Lock direction of UIPanGestureRecognizer - ios

Question

I have a UIPanGestureRecognizer that I use to pull up a view. the view starts at x = 160, y= 817 and when it is flicked up, I want it to go to 160,284. And When it is flicked back down I want it to automatically go back to the starting point. Here is my code so far:
-(IBAction) dragMe: (UIPanGestureRecognizer *)recognizer {
CGPoint translation = [recognizer translationInView:recognizer.view.superview];
recognizer.view.center = CGPointMake(recognizer.view.center.x, + recognizer.view.center.y + translation.y);
[recognizer setTranslation:CGPointMake(0, 0) inView:recognizer.view.superview];
if (recognizer.state == UIGestureRecognizerStateEnded) {
CGPoint velocity = [recognizer velocityInView:recognizer.view.superview];
CGFloat magnitude = sqrtf((velocity.y * velocity.y));
CGFloat slideMult = magnitude / 100;
NSLog(#"magnitude: %f, slideMult: %f", magnitude, slideMult);
float slideFactor = 0.1 * slideMult; // Increase for more of a slide
CGPoint finalPoint = CGPointMake(recognizer.view.center.x,
recognizer.view.center.y + (velocity.y * slideFactor));
finalPoint.x = MIN(MAX(finalPoint.x, 160), recognizer.view.superview.bounds.size.width);
finalPoint.y = MIN(MAX(finalPoint.y, 284), recognizer.view.superview.bounds.size.height);
[UIView animateWithDuration:slideFactor*1 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
recognizer.view.center = finalPoint;
} completion:nil];
}
}
I don't want the user to be able to move it at all horizontally, just vertically.