How to pass objects between classes using NSNotificationCenter - Fail to pass objects - ios

Question

My code:
NSDictionary *dict = #{#"1": #"_infoView3",
#"2": [NSNumber numberWithFloat:_showSelectionView.frame.size.height]
};
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillShow:)
name:#"UIKeyboardWillShowNotification"
object:dict];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardDidHide:)
name:#"UIKeyboardDidHideNotification"
object:dict];
and :
- (void) keyboardWillShow:(NSNotification *)note {
NSDictionary *userInfo = [note userInfo];
CGSize kbSize = [[userInfo objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
// move the view up by 30 pts
CGRect frame = self.view.frame;
frame.origin.y = -kbSize.height;
[UIView animateWithDuration:0.3 animations:^{
self.view.frame = frame;
}];
}
- (void) keyboardDidHide:(NSNotification *)note {
// move the view back to the origin
CGRect frame = self.view.frame;
frame.origin.y = 0;
[UIView animateWithDuration:0.3 animations:^{
self.view.frame = frame;
}];
}
But those two methods is not working when the keyboard is showing up or hiding.
And those two methods is working if I pass object nil, instead dict.
I don't know where is the problem, please help me , Thank you.

Answer 1

As I can see you are trying to post object at observer side. It is quite opposite, see the example below.
Receiver class
- (void)viewDidLoad {
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(receiveNotification:)
name:#"myNotification"
object:nil];
}
- (void)receiveNotification:(NSNotification *)notification
{
if ([[notification name] isEqualToString:#"myNotification"]) {
NSDictionary *myDictionary = (NSDictionary *)notification.object;
//doSomething here.
}
}
Sender Class
- (void)sendNotification {
[[NSNotificationCenter defaultCenter] postNotificationName:#"myNotification" object:YOUR_DICTIONARY];
}

Answer 2

That's because the object parameter is designed to specify the particular object to observe, not for passing arbitrary data to the called selector.
From the reference:
notificationSender
The object whose notifications the observer wants
to receive; that is, only notifications sent by this sender are
delivered to the observer.
If you pass nil, the notification center doesn’t use a notification’s
sender to decide whether to deliver it to the observer.