iOS 14.5 trouble updating label text during networking loop - swift

Question

I have a loop that updates a remote database over the network. To keep track of the updates I want to use a counter to update the text of a label after each update. The problem is that the label text only updates after the loop completes. I have tried many combinations of DispatchQueue and DispatchGroup with no success.
The code below illustrates this problem. Thank you for your help.
import UIKit
class ViewController: UIViewController {
var counter = 0
#IBOutlet weak var countLBL: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func startClick(_ sender: Any) {
workloop()
}
func workloop() {
for _ in (0...3) {
networkTask()
counter += 1
countLBL.text = String(counter)
}
}
func networkTask() {
sleep(1)
}
}

Answer 1

Your basic assumptions and approach are wrong.
In all cases, if you execute a function, the UI changes you apply in that function will not be displayed to the screen until you exit the function and the app passes through the event loop.
Further, you should not be making synchronous network calls.
The idea that you'd have code
networkTask()
counter += 1
//update UI with info about completed network task
Is wrong. A function that performs a network task should be written to operate asynchrnously. (It will return immediately, go off and do the network task, and call a completion handler when the task is done. The code might look like this:
networkTask(completion: { results in
DispatchQueue.main.async {
// Code to display the results of the network operation to the UI
}
}
)
The idea of using async functions and completion handlers in Swift is widely covered by Apple, by lots and lots of development blogs, and by countless posts here on SO.