Using callbacks to reproduce UIAlertViewController - ios

Question

I want to reproduce the functionality of the UIAlertController as the class isn't very customisable. So here is what I did:
Create a DeleteDeckViewController that only has two buttons Yes, and No, with a callback method
class DeleteDeckViewController: UIViewController {
var deleteDeck : ((deleteDeck : Bool) -> ())?
#IBAction func yesButton(sender: AnyObject) {
deleteDeck!(deleteDeck: true)
}
#IBAction func noButton(sender: AnyObject) {
deleteDeck!(deleteDeck: false)
}
}
In the main view controller when the delete button is pressed it creates a popup DeleteDeck
func handleDelete(detailDeckView: DetailDeckView) {
let deleteDeckViewController = DeleteDeckViewController(nibName: "DeleteDeckViewController", bundle: nil)
let popup = PopupDialog(viewController: deleteDeckViewController, transitionStyle: .BounceDown, buttonAlignment: .Horizontal, gestureDismissal: true)
presentViewController(popup, animated: true, completion: nil)
deleteDeckViewController.deleteDeck(true) { () -> Void in
print("Deck deleted")
}
}
What I want to do is to use a callback to tell my main view controller whether the user pressed yes or no and then do some actions depending on yes or no. Although, I don't know the correct way to do it. I've read a few articles on callbacks, but I don't know how to apply it in this situation. I've tried using delegates it's just that I would need to pass the DetailDeckView object around without it being used so that's why I thought callback would be a better choice.
Would someone be able to point me in the right direction?

Answer 1

Within DeleteDeckViewController you have declared the deleteDeck variable as a function. Therefore, when you use an instance of this class, you need to set it as a variable. Therefore you code would look more like that below (untested):
func handleDelete(detailDeckView: DetailDeckView) {
let deleteDeckViewController = DeleteDeckViewController(nibName: "DeleteDeckViewController", bundle: nil)
deleteDeckViewController.deleteDeck = myDeleteHandler
let popup = PopupDialog(viewController: deleteDeckViewController, transitionStyle: .BounceDown, buttonAlignment: .Horizontal, gestureDismissal: true)
presentViewController(popup, animated: true, completion: nil)
}
func myDeleteHandler(shouldDelete: Bool) {
if shouldDelete {
print("Delete deck")
}
}
Also, in your code, rather than using deleteDeck! which will fail if deleteDeck is nil, it is better practice to use code like:
if let deleteDeck = self.deleteDeck {
deleteDeck(true)
}
This will create a local non-Optional variable called deleteDeck, that can be assured to not contain nil.
You could build this code into DeleteDeckViewController to streamline further:
class DeleteDeckViewController: ....
func showDialog(vc: UIViewController, completion: ((deleteDeck : Bool) -> Void)?) {
self.deleteDeck = completion
let popup = PopupDialog(viewController: vc, transitionStyle: .BounceDown, buttonAlignment: .Horizontal, gestureDismissal: true)
presentViewController(popup, animated: true, completion: nil)
}