CODEWITHSUNDEEP
ioscompletionhandler
Josh O'Connor
Josh O'Connor

Reputation: 4962

Cancel completion handler (iOS)

I have a textfield, which fetches data from an API everytime the textField text changes, and updates the table.

override func viewDidLoad() {
    super.viewDidLoad()

    searchTextField.addTarget(self, action: #selector(textFieldDidChange), for: UIControlEvents.editingChanged)
}

func textFieldDidChange() {

    let queryString = self.searchTextField.text

    SearchWSFacade.getSearchResults(queryString: queryString) {
         (error) in

         if (error == nil) {
             self.tableView.reloadData()
         } 
    }
}

This works wonderfully, only if the user types slow (allows data to load before typing next character). If the user types fast, we run into issues, because of multiple calls to reloadData.

This could be solved if I cancelled the completion handler when searching when a previous search is occurring. How do I do this? Or is there a better solution?

Upvotes: 1

Views: 268

Answers (2)

Russell
Russell

Reputation: 5554

You could set a simple flag in the UIViewController containing the text field - busyCallingAPI, perhaps - set it true when you start the API call, set it false in the completion handler, and in textFieldDidChange only make the call if busyCallingAPI is false

Upvotes: 0

Abizern
Abizern

Reputation: 150665

If you use Operations, you can set up dependencies so that one doesn't start until the next one completes. And, unlike blocks, Operations can be cancelled.

Upvotes: 1

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