停止循环

Question

正如我之前的问题中所解释的...

此代码...

- (void)syncKVO:(id)sender {
    NSManagedObjectContext *moc = [self managedObjectContext];
    [syncButton setTitle:@"Syncing..."];
    NSString *dateText = (@"Last Sync : %d", [NSDate date]);
    [syncDate setStringValue:dateText];
    NSEntityDescription *entityDescription = [NSEntityDescription
                                                                                  entityForName:@"projects" inManagedObjectContext:moc];
    NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
    [request setEntity:entityDescription];

    NSError *error = nil;
    NSArray *array = [moc executeFetchRequest:request error:&error];
    if (array == nil)
    {
        NSAlert *anAlert = [NSAlert alertWithError:error];
        [anAlert runModal];
    }
    NSArray *namesArray = [array valueForKey:@"name"];
    NSPredicate *predicate = [CalCalendarStore taskPredicateWithCalendars:[[CalCalendarStore defaultCalendarStore] calendars]];
    NSArray *tasksNo = [[CalCalendarStore defaultCalendarStore] tasksWithPredicate:predicate];
    NSArray *tasks = [tasksNo valueForKey:@"title"];
    NSMutableArray *namesNewArray = [NSMutableArray arrayWithArray:namesArray];
    [namesNewArray removeObjectsInArray:tasks];
    NSLog(@"%d", [namesNewArray count]);        
    NSInteger *popIndex = [calenderPopup indexOfSelectedItem];

    //Load the array
    CalCalendarStore *store = [CalCalendarStore defaultCalendarStore];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);
    NSString *supportDirectory = [paths objectAtIndex:0];
    NSString *fileName = [supportDirectory stringByAppendingPathComponent:@"oldtasks.plist"];

    NSMutableArray *oldTasks = [[NSMutableArray alloc] initWithContentsOfFile:fileName];
    [oldTasks removeObjectsInArray:namesArray];
    NSLog(@"%d",[oldTasks count]);
    //Use the content
    NSPredicate* taskPredicate = [CalCalendarStore taskPredicateWithCalendars:[[CalCalendarStore defaultCalendarStore] calendars]];
    NSArray* allTasks = [[CalCalendarStore defaultCalendarStore] tasksWithPredicate:taskPredicate];

    // Get the calendar
    CalCalendar *calendar = [[store calendars] objectAtIndex:popIndex];
    // Note: you can change which calendar you're adding to by changing the index or by
    // using CalCalendarStore's -calendarWithUID: method        

    // Loop, adding tasks
    for(NSString *title in namesNewArray) {
        // Create task
        CalTask *task = [CalTask task];
        task.title = title;
        task.calendar = calendar;

        // Save task
        if(![[CalCalendarStore defaultCalendarStore] saveTask:task error:&error]) {
                NSLog(@"Error");
                // Diagnostic error handling
                NSAlert *anAlert = [NSAlert alertWithError:error];
                [anAlert runModal];
        }
    } 

    NSMutableArray *tasksNewArray = [NSMutableArray arrayWithArray:tasks];
    [tasksNewArray removeObjectsInArray:namesArray];
    NSLog(@"%d", [tasksNewArray count]);        
    for(NSString *title in tasksNewArray) {
        NSManagedObjectContext *moc = [self managedObjectContext];
        JGManagedObject *theParent = 
        [NSEntityDescription insertNewObjectForEntityForName:@"projects"
                                      inManagedObjectContext:moc];
        [theParent setValue:nil forKey:@"parent"];
        // This is where you add the title from the string array
        [theParent setValue:title forKey:@"name"]; 
        [theParent setValue:[NSNumber numberWithInt:0] forKey:@"position"];

    }

    for(CalTask* task in allTasks)
        if([oldTasks containsObject:task.title]) {
                [store removeTask:task error:nil];
        }

    // Create a predicate for an array of names.
    NSPredicate *mocPredicate = [NSPredicate predicateWithFormat:@"name IN %@", oldTasks];
    [request setPredicate:mocPredicate];

    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];
    [request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];

    // Execute the fetch request put the results into array
    NSArray *resultArray = [moc executeFetchRequest:request error:&error];
    if (resultArray == nil)
    {
        // Diagnostic error handling
        NSAlert *anAlert = [NSAlert alertWithError:error];
        [anAlert runModal];
    }

    // Enumerate through the array deleting each object.
    // WARNING, this will delete everything in the array, so you may want to put more checks in before doing this.
    for (JGManagedObject *objectToDelete in resultArray ) {
        // Delete the object.
        [moc deleteObject:objectToDelete];
    }
    //Save the array
    [namesArray writeToFile:fileName atomically:YES];
    [syncButton setTitle:@"Sync Now"];
    NSLog(@"Sync Completed");
}

触发此代码...

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if ([keyPath isEqualToString:@"name"]) {
        [self performSelector:@selector(syncKVO:)];
    }
}

因为我正在添加对象，并且当核心数据“名称”属性更改时会触发 KVO 方法。

如果 observeValueForKeyPath:ofObject:change:context: 方法是由 syncKVO 方法触发的，我需要停止该方法。我该怎么做？

Answer 1

您可以做的最简单的事情是使用一个实例变量，该变量跟踪您是否正在同步并在设置时忽略观察者的更改。最好在 syncKVO: 的开头和结尾处停止并开始观察，但这取决于您实际观察的内容：如果您观看大量收藏。

Answer 2

看看您的代码，我想知道您是否真的想在保存实体时进行同步，而不是在对象键更改后立即进行同步。我认为您最好完全放弃观察并使用 CoreData 文档 来确定需要更新哪些实体。