Calling presentViewController from custom class

Question

I read this post and this one on how to call a presentViewController form outside a UIViewController subclass. In my case, the custom class is a subclass of NSObject. The following approach is the only one that works (from the examples I read):

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

My question: is there a better solution that does not rely on the appDelegate (as I understood this approach is design-wise not very neat)...

Answer 1

I sometimes create a utilities class to display alerts and such. What I usually do is have my methods for presenting view controllers take the current view controller as a parameter. That approach works pretty well.

EDIT:

Here is an example method from a file Utils.swift in one of my projects. It defines a class function that displays a UIAlertController alert on the current view controller:

class Utils
{
  static let sharedUtils = Utils()
  
  class func showAlertOnVC(
    targetVC: UIViewController, 
    var title: String, 
    var message: String)
  {
    title = NSLocalizedString(title, comment: "")
    message = NSLocalizedString(message, comment: "")
    let alert = UIAlertController(
      title: title, 
      message: message, 
      preferredStyle: UIAlertControllerStyle.Alert)
    let okButton = UIAlertAction(
      title:"OK",
      style: UIAlertActionStyle.Default,
      handler:
      {
        (alert: UIAlertAction!)  in
    })
    alert.addAction(okButton)
    targetVC.presentViewController(alert, animated: true, completion: nil)
  }
}

The code above defines a class Utils. Note that it does not have any base class, which is Ok in Swift.

Next it defines a public static variable sharedUtils that you can use to get access to the singleton Utils class.

Finally, it defines a class method showAlertOnVC that can be used to display a UIAlertController alert on top of the current view controller. To use showAlertOnVC you call it from the current view controller and pass self as the targetVC parameter.

Answer 2

This in my opinion is the easiest solution:

class Utils {
  static  func displayTheAlert(targetVC: UIViewController, title: String, message: String){
        let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.Alert)
        alert.addAction((UIAlertAction(title: "OK", style: .Default, handler: {(action) -> Void in
        })))
        targetVC.presentViewController(alert, animated: true, completion: nil)
    }
}

// then to call it

Utils.displayTheAlert(self, title: "Fout", message: "Uw bestelling is nog niet klaar")