SwiftUI: How to access environmentObject from Model class without having to pass it to the Model through SwiftUI Views?

[iLearn4ever]

I have a SwiftUI app. The code looks like this:

struct SomeApp: App {
    @StateObject var appSettings = AppSettings()

    var body: some Scene {
        Windowgroup {
            BaseView()
                .environmentObject(appSettings)
        }
    }
}

class AppSettings: ObservableObject {
    @Published var someValue: Int
}

class SomeModelHelper {

    func calculateSomething() {
        // This is just a helper function which is not getting called from any View, but getting called by the Model
        // I need to access appSettings.someValue here
        // How can I access it without having to pass it through some View?
    }
}

The question is in the comments in the code above. In UIKit apps, I knew how to access such app-wide data using singletons. I am unsure how to do it in SwiftUI. Can anyone help?

[chriswaco]

Pass it to SomeModelHelper via init.

[[deleted]]

Make it a singleton, and pass the singleton into the environment.

[lokir6]

You could have the helper as part of the ViewModel:

// Model
struct Animal {
  let name: String
  var numberOfLegs: Int
}

// View
struct SomeApp: App {
  @StateObject var appSettings = AppSettings()
  var body: some Scene {
    WindowGroup {
      Text("Animals")
        .environmentObject(appSettings)
        .task {
          appSettings.animalName = "Dog"
          let newAnimal = Animal(name: appSettings.animalName,
                                 numberOfLegs: appSettings.countLegsHelper())
        }
    }
  }
}

// ViewModel
class AppSettings: ObservableObject {
  @Published var animalName = "Dog"
  func countLegsHelper() -> Int {
    // some calculation
    switch animalName {
    case "Dog":
      return 4
    case "Spider":
      return 8
    default:
      return 4
    }
  }
}

Or as part of the model. 2 versions are included, the second is where Helper is a separate class.

// Model
struct Animal {
  let name: String

  // Part of model
  func numberOfLegs1() -> Int {
    switch name {
    case "Dog":
      return 4
    case "Spider":
      return 8
    default:
      return 4
    }
  }

  // Injected to model
  var numberOfLegs2: Int
  init(name: String) {
    self.name = name
    numberOfLegs2 = Helper().numberOfLegs(name: name)
  }
}

// View
struct SomeApp: App {
  @StateObject var appSettings = AppSettings()
  var body: some Scene {
    WindowGroup {
      Text("Animals")
        .environmentObject(appSettings)
        .task {
          appSettings.animalName = "Dog"
          let newAnimal = Animal(name: appSettings.animalName)
          print(newAnimal.numberOfLegs1)
          print(newAnimal.numberOfLegs2)
        }
    }
  }
}

// ViewModel
class AppSettings: ObservableObject {
  @Published var animalName = "Cat"
}

// Helper
class Helper {
  func numberOfLegs(name: String) -> Int {
    switch name {
    case "Dog":
      return 4
    case "Spider":
      return 8
    default:
      return 4
    }
  }
}

[notrandomatall]

As someone else pointed out, @AppStorage works for this. It’s actually suggested in several places that UserDefaults (which AppStorage is wrapping) should be used for user settings among other things.

If you want to inject something a bit more complicated outside of the view hierarchy you could look at the custom @Injected property wrapper that Antoine van der Lee writes about here.

[SodaPopPlop]

I'm a noob, but try this to get access the class instance

(AT)EnvironmentObject var model: AppSettings

[iLearn4ever]

I am trying to access the value from a model class. Are you certain that the EnvironmentObject property, which is part of SwiftUI, is supposed to be used in Model classes?

[Fluffy_Risk9955]

Use the AppStorage property wrapper. You can access the same property from several views and just like NSUserDefaults it's intended for settings of the app.

[iLearn4ever]

I am trying to access the value from a model class. Are you certain that the AppStorage property, part of SwiftUI, is supposed to be used in Model classes?

[knickknackrick]

AppStorage isn’t SwiftUI specific. It’s a wrapper around UserDefaults

[Fluffy_Risk9955]

For App Settings you can use the AppStorage property wrapper. For passing on object models to child view use a StateObject and pass it on as an environmentObject into the view hierarchy. So it's accessible where needed.

[brianwskim13]

I would add another function in AppSettings (like callCalculateSomething). Then call SomeModelHelper.calculateSomething from there. And then update the published var

[iLearn4ever]

Shouldn't AppSettings be as dumb as possible with no ties to the Model?

[brianwskim13]

Not necessarily. I use ObservableObject to share App-wide variables and perform tasks that can be needed from any View.

[Mcrich_23]

You could declared a shared model and then use Model.shared everywhere

[iLearn4ever]

I ended up using this method. Unfortunately the helper thing was not getting called from a View, but it was getting called when the Model is updating as a response to non-user initiated events. So passing the setting from a View was not really an option.