How to get iOS keyboard height programmatically

keyboardHeight.m

- (void)viewDidLoad {
	[super viewDidLoad];
    
    [[NSNotificationCenter defaultCenter] addObserver:self 
    					     selector:@selector(keyboardWillShow:) 
    					         name:UIKeyboardWillChangeFrameNotification 
    					       object:nil];
}
 
- (void)keyboardWillShow:(NSNotification *)notification {
    NSLog(@"%f", [notification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue].size.height);
}