objective-c - IBAction陷入循环

好的，我有一个与iCal同步的IBAction，它也由CD模型中“ name”属性的KVO触发，因此，当该属性更改时，将触发该Action。发生的情况是，一旦IBAction到达末尾，它将跳到KVO声明，该声明又一次又一次地触发Action，这就是循环发生的地方。

这是一些代码。 IBAction…

- (IBAction)sync:(id)sender {
    [syncButton setTitle:@"Syncing..."];
    NSString *dateText = (@"Last Sync : %d", [NSDate date]);
    [syncDate setStringValue:dateText];
    NSManagedObjectContext *moc = [self managedObjectContext];
    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");
}

到达终点时（以某种方式）触发KVO宣言…

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

然后，它再次触发IBAction。这是循环发生的原因，因为它被卡在此处并不断触发动作。

谁能知道地球上正在发生什么？？？

最佳答案

您正在触发任何符合KVO的属性的选择器sync:。
您应该过滤任何使用sync方法更改的键路径，以避免递归。

我将执行以下操作：


设置断点并检查值
keyPath找出哪些更改
正在开始递归。
筛选出触发递归的关键路径的更改


要么


同步时分离所有观察者：启动并在完成后重新附加它们

关于objective-c - IBAction陷入循环，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/1548291/