ios - UITableView中的deleteObject错误，无法重复

Question

我在 App Store 中有我的第一个应用程序，但收到一个无法在我的任何设备上重现的错误。一位用户报告说，他无法在应用程序崩溃的情况下删除产品。我已经尝试了所有我能想到的重现方法，但没有成功。 iTunes Connect 中没有出现崩溃报告，因此我注册了 Crittercism。现在我知道有三个用户遇到了这个问题。

问题是，即使有崩溃日志，我仍然无法弄清楚应用程序崩溃的原因。当我删除一个项目时，即使是一个没有用户输入信息的新创建的项目，它也不会崩溃。任何有关可以帮助我缩小问题范围的建议将不胜感激。该应用使用核心数据，并且该产品实体与其他实体的所有删除规则都设置为无效或级联。

崩溃日志表明崩溃的原因是“NSInvalidArgumentException - deleteObject:需要非零参数”。这是回溯:

Reported    Name    Reason  App Version     Symbolicated
15-May-12 07:22:06 PM   NSInvalidArgumentException  
-deleteObject: requires a non-nil argument

0   CoreFoundation 0x317a888f __exceptionPreprocess + 162
1   libobjc.A.dylib 0x315f3259 objc_exception_throw + 32
2   CoreData 0x3325cf23 -[NSManagedObjectContext deleteObject:] + 386
3   OnShelf 0x000972e7 0x76000 + 135911
4   CoreFoundation 0x317023fd -[NSObject performSelector:withObject:withObject:] + 52
5   UIKit 0x319f0e07 -[UIApplication sendAction:to:from:forEvent:] + 62
6   UIKit 0x31ab65e7 -[UIBarButtonItem(UIInternal) _sendAction:withEvent:] + 118
7   CoreFoundation 0x317023fd -[NSObject performSelector:withObject:withObject:] + 52
8   UIKit 0x319f0e07 -[UIApplication sendAction:to:from:forEvent:] + 62
9   UIKit 0x319f0dc3 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 30
10  UIKit 0x319f0da1 -[UIControl sendAction:to:forEvent:] + 44
11  UIKit 0x319f0b11 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 492
12  UIKit 0x319f1449 -[UIControl touchesEnded:withEvent:] + 476
13  UIKit 0x319ef92b -[UIWindow _sendTouchesForEvent:] + 318
14  UIKit 0x319ef319 -[UIWindow sendEvent:] + 380
15  UIKit 0x319d5695 -[UIApplication sendEvent:] + 356
16  UIKit 0x319d4f3b _UIApplicationHandleEvent + 5826
17  GraphicsServices 0x32bd822b PurpleEventCallback + 882
18  CoreFoundation 0x3177c523 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 38
19  CoreFoundation 0x3177c4c5 __CFRunLoopDoSource1 + 140
20  CoreFoundation 0x3177b313 __CFRunLoopRun + 1370
21  CoreFoundation 0x316fe4a5 CFRunLoopRunSpecific + 300
22  CoreFoundation 0x316fe36d CFRunLoopRunInMode + 104
23  GraphicsServices 0x32bd7439 GSEventRunModal + 136
24  UIKit 0x31a03cd5 UIApplicationMain + 1080
25  OnShelf 0x00077207 0x76000 + 4615
26  OnShelf 0x000771bc 0x76000 + 4540

在 UITableView 中删除产品的代码唯一不寻常的地方是它首先检查库存数量是否为零。如果不是，则会显示警报，询问用户是否确实要删除该产品。联系我的一位用户确实告诉我，无论库存数量是否为零，他都发生了崩溃，因此崩溃似乎与显示的警报无关。这是代码:

- (void)tableView:(UITableView *)tableView 
            commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
             forRowAtIndexPath:(NSIndexPath *)indexPath
{
Product *product = [fetchedResultsController objectAtIndexPath:indexPath];

// Alert the user if the item is currently in stock
if ([product.details.quantity intValue] > 0) {
    [self showAlert];

    if (editingStyle == UITableViewCellEditingStyleDelete) {
        lastIndexPath = indexPath;
        toDelete = YES;
        NSLog(@"Yes delete");
    } else {
        toDelete = NO;
    }
} else {
    // Delete the managed object.
    NSManagedObjectContext *myContext = [fetchedResultsController managedObjectContext];
    [myContext deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]];

    NSError *error;
    if (![myContext save:&error]) {
        // Update to handle the error appropriately.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        exit(-1);  // Fail
        }        
    }
}


#pragma mark - AlertView Delegate Methods

- (void)showAlert {
    // open a alert with an OK and cancel button
    UIAlertView *alert =[[UIAlertView alloc] initWithTitle: @"Product In Stock"
                                                   message: @"All product data will be deleted" 
                                                  delegate: nil 
                                         cancelButtonTitle: @"Cancel" 
                                         otherButtonTitles:@"OK", nil];
    [alert setDelegate: self];
    [alert show];
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
    if (buttonIndex == 0) {
        //do nothing
    }
    else
    {
        if( toDelete == YES)
        {
            // Delete the managed object.
            NSManagedObjectContext *myContext = [fetchedResultsController managedObjectContext];
            [myContext deleteObject:[fetchedResultsController objectAtIndexPath: lastIndexPath]];

            NSError *error;
            if (![myContext save:&error]) {
                // Update to handle the error appropriately.
                NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
                exit(-1);  // Fail
            }        
        }
    }
}

我正在使用 Apple 教程中的样板 NSFetchedResultsController 委托(delegate)方法:

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
// The fetch controller is about to start sending change notifications, so prepare the table view for updates.
[self.tableView beginUpdates];
}


- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject 
                                                            atIndexPath:(NSIndexPath *)indexPath 
                                                            forChangeType:(NSFetchedResultsChangeType)type 
                                                        newIndexPath:(NSIndexPath *)newIndexPath     {

    UITableView *aTableView = self.tableView;

    switch(type) {

        case NSFetchedResultsChangeInsert:
            [aTableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [aTableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:(DatabaseCell *)[aTableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [aTableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            [aTableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
                                                            atIndex:(NSUInteger)sectionIndex 
                                                            forChangeType:(NSFetchedResultsChangeType)type {

    switch(type) {

        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

    case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
// The fetch controller has sent all current change notifications, so tell the table view to process all updates.
    [self.tableView endUpdates];
}

Answer 1

..回答有点晚了，但最近出现了此错误消息“NSInvalidArgumentException - deleteObject:需要非零参数”。当我快速删除主从 TableView 中的项目并双击删除按钮时，就会发生这种情况。我的问题的解决方法是在调用deleteObject之前检查indexPath是否为零:

    if (indexPath == nil) return;
    [context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];