Using UIRefreshControl

Pull to refresh has been a standard UI convention in iOS since early days of Twitter. It's easy to include the default pull to refresh control into any scroll view, including UIScrollView, UITableView, or UICollectionView.

Step 1: Create the UIRefreshControl

It's useful to create the UIRefreshControl as an instance variable at the top of the class because you need to access it to stop the loading behavior.

class MyViewController: UIViewController {
    var refreshControl: UIRefreshControl!
    
    ...

Step 2: Add the UIRefreshControl to the Scroll View

In viewDidLoad, add the refresh control as a subview of the scrollview. It's best to insert it at the lowest index so that it appears behind all the views in the scrollview.

override func viewDidLoad() {
    super.viewDidLoad()
    
    refreshControl = UIRefreshControl()
    refreshControl.addTarget(self, action: "onRefresh", forControlEvents: UIControlEvents.ValueChanged)
    scrollView.insertSubview(refreshControl, atIndex: 0)
}

Step 3: Implement the onRefresh Method

In Step 2 above, we said whenever the refreshControl changes state, it should call the onRefresh method. We need to define that method. For prototyping, you can simulate network loading by canceling refreshing after a couple of seconds.

func delay(delay:Double, closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue(), closure)
}

func onRefresh() {
    delay(2, closure: {
        self.refreshControl.endRefreshing()
    })
}