Swift - How to use a closure to fire a function in a view model? - swift

Question

I am watching the video series
Swift Talk #5
Connecting View Controllers
url: https://talk.objc.io/episodes/S01E05-connecting-view-controllers
In this video series they remove all the prepareForSegue and use an App class to handle the connection between different view controllers.
I want to replicate this, but specifically only in my current view model; but what I don't get is how to connect view controllers through a view model (or even if you're meant to)
In their code, at github: https://github.com/objcio/S01E05-connecting-view-controllers/blob/master/Example/AppDelegate.swift
They use do this within their view controller
var didSelect: (Episode) -> () = { _ in }
This runs;
func showEpisode(episode: Episode) {
let detailVC = storyboard.instantiateViewControllerWithIdentifier("Detail") as! DetailViewController
detailVC.episode = episode
navigationController.pushViewController(detailVC, animated: true)
}
In the same way, I want to use my ViewController to use my ViewModel for a menu button press (relying on tag).
My code follows;
struct MainMenuViewModel {
enum MainMenuTag: Int {
case newGameTag = 0
}
func menuButtonPressed(tag: Int) {
guard let tagSelected = MainMenuTag.init(rawValue: tag) else {
return
}
switch tagSelected {
case .newGameTag:
print ("Pressed new game btn")
break
}
}
func menuBtnDidPress(tag: Int) {
print ("You pressed: \(tag)")
// Do a switch here
// Go to the next view controller? Should the view model even know about navigation controllers, pushing, etc?
}
}
class MainMenuViewController: UIViewController {
#IBOutlet var mainMenuBtnOutletCollection: [UIButton]!
var didSelect: (Int) -> () = { _ in }
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func mainMenuBtnPressed(_ sender: UIButton) {
let tag = (sender).tag
self.didSelect(tag)
}
}
What I don't understand is how do I connect the command
self.didSelect(tag)
to the function
func menuButtonPressed(tag: Int)
within my ViewModel
As I understand it, according to the swift talk video is that the idea is that the view controller are "plain" and that the view model handles all the major stuff, like menu button presses and then moving to different view controllers as necessary.
How do I connect the didSelect item to my viewModel function?
Thank you.

Answer 1

You should set didSelect property for your controller like here:
func showEpisode(episode: Episode) {
let detailVC = storyboard.instantiateViewControllerWithIdentifier("Detail") as! DetailViewController
detailVC.episode = episode
detailVC.didSelect = { episode in
// do whatever you need
// for example dismiss detailVC
self.navigationController.popViewController(animated: true)
// or call the model methods
self.model.menuButtonPressed(episode)
}
navigationController.pushViewController(detailVC, animated: true)
}