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iOS

Posted by Carl Martin
Carl Martin
12,088 Points

How do I implement UIAlertController using Swift?

I'm trying to show UIAlerts instead of just printing errors to the console. I read Apple's documentation, but there isn't much info about how to implement this in Swift.

This is the basic syntax I could piece together from other sources:

let alertController = UIAlertController(title: "Title of Alert", message: "Type message here.", preferredStyle: .Alert)

let OKAction = UIAlertAction(title: "OK", style: .Default) { (action) in
    // ...
}
alertController.addAction(OKAction)

self.presentViewController(alertController, animated: true) {
    // ...
}

Whenever I implement this in the downloadJSONFromURL function in the NetworkOperation.swift file, I get the error Value of type 'NetworkOperation' has no member 'presentViewController'.

What did I do wrong?

1 Answer

Carl Martin
Carl Martin
12,088 Points

I found the answer. The problem was that I was trying to present a view, while not being in the ViewController. The following code worked in the NetworkOperation.swift file from the Build a Weather App with Swift Course:

dispatch_async(dispatch_get_main_queue(), {
                        let HTTPAlert = UIAlertController(title: "GET Request not Successful", message: "HTTP Status Code: \(httpResponse.statusCode)", preferredStyle: .Alert)

                        let OKAction = UIAlertAction(title: "OK", style: .Default) { (action) in
                            print("User clicked OK")
                        }
                        HTTPAlert.addAction(OKAction)

                        UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(HTTPAlert, animated: true, completion: nil)
                    })