>取消分配或取消已注册的对象.
>以观察者身份移除对象.
>未注册为观察员.
>注册错误通知或发布错误通知.

我很高兴地说,我很确定这些都不会发生.我想最有可能的是,对象在某些时候被无效并重新创建,但它在初始化时注册通知.

这是我注册的地方：

/**
 *  initialises an object with a unique file url
 *
 *  @param  url                         the url to set as the file url
 */
- (id)initWithFileURL:(NSURL *)url
{
    if (self = [super initWithFileURL:url])
    {
        self.entries                    = [[NSMutableArray alloc] init];

        //  we want to be notified when a note has changed
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(noteChanged)
                                                     name:@"com.andbeyond.jamesvalaitis.notesChanged"
                                                   object:self];

        NSLog(@"Just registered for 'com.andbeyond.jamesvalaitis.notesChanged'");
    }

    return self;
}

这是我发布通知的地方：

/**
 *  save the note content
 */
- (void)saveNote
{
    if (_isChanged)
    {
        //  save to the text view to the note's contents
        self.note.noteContent           = self.noteView.text;

        //  post a notification that we changed the notes
        [[NSNotificationCenter defaultCenter] postNotificationName:@"com.andbeyond.jamesvalaitis.notesChanged" object:nil];

        NSLog(@"Just posted 'com.andbeyond.jamesvalaitis.notesChanged'");

        //  make sure we know it's already saved
        _isChanged                          = NO;
    }
}

这是未被调用的方法：

/**
 *  called when a note has changed
 */
- (void)noteChanged:(NSNotification *)notification
{
    NSLog(@"Just received for 'com.andbeyond.jamesvalaitis.notesChanged'");

    //  save the notes
    [self saveToURL:self.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:^(BOOL success)
    {
        if (success)
            NSLog(@"Note updated.");
    }];
}

这是控制台澄清我注册并发布通知：

2012-11-15 13:27:50.958 iCloud Custom[11269:907] Just registered for
‘com.andbeyond.jamesvalaitis.notesChanged’

2012-11-15 13:28:24.184 iCloud Custom[11269:907] Just posted
‘com.andbeyond.jamesvalaitis.notesChanged’

The whole project can be found here.