Cannot removeObserver? - ios

Question

I've began to learn iOS development for a few weeks,but this bug confused me a lot....
I just post 4 different observers in a ViewController:(They have different notificationames)
[[NSNotificationCenter defaultCenter]postNotificationName:#"notificationame" object:self userInfo:userinfo];
Then I want to add & remove 4 different observers in another ViewController,like this:
-(void)viewwillappear{
self.localChangeObserver=[[NSNotificationCenter defaultCenter]addObserverForName:#"notificationame" object:nil queue:nil usingBlock:^(NSNotification *note) { }];
}
-(void)viewwilldisappear{
[[NSNotificationCenter defaultCenter]removeObserver:self.localChangeObserver];
}
But this"removeObserver" turns out to be not working.Each time I show this ViewController ,it add one more observer,(and then I hide this VC,nothing removed).So I got a lot of observers at last.
And, putting them in ViewDidLoad/dealloc also do not work.
But,another 2 Observers just work fine.like this:
-(void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
}
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
I really don't know what's wrong with my code.Thanks a lot.

Answer 1

Use following code :
-(void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[[NSNotificationCenter defaultCenter] addObserverForName:#"OBSERVER NAME" object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification *aNotification)
{
//Write your Notification handler Code
}];
}
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"OBSERVER NAME" object:nil];
}
This code is working fine...!!!

Answer 2

Try following code
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"notificationame" object:nil];