How to use pull to refresh in Swift?

Question

I am building an RSS reader using swift and need to implement pull to reload functionality.

Here is how i am trying to do it.

class FirstViewController: UIViewController,
    UITableViewDelegate, UITableViewDataSource {

   @IBOutlet var refresh: UIScreenEdgePanGestureRecognizer
   @IBOutlet var newsCollect: UITableView

   var activityIndicator:UIActivityIndicatorView? = nil

   override func viewDidLoad() {
       super.viewDidLoad()
       self.newsCollect.scrollEnabled = true
      // Do any additional setup after loading the view, typically from a nib.

      if nCollect.news.count <= 2{
          self.collectNews()
       }
      else{
          self.removeActivityIndicator()
       }
      view.addGestureRecognizer(refresh)
   }



@IBAction func reload(sender: UIScreenEdgePanGestureRecognizer) {
    nCollect.news = News[]()
    return newsCollect.reloadData()
}

I am getting :

Property 'self.refresh' not initialized at super.init call

Please help me to understand the behaviour of Gesture recognisers. A working sample code will be a great help.

Thanks.

Answer 1

Swift 4

var refreshControl: UIRefreshControl!

override func viewDidLoad() {
    super.viewDidLoad()

    refreshControl = UIRefreshControl()
    refreshControl.attributedTitle = NSAttributedString(string: "Pull to refresh")
    refreshControl.addTarget(self, action: #selector(refresh), for: .valueChanged)
    tableView.addSubview(refreshControl) 
}

@objc func refresh(_ sender: Any) {
    //  your code to refresh tableView
}

And you could stop refreshing with:

refreshControl.endRefreshing()

Answer 2

What the error is telling you, is that refresh isn't initialized. Note that you chose to make refresh not optional, which in Swift means that it has to have a value before you call super.init (or it's implicitly called, which seems to be your case). Either make refresh optional (probably what you want) or initialize it in some way.

I would suggest reading the Swift introductory documentation again, which covers this in great length.

One last thing, not part of the answer, as pointed out by @Anil, there is a built in pull to refresh control in iOS called UIRefresControl, which might be something worth looking into.

Answer 3

I built a RSS feed app in which I have a Pull To refresh feature that originally had some of the problems listed above.

But to add to the users answers above, I was looking everywhere for my use case and could not find it. I was downloading data from the web (RSSFeed) and I wanted to pull down on my tableView of stories to refresh.

What is mentioned above cover the right areas but with some of the problems people are having, here is what I did and it works a treat:

I took @Blankarsch 's approach and went to my main.storyboard and select the table view to use refresh, then what wasn't mentioned is creating IBOutlet and IBAction to use the refresh efficiently

//Created from main.storyboard cntrl+drag refresh from left scene to assistant editor
@IBOutlet weak var refreshButton: UIRefreshControl

override func viewDidLoad() {
  ...... 
  ......
  //Include your code
  ......
  ......
  //Is the function called below, make sure to put this in your viewDidLoad 
  //method or not data will be visible when running the app
  getFeedData()
}

//Function the gets my data/parse my data from the web (if you havnt already put this in a similar function)
//remembering it returns nothing, hence return type is "-> Void"
func getFeedData() -> Void{
  .....
  .....
}

//From main.storyboard cntrl+drag to assistant editor and this time create an action instead of outlet and 
//make sure arguments are set to none and note sender
@IBAction func refresh() {
  //getting our data by calling the function which gets our data/parse our data
  getFeedData()

  //note: refreshControl doesnt need to be declared it is already initailized. Got to love xcode
  refreshControl?.endRefreshing()
}

Hope this helps anyone in same situation as me

Answer 4

func pullToRefresh(){

    let refresh = UIRefreshControl()
    refresh.addTarget(self, action: #selector(handleTopRefresh(_:)), for: .valueChanged )
    refresh.tintColor = UIColor.appBlack
    self.tblAddressBook.addSubview(refresh)

}
@objc func handleTopRefresh(_ sender:UIRefreshControl){
    self.callAddressBookListApi(isLoaderRequired: false)
    sender.endRefreshing()
}

Answer 5

This is how I made it work using Xcode 7.2 which I think is a major bug. I'm using it inside my UITableViewController inside my viewWillAppear

refreshControl = UIRefreshControl()
refreshControl!.addTarget(self, action: "configureMessages", forControlEvents: .ValueChanged)
refreshControl!.beginRefreshing()

configureMessages()

func configureMessages() {
    // configuring messages logic here

    self.refreshControl!.endRefreshing()
}

As you can see, I literally have to call the configureMessage() method after setting up my UIRefreshControl then after that, subsequent refreshes will work fine.

Answer 6

Pull to refresh is built in iOS. You could do this in swift like

var refreshControl = UIRefreshControl()

override func viewDidLoad() {
   super.viewDidLoad()

   refreshControl.attributedTitle = NSAttributedString(string: "Pull to refresh")
   refreshControl.addTarget(self, action: #selector(refresh(_:)), for: UIControl.Event.valueChanged)
   tableView.addSubview(refreshControl) // not required when using UITableViewController
}

@objc func refresh(sender:AnyObject) {
   // Code to refresh table view  
}

At some point you could end refreshing.

refreshControl.endRefreshing()