Styjun

scroll.contentOffset = CGPointMake(scroll.frame.size.width*pageNo, 0);

Here is an implementation for Swift 4:

func scrollToPage(page: Int, animated: Bool) 
 var frame: CGRect = self.scrollView.frame
 frame.origin.x = frame.size.width * CGFloat(page)
 frame.origin.y = 0
 self.scrollView.scrollRectToVisible(frame, animated: animated)

and is easily invoked by calling:

self.scrollToPage(1, animated: true)

Edit:

A nicer way of doing this is to support both horizontal and vertical pagination. Here is a convenient extension for that:

extension UIScrollView 

 func scrollTo(horizontalPage: Int? = 0, verticalPage: Int? = 0, animated: Bool? = true) 
 var frame: CGRect = self.frame
 frame.origin.x = frame.size.width * CGFloat(horizontalPage ?? 0)
 frame.origin.y = frame.size.width * CGFloat(verticalPage ?? 0)
 self.scrollRectToVisible(frame, animated: animated ?? true)
 

This creates an extension on UIScrollView where you can scroll to any page, vertical or horisontal.

self.scrollView.scrollTo(horizontalPage: 0)
self.scrollView.scrollTo(verticalPage: 2, animated: true)
self.scrollView.scrollTo(horizontalPage: 1, verticalPage: 2, animated: true)

scrollRectToVisible was not working for me, so I had to animate the contentOffset. This code works in swift 3.

func scrollToPage(_ page: Int) 
 UIView.animate(withDuration: 0.3) 
 self.scrollView.contentOffset.x = self.scrollView.frame.width * CGFloat(page)
 

For Swift 3 this is an extension that I find very convenient:

extension UIScrollView 
 func scrollToPage(index: UInt8, animated: Bool, after delay: TimeInterval) 
 let offset: CGPoint = CGPoint(x: CGFloat(index) * frame.size.width, y: 0)
 DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: 
 self.setContentOffset(offset, animated: animated)
 )
 

And you call it like this:

scrollView.scrollToPage(index: 1, animated: true, after: 0.5)

You can do it this way :

CGRect lastVisibleRect;
CGSize contentSize = [_scrollView contentSize];
lastVisibleRect.size.height = contentSize.height; 
lastVisibleRect.origin.y = 0.0; 
lastVisibleRect.size.width = PAGE_WIDTH; 
lastVisibleRect.origin.x = contentSize.width - PAGE_WIDTH * (_totalItems - pageIndex); // total item of scrollview and your current page index

[_scrollView scrollRectToVisible:lastVisibleRect animated:NO];

Here is a static method in swift:

static func scrollToPage(scrollView: UIScrollView, page: Int, animated: Bool) 
 var frame: CGRect = scrollView.frame
 frame.origin.x = frame.size.width * CGFloat(page);
 frame.origin.y = 0;
 scrollView.scrollRectToVisible(frame, animated: animated)

First create a UIScrollView extension like:

extension UIScrollView 

 func setCurrentPage(position: Int) 
 var frame = self.frame;
 frame.origin.x = frame.size.width * CGFloat(position)
 frame.origin.y = 0
 scrollRectToVisible(frame, animated: true)
 

then just call:

self.scrollView.setCurrentPage(position: 2) // where 2 is your desired page

If scrollRectToVisible doesn't work try this :

let frame = scrollView.frame
 let offset:CGPoint = CGPoint(x: CGFloat(sender.currentPage) * frame.size.width, y: 0)
 self.scrollView.setContentOffset(offset, animated: true)

Swift Solution

func changePage(pageControl: UIPageControl) 

 let page = CGFloat(pageControl.currentPage)
 var frame = self.scrollView.frame
 frame.origin.x = frame.size.width * page
 frame.origin.y = 0
 self.scrollView.scrollRectToVisible(frame, animated: true)

Additional to this code that mjdth added, remember to place it in the viewWillAppear or viewDidAppear.

CGRect frame = scrollView.frame;
frame.origin.x = frame.size.width * pageNumberYouWantToGoTo;
frame.origin.y = 0;
[scrollView scrollRectToVisible:frame animated:YES];