[[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardDidHide:) 
                                             name:UIKeyboardDidHideNotification 
                                           object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardWillShow:) 
                                             name:UIKeyboardWillShowNotification 
                                           object:nil];

在某些时候,我想删除这些观察者,而不是打电话

[[NSNotificationCenter defaultCenter] removeObserver:self];

因为这会删除所有观察者,我还有其他观察者,我不想删除它们.我怎么才能删除那两个？