iOS Keyboard Avoiding with Auto Layout

keyboard-autolayout.m

// in -loadView or similar…
    self.completeButtonBottomConstraint = [NSLayoutConstraint constraintWithItem:self.completeButton attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:v attribute:NSLayoutAttributeBottom multiplier:1.0 constant:-1.0*IDPCompleteButtonBottomSpacing];

// in -viewWillAppear:…
    [NSNotificationCenter.defaultCenter addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
    [NSNotificationCenter.defaultCenter addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];

- (void)keyboardWillShow:(NSNotification *)note {
    [self updateBottomConstraintFromNotification:note];
}

- (void)keyboardWillHide:(NSNotification *)note {
    [self updateBottomConstraintFromNotification:note];
}

- (void)updateBottomConstraintFromNotification:(NSNotification *)note {
    NSDictionary *userInfo = note.userInfo;

    CGFloat animationDuration = [as_option(userInfo[UIKeyboardAnimationDurationUserInfoKey], NSNumber) floatValue];
    CGRect keyboardEndFrame = [as_option(userInfo[UIKeyboardFrameEndUserInfoKey], NSValue) CGRectValue];
    CGRect convertedKeyboardEndFrame = [self.view convertRect:keyboardEndFrame fromView:self.view.window];
    NSUInteger rawAnimationCurve = [as_option(userInfo[UIKeyboardAnimationCurveUserInfoKey], NSNumber) unsignedIntegerValue] << 16;
    UIViewAnimationOptions animationOptions = (UIViewAnimationOptions)rawAnimationCurve;

    self.completeButtonBottomConstraint.constant = -1.0f * (CGRectGetMaxY(self.view.bounds) - CGRectGetMinY(convertedKeyboardEndFrame) + IDPCompleteButtonBottomSpacing);
    [UIView animateWithDuration:animationDuration delay:0.0 options:(UIViewAnimationOptions)UIViewAnimationOptionBeginFromCurrentState|animationOptions animations:^{
        [self.view layoutIfNeeded];
    } completion:nil];
}

uses https://gist.github.com/cdzombak/93adfdc3f55c7f8299cd for as_option.