waitUntilAllTasksAreFinished error Swift

Question

I have this call in my loginViewController when Submit button is pressed:

let http = HTTPHelper()
    http.post(\"http://someUrl.com/Login/userEmail/\\(username.         


        

Answer 1

Your checkLogin function is being called on another thread, so you need to switch back to the main thread before you can call self.performSegueWithIdentifier. I prefer to use NSOperationQueue:

func checkLogin(succeed: Bool, msg: String) {
    if (succeed) {
        NSOperationQueue.mainQueue().addOperationWithBlock {
            self.performSegueWithIdentifier("logInTrue", sender: self)
        }        
    }
}

Alternate: xCode 10.1 1/2019

func checkLogin(succeed: Bool, msg: String) {
    if (succeed) {
        OperationQueue.main.addOperation {
            self.performSegue(withIdentifier: "logInTrue", sender: self)
           }        
      }
 }

Answer 2

I was also having same issue, got resolved by taking reference from above answer. Thank you @Nate

var storyBoard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
var vc: UINavigationController = storyBoard.instantiateViewControllerWithIdentifier("AppViewController") as! UINavigationController

NSOperationQueue.mainQueue().addOperationWithBlock {
    self.presentViewController(vc, animated: true, completion: nil)
}

Answer 3

With Xcode 8.0 and Swift 3, this has been modified to the following construct:

OperationQueue.main.addOperation{
    <your segue or function call>
}

Answer 4

I was having this issue when trying to change the contents of a text box from inside an Async Task.

The solution was using the DispatchQueue (Xcode 8.0 and Swift 3.0):

    DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
       self.textBox.text = "Some Value"
       }