核心数据：deleteObject不会触发表更新

Question

我有一个带菜单项的UITableView，当菜单改变时，服务器将新列表推送到设备。当我添加菜单项时，显示列表的表视图会自动更新，或者在提交更改时更改它们。

但是，当我删除一个对象时，这不会反映在列表中（当我更改顺序时，也就是说，这意味着对象的'level'字段）。

这些更改仅在我完全关闭（终止）应用程序并重新启动后显示。

是否有一个简单的原因导致更新未被触发？

for(DOMenuItem* item in _oldMenuIdList){
    [[self managedObjectContext] deleteObject:item]; 
}

NSError *error;

if(![[self managedObjectContext] save:&error]) {
    NSLog(@"Error!");
}

[编辑：

@interface DOMenuItem : NSManagedObject {

}

@property (nonatomic, strong) NSNumber * id;
@property (nonatomic, strong) NSString * action;
@property (nonatomic, strong) NSString * title;
@property (nonatomic, strong) NSString * section;
@property (nonatomic, strong) NSNumber * level;
@property (nonatomic, strong) NSNumber * published;
@property (nonatomic, strong) NSString * icon;
@property (nonatomic, strong) NSDate * lastUpdate;
@property (nonatomic, strong) DOMenuItem * parent;
@property (nonatomic, strong) DOLang * language;
@property (nonatomic, strong) NSSet* children;
@property (nonatomic, strong) NSSet* groups;

@end

@interface DOMenuItem (CoreDataGeneratedAccessors)
- (void)addChildren:(NSSet *)value;
- (void)removeChildren:(NSSet *)value;

- (void)addGroups:(NSSet *)value;
- (void)removeGroups:(NSSet *)value;
- (void)addGroupsObject:(DOGroup *)value;
- (void)removeGroupsObject:(DOGroup *)value;
@end

-

- (NSFetchedResultsController *) createFetchedResultsController:(NSString*) cachName sectionString:(NSString*)sectionString sortBySection:(bool)sortBySection {
    // Set up the fetched results controller (object who requests will own).

    // Create the fetch request for the entity.
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:_objectName inManagedObjectContext:[self managedObjectContext]];
    [fetchRequest setEntity:entity];

    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:_defaultSortField ascending:_sortAscending];
    NSMutableArray *sortDescriptors = [[NSMutableArray alloc] init];
    if(sortBySection && _sectionNameKeyPath != nil){
        // Add section sorting at beginning        
         NSSortDescriptor *sortSectionDescriptor = [[NSSortDescriptor alloc] initWithKey:sectionString ascending:NO];
        [sortDescriptors addObject:sortSectionDescriptor];
    }
    [sortDescriptors addObject:sortDescriptor];

    [fetchRequest setSortDescriptors:sortDescriptors];
    [fetchRequest setFetchLimit:0]; 

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:[self managedObjectContext] sectionNameKeyPath:sectionString cacheName:cachName];

    //[sortDescriptors release];    

    return aFetchedResultsController;
}


- (NSFetchedResultsController*) findChildrenOfMenu:(DOMenuItem*) parentMenu {
    NSPredicate* predicate;

     if(parentMenu == nil){
         predicate = [NSPredicate predicateWithFormat:@"(((ANY groups.validTime > %@) && (ANY groups.active == YES)) || (ANY groups.universal == YES)) && (parent == NULL) && (language.enabled == YES)", [NSDate date]];
         //predicate = [NSPredicate predicateWithFormat:@"(parent == NULL)"];
     } else {
         predicate = [NSPredicate predicateWithFormat:@"(((ANY groups.validTime > %@) && (ANY groups.active == YES)) || (ANY groups.universal == YES)) && (parent == %@) && (language.enabled == YES)", [NSDate date], parentMenu];
     }

    [NSFetchedResultsController deleteCacheWithName:_cacheName];

    NSFetchedResultsController* aFetchedResultsController = [self createFetchedResultsController:_cacheName sectionString:_sectionNameKeyPath sortBySection:YES];    
    [aFetchedResultsController.fetchRequest setPredicate:predicate];
    [aFetchedResultsController.fetchRequest setFetchLimit:0];

    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:_defaultSortField ascending:YES];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

    [aFetchedResultsController.fetchRequest setSortDescriptors:sortDescriptors];        

    // Fetch the records and handle an error
    NSError *fetchError;

    if (![aFetchedResultsController performFetch:&fetchError]) {
        // Handle the error.
        // This is a serious error and should advise the user to restart the application
        NSLog(@"Fetching data error: %@", [fetchError localizedDescription]);
    }

    return aFetchedResultsController;    
}

[编辑2：] 在UIViewController中：

- (void)viewDidLoad
{
iDomsAppDelegate *delegate = (iDomsAppDelegate *)[[UIApplication sharedApplication] delegate];

// Get the menu's
_objects = [[[DOMenuItemsController alloc] init:[delegate managedObjectContext]] findChildrenOfMenu:(DOMenuItem*) _parentMenu];

[_objects setDelegate:self];
}

[编辑3：]

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
    [self.tableView beginUpdates];
}


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

    switch(type) {
        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]
                          withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex]
                          withRowAnimation:UITableViewRowAnimationFade];
            break;
        case NSFetchedResultsChangeMove:
            NSLog(@"NEED TO LOOK AT THIS!");
            break;
        case NSFetchedResultsChangeUpdate:
            NSLog(@"NEED TO LOOK AT THIS!");
            break;

    }
}


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

    UITableView *tableView = [self tableView];

    switch(type) {
        case NSFetchedResultsChangeInsert: {
            //NSLog(@"Inserted!");
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:aNewIndexPath]
                             withRowAnimation:UITableViewRowAnimationFade];
            }
            break;

        case NSFetchedResultsChangeDelete:{
            //NSLog(@"Delete");

            // Skip if previous in section had same commonId
            NSLog(@"Table delete... r:%li - s:%li", (long)aIndexPath.row, (long)aIndexPath.section);

            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:aIndexPath]
                             withRowAnimation:UITableViewRowAnimationFade];
            }
            break;

        case NSFetchedResultsChangeUpdate:
            //NSLog(@"Update menu");
            [(DOPrototypeCell*) [tableView cellForRowAtIndexPath:aIndexPath] populateCell:[_objects objectAtIndexPath:aIndexPath]];
            [tableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:aIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeMove:{
            //NSLog(@"Move");
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:aIndexPath]
                             withRowAnimation:UITableViewRowAnimationFade];

            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:aNewIndexPath]
                             withRowAnimation:UITableViewRowAnimationFade];
            }
            break;
    }
}


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    @try {
        [self.tableView endUpdates];
    } @catch (NSException *exception) {
        NSLog(@"Caught error on finding tabelview update: %@", exception.description);
        [self.tableView reloadData];
    }

    [self checkViewheight];
}