Alerts (popups)

Simple alert
 DispatchQueue.main.async {
            let alert = UIAlertController(title: "Hello", message: "This is an alert", preferredStyle: UIAlertControllerStyle.alert)
            let cancelAction = UIAlertAction(title: "OK", style: .cancel, handler: nil)
         
            alert.addAction(cancelAction)
            self.present(alert, animated: true)
         
         
        }

Two buttons
   DispatchQueue.main.async {
            let alertController = UIAlertController(title: "Simple", message: "Simple alertView demo with Cancel and Ok.", preferredStyle: UIAlertControllerStyle.alert)
         
            let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel) { (result : UIAlertAction) -> Void in
             
             
             
            }
         
            let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.default) { (result : UIAlertAction) -> Void in
             
             
             
            }
         
            alertController.addAction(cancelAction)
         
            alertController.addAction(okAction)
         
            self.present(alertController, animated: true, completion: nil)
         

        }

Showing it inside a tableviewcell, instead of self.present, use:
UIApplication.shared.keyWindow?.rootViewController?.present(alertController, animated: true, completion: nil)

With input field

let alertController = UIAlertController(title: "Grocery Item", message: "What to buy now?", preferredStyle: UIAlertControllerStyle.alert)
        alertController.addTextField { (textField: UITextField) in
         
        }
     
        let addActionTwo = UIAlertAction(title: "ADD", style: UIAlertActionStyle.default) { (action: UIAlertAction) in
   let itemString : String?
  if(alertController.textFields?.first?.text != "")
{
  itemString = alertController.textFields?.first?.text
}
else{return}
            //what to after they key in data
            self.groceries.append(itemString)
            self.tableView.reloadData()
         
        }
     
        let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.default, handler: nil)
     
        alertController.addAction(addActionTwo)
        alertController.addAction(cancelAction)
present(alertController, animated: true, completion: nil)

If you want to make the input field one with a keypad
look for the method of addTextField with parameter configurationHandler
alert.addTextField(configurationHandler: { textField in
    textField.keyboardType = .numberPad
})