Question

In my Class X I post a Notification like this:

[[NSNotificationCenter defaultCenter] addObserver:viewController 
                                             selector:@selector(doThis:) 
                                                 name:@"myNotification" 
                                               object:nil];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"myNotification" object:nil];

In my Class Y I recieve it like this:

- (void) doThis: (NSNotification *) notification {
NSLog(@"It works.");
[uiTextView resignFirstResponder]; }

The console shows the NSLog message but my UITextView does not hide its keyboard.
(In e.g. viewDidLoad the resignFirstResponder/becomeFirstResponder works.)

Is there any special thing I need to do?

Answer 1

As Conrad says, observers should be added and removed by themselves…

Use the best practice to define the name of the notifications as static constants like follows:

static NSString *const kMyNotification = @"myNotification";

Why? because there is a risk that both @”myNotification” might be two different objects and then the notificationName is different and you won’t receive the notification. Since I always declare them as static constants I have never had issues with NSNotifications.

Then use it like this:

To register the observer

[[NSNotificationCenter defaultCenter] addObserver: self 
                                         selector: @selector(doThis:) 
                                             name: kMyNotification 
                                           object: nil];

To post the notification

[[NSNotificationCenter defaultCenter] postNotificationName: kMyNotification 
                                                    object: nil];

To remove the observer:

[[NSNotificationCenter defaultCenter] removeObserver: self];