Core Data: app crashed when accesing to NSManagedObject attribute

Question

I describe the problem. I have an CoreData entity "New". I'm using a fetchedResultsController with a tableView to present the objects. The problem is when app tries to update a label, it crashed (cell has two labels, but app always crashes in the same sentence, updating the same label...).

Some code here:

• That is the definition of the CoreDataManager:

{

// MARK: - Shared Instance

/**
*  This class variable provides an easy way to get access
*  to a shared instance of the CoreDataStackManager class.
*/
class func sharedInstance() -> CoreDataStackManager {

    struct Singleton {
        static let instance = CoreDataStackManager()
    }
    return Singleton.instance
}

// MARK: - The Core Data stack. The code has been moved, unaltered, from the AppDelegate.
lazy var applicationDocumentsDirectory : NSURL = {

    let urls  = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
    return urls[urls.count-1]
}()

lazy var managedObjectModel: NSManagedObjectModel = {

    let modelURL = NSBundle.mainBundle().URLForResource("Model", withExtension: "momd")!
    return NSManagedObjectModel(contentsOfURL: modelURL)!
}()

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {

    let coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent(SQLITE_FILE_NAME)

    var failureReason = "There was an error creating or loading the application's saved data."
    do {
        try coordinator?.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
    } catch {
        // Report any error we got.
        var dict = [String: AnyObject]()
        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
        dict[NSLocalizedFailureReasonErrorKey] = failureReason

        dict[NSUnderlyingErrorKey] = error as NSError
        let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
        // Replace this 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 \(wrappedError), \(wrappedError.userInfo)")
        abort()
    }

    return coordinator
}()

lazy var managedObjectContext: NSManagedObjectContext = {

    let coordinator = self.persistentStoreCoordinator
    var managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
    managedObjectContext.persistentStoreCoordinator = coordinator

    return managedObjectContext
}()

// MARK: - Core Data Saving support
func saveContext() {

    if managedObjectContext.hasChanges {

        managedObjectContext.performBlockAndWait {
            do {
                try self.managedObjectContext.save()
            } catch {
                let nserror = error as NSError
                NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
                abort()
            }
        }
    }

• Here, where the app crashes:

   func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCellWithIdentifier("HotNewsCell") as! NewsTableViewCell let new = fetchedResultsController.objectAtIndexPath(indexPath) as! New configureCell(cell, new: new) return cell } private func configureCell(cell: NewsTableViewCell, new: New) { cell.titleLabel.text = new.title /* Next line is where app crashes :( */ cell.descriptionLabel.text = new.newBody if let url = NSURL(string: new.photoReference) { cell.activityIndicator.startAnimating() if new.image != nil { cell.imageViewNews.image = new.image cell.activityIndicator.stopAnimating() } else { let task = NetworkRequests.sharedInstance().makeImageRequestFromURL(url) { (data, error) in guard error == nil else { print(error) return } guard let data = data else { print("No data available") return } let image = UIImage(data: data) new.image = image dispatch_async(dispatch_get_main_queue()) { cell.imageViewNews.image = image cell.activityIndicator.stopAnimating() } } cell.taskToCancelifCellIsReused = task } }

It's strange, because if I comment "cell.descriptionLabel.text = new.newBody", app works perfectly.

Thanks!

EDIT

Error was EXC_BAD_ACCESS. Then, I enabled NSZombie, and the error is "message sent to deallocated instance".

Answer 1

I believe this is an artefact of using an attribute name which begins new.... . To avoid the problem, just change the name of the attribute.

See also this answer to an unrelated question, which highlights the problem with new... . From the document identified in that answer (the Clang documentation), it seems technically the problem would not arise if the character immediately after "new" is a lower case letter. So newbody would be OK, whereas newBody is not. Also, for completeness, the following prefixes should likewise be avoided (though they are unlikely choices for attribute names):

• alloc
• copy
• mutableCopy
• init

Interestingly, Xcode (at least version 7.3; not sure about previous versions) will not permit these attribute names in Objective-C, giving a compiler error:

Property follows Cocoa naming convention for returning 'owned' objects

Sadly the Swift compiler does not give any error or warning.