CODEWITHSUNDEEP
iphoneobjective-cxcodensnotificationcenternsnotification
derFalke
derFalke

Reputation: 247

NSNotification only NSLog works

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?

Upvotes: 0

Views: 646

Answers (2)

Daniel Sanchez
Daniel Sanchez

Reputation: 461

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];

Upvotes: 2

Conrad Shultz
Conrad Shultz

Reputation: 8808

FWIW, in most, but not all, cases, observers should be added and removed by the observer itself, not by a separate object. (What happens if the observer goes away before the separate object, and fails to have the observer properly removed? Or vice-versa? It makes it all too easy to either leak observers or crash on notifications to deallocated objects.)

Anyhow, first thing's first: have you verified that uiTextView is not nil and points at the first responder? I rather suspect that uiTextView is not what you think it is.

Upvotes: 3

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