetchedResultsController

I'm using a TableViewController class that is much like the one that is created when you start a new Master-Detail Application project in Xcode. As such, I'm using the same code that is pre-populated in the TableViewController class for my own use. However, I'm getting a runtime crash and I'm not sure why. I use this exact code in another class of my app and it works perfectly.

- (NSFetchedResultsController *)fetchedResultsController
{
    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Binder" inManagedObjectContext:[appDelegate managedObjectContext]];
    [fetchRequest setEntity:entity];

    // Edit the sort key as appropriate.
    //NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timeStamp" ascending:NO];
    //NSArray *sortDescriptors = @[sortDescriptor];

    //[fetchRequest setSortDescriptors:sortDescriptors];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".

//This is where it crashes
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:[appDelegate managedObjectContext] sectionNameKeyPath:nil cacheName:@"Master"];
//End crash
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&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.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _fetchedResultsController;
}

I'm not sure what other code snippets to include here. Output doesn't tell me anything when the crash happens, and Xcode jumps to this part of the Main Thread:

libsystem_kernel.dylib`__kill:
0x972893b0:  movl   $786469, %eax
0x972893b5:  calll  0x9728b4c2                ; _sysenter_trap
0x972893ba:  jae    0x972893ca                ; __kill + 26 //This is highlighted
0x972893bc:  calll  0x972893c1                ; __kill + 17
0x972893c1:  popl   %edx
0x972893c2:  movl   27739(%edx), %edx
0x972893c8:  jmpl   *%edx
0x972893ca:  ret    
0x972893cb:  nop

Any thoughts? Thanks

Upvotes: 2

Views: 1357

Answers (3)

Nick
Nick

Reputation: 547

Thanks to @flashfabrixx, the problem was that I was not using a sort descriptor and they are required when using a NSFetchedResultsController. Once I added the sort descriptor back in, everything worked perfectly.

Upvotes: 6

Hal Mueller
Hal Mueller

Reputation: 7646

Passing a nil managed object context to initWithFetchRequest:managedObjectContext:sectionNameKeyPath:cacheName: will throw an exception. I'm surprised you're not seeing anything in the console log though.

Try NSAssert() to verify that your MOC, and the Binder entity, are both non-nil.

If the cache name in your NSFetchedResultsController has been used for another FRC, you'll see an error unless the two controllers' fetch requests are identical. Set a nil (or different) cacheName: and see if you get a different result.

Upvotes: 0

Mundi
Mundi

Reputation: 80265

Well, the only non-standard thing you are doing is that you are using a managed object context from the app delegate. This is really not recommended, for many good reasons.

Try changing this by adding a context property to your master controller and using that context to create your fetched results controller (both for getting a reference to the entity and for the FRC creation).

Finally, ensure your model indeed contains a valid Binder entity.

Upvotes: 0

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