CODEWITHSUNDEEP
iosswiftmvvmswift2
ton
ton

Reputation: 1145

MVVM: "ViewModel" for AppDelegate

My Swift project uses MVVM and I'm wondering what's a way of having a "ViewModel" for my AppDelegate, that could be accessed by all the other ViewControllers. I understand that the AppDelegate isn't really a ViewController to have its own ViewModel, if strictly following MVVM model all throughout the app.

I want to have a state for my whole app for when the user is logged out, downloading something, etc. Perhaps someday the "ViewModel" would have plenty more use.

Should I just have global variables for these statuses or is there a way I can have my AppDelegate have a viewModel property, then let my ViewControllers access it? It just seems "less clean" for me having global objects that aren't constants (that's only what I feel).

I'm also using ReactiveCocoa 4, if that would be of any help.

Upvotes: 1

Views: 1441

Answers (2)

cjnevin
cjnevin

Reputation: 311

Dependency injection would be the best approach, you can have a class that manages the App's routing and passes the shared objects down the hierarchy. 

class ApplicationNavigator {
   let loginManager = LoginManager()

   init(window: UIWindow) {
       let exampleViewModel = ExampleViewModel()
       let exampleViewController = ExampleViewController(loginManager: LoginManager, viewModel: exampleViewModel)

       let navigationController = UINavigationController(rootViewController: exampleViewController)
       window.rootViewController = navigationController
       window.makeKeyAndVisible()
   }
}

Then in the AppDelegate didFinishLaunchingWithOptions

var navigator: ApplicationNavigator?

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    window = UIWindow(frame: UIScreen.main.bounds)
    navigator = ApplicationNavigator(window: window!)
    return true
}

Upvotes: 0

Christopher Mann
Christopher Mann

Reputation: 201

While allowing the AppDelegate to be a catch all is a common pitfall to avoid I don't think a ViewModel for the AppDelegate is the best solution. An alternative solution would be to create a "manager" class (or struct) using a singleton that could store login state for the app. That way your login state would be accessible to the rest of the app without adding clutter to the AppDelegate.

Upvotes: 1

Related Questions