TextfieldAutoRaiseUp.m

// 1. Before using following code snippet, make sure to add textfields on a UIScrollView
// 2. The following code snippet will lead the first responder textfield just top of showing keyboard.
// 3. The trick is to set enough scrolling space for scroll view to raise all textfields up. 
//    When target textfield is touched, the scroll view will do the animation automatically and raise textfields up.  
// 4. Do not combine other technique to raise up textfields over keyboard. 

- (instancetype)init 
{
   self = [super init];
   if (self) {
    [[NSNotificationCenter defaultCenter] addObserver:self 
   	                                       selector:@selector(keyboardDisappeared:) 
   	                                           name:UIKeyboardWillHideNotification
   	                                         object:nil];
    
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(KeyboardWillChangeFrame:) 
                                                 name:UIKeyboardWillChangeFrameNotification
                                               object:nil];
   }
   return self;
}

- (void)keyboardDisappeared:(NSNotification*)notification
{
    scrollView.contentInset = UIEdgeInsetsZero;
}

- (void)KeyboardWillChangeFrame:(NSNotification*)notification
{
    NSDictionary *keyboardInfo = [notification userInfo];
    NSValue *keyboardFrameBegin = [keyboardInfo valueForKey:UIKeyboardFrameEndUserInfoKey];
    CGRect keyboardFrame = [keyboardFrameBegin CGRectValue];
    
    scrollView.contentInset = UIEdgeInsetsMake(0.0f, 0.0f, keyboardFrame.size.height, 0.0f);
}