UILabel not updating with new value

Could you show more code, where we see all the parts that you describe ?

Hi, thanks for your reply. Here is some part of the code:

This is an event that is being fired at some point.

ConnectionManager.shared.onConnectionShouldStop = { [weak self] in
            
            LogManager.sharedInstance.writeDebugInfo(forString: "Connection should stop. 5 seconds no valid response")
            
            guard let self = self else {
                return
            }
            
            BLEDiscoveryManager.shared.disconnectPeripheral()
            self.disconnectApp(adapterStopped: false)
            DispatchQueue.main.async {
                self.showDevicesMenu()
            }
            
  }

The update to the UILabel is part of the disconnectApp method. Part of disconnect:

func disconnectApp(adapterStopped: Bool) {
        
  //some more code that has nothing to do with the label and works properly
  //…
       
        DispatchQueue.main.async {
            self.peripheralsTableView.reloadData()
            self.updateEverywhereForConnectionLost()
        }
        
 }

Then at some point in updateEverywhereForConnectionLost:

DispatchQueue.main.async {
  for child in self.children {
            if child is SpeedViewController {
                let controller = child as! SpeedViewController
                LogManager.sharedInstance.writeDebugInfo(forString: “Assigning value“)
                controller.speedValueLabel.attributedText = NSAttributedString(string: "-")
            }
        }
}

To test this I have to go to a testing setup, so the debugging is done by logging to a file. The messages logged by LogManager are visible in the log, so the calls are made. But the UILabel does not update. Once or twice I saw it update with some delay of around 5 seconds, but after that it stopped updating at all.

The issue is now fixed. It turned out that there was previous update on the same UILabel that was made on a background thread. It also did not update the label. Then even though the new update was done on the main thread it was not working. Maybe because the value was the same as the one that was set on a background thread.

You create a new instance of the controller, that may be the reason.

Seems also that the quotes in “Assigning value“ or NSAttributedString(string: "-")

are not the correct double quotes.

Try this

DispatchQueue.main.async {
    for child in self.children where child is SpeedViewController {
            LogManager.sharedInstance.writeDebugInfo(forString: "Assigning value")
            child.speedValueLabel.attributedText = NSAttributedString(string: "-")
    }
}

OK, in fact you did upfate the label, but that was superseded by another update.

Note also that those UI updates may be stored for later execution in the main thread, all at once.

Don't forget to mark the thread as closed.