Stick to Keyboard Animation Curve

pseudocode.m

// We may use it in viewWillAppear/viewWillDisappear

- (void) addKeyboardObserver
{
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
}

- (void) removeKeyboardObserver
{
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
}

// Notifcation Callbacks

- (void)keyboardWillShow:(NSNotification *)notification
{
    [self saveContainerOriginalFrame]; // save current state, application detail
    
    [self showKeyboardCloseBarButton]; // put keyboard close button somehwere
    
    [self keyboardAnimateBlock:^(CGFloat keyboardHeight){
        
        [self setContainerViewFrameWhenKeyboardHasHeight:keyboardHeight]; // application but we use keyboard height
        
    } usingNotification:notification];
}

- (void)keyboardWillHide:(NSNotification *)notification
{
    [self hideKeyboardCloseBarButton]; // remove keyboard close button if any
    
    [self keyboardAnimateBlock:^(CGFloat keyboardHeight){
        
        [self setContainerViewToOriginalFrame]; // application detail
        
    } usingNotification:notification];
}

// Actual animate Keyboard Block

- (void)keyboardAnimateBlock:(void(^)(CGFloat))block usingNotification:(NSNotification *)notification
{
    NSDictionary *userInfo = [notification userInfo];
    
    NSTimeInterval       animationDuration = [[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    UIViewAnimationCurve animationCurve    = [[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue];
    CGRect               keyboardFrame     = [[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    
    CGFloat keyboardHeight = keyboardFrame.size.height;
    
    [UIView animateWithDuration:animationDuration delay:0.0 options:(animationCurve | UIViewAnimationOptionBeginFromCurrentState) animations:^{
        
        block(keyboardHeight);
        
    } completion:nil];
}

// let me know if anything was missed