Working with the keyboard

@interface MainViewController ()

// Declare some methods that will be called when the keyboard is about to be shown or hidden
- (void)willShowKeyboard:(NSNotification *)notification;
- (void)willHideKeyboard:(NSNotification *)notification;

@end

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Register the methods for the keyboard hide/show events
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(willShowKeyboard:) name:UIKeyboardWillShowNotification object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(willHideKeyboard:) name:UIKeyboardWillHideNotification object:nil];
    }
    return self;
}

- (void)willShowKeyboard:(NSNotification *)notification {
    NSDictionary *userInfo = [notification userInfo];
    
    // Get the keyboard height and width from the notification
    // Size varies depending on OS, language, orientation
    CGSize kbSize = [[userInfo objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
    NSLog(@"Height: %f Width: %f", kbSize.height, kbSize.width);

    // Get the animation duration and curve from the notification
    NSNumber *durationValue = userInfo[UIKeyboardAnimationDurationUserInfoKey];
    NSTimeInterval animationDuration = durationValue.doubleValue;
    NSNumber *curveValue = userInfo[UIKeyboardAnimationCurveUserInfoKey];
    UIViewAnimationCurve animationCurve = curveValue.intValue;
    
    // Move the view with the same duration and animation curve so that it will match with the keyboard animation
    [UIView animateWithDuration:animationDuration
                          delay:0.0
                        options:(animationCurve << 16)
                     animations:^{
                         self.commentImageView.frame = CGRectMake(0, self.view.frame.size.height - kbSize.height - self.commentImageView.frame.size.height, self.commentImageView.frame.size.width, self.commentImageView.frame.size.height);
                     }
                     completion:nil];
}