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Xcode – How to initialize a view with a stateobject as a parameter?

struct ProfileEditView: View {
    @ObservedObject var viewModel: UsersViewModel
    @StateObject var auth: Authenticator

    @State var showingImageEditor: Bool = false

    init(_ viewModel: UsersViewModel, _ auth: Authenticator) {
    
        self.viewModel = viewModel
        self.auth = auth
    
        UITableView.appearance().backgroundColor = UIColor.clear
        UITableViewCell.appearance().selectionStyle = .none
    }

    var body: some View { }
}

I am trying to manually intialize a view that takes a StateObject as a parameter. I am getting an error: Cannot assign to property: 'auth' is a get-only property. What is the proper way to write the initializer?

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2

Answers


  1. 0

    I can’t fully reproduce your code without your definitions of Authenticator and UsersViewModel, but I got it to compile:

    class UsersViewModel: ObservableObject {}
class Authenticator: ObservableObject {}

struct ProfileEditView: View {
    @ObservedObject var viewModel: UsersViewModel
    @StateObject var auth: Authenticator

    @State var showingImageEditor: Bool = false

    init(_ viewModel: ObservedObject<UsersViewModel>, _ auth: Authenticator) {

        _viewModel = viewModel
        _auth = StateObject(wrappedValue: auth)

        UITableView.appearance().backgroundColor = UIColor.clear
        UITableViewCell.appearance().selectionStyle = .none
    }

    var body: some View {
        Text("something")
    }
}

    These are the key changes:

    init(_ viewModel: ObservedObject<UsersViewModel>, _ auth: Authenticator) {
    _viewModel = viewModel
    _auth = StateObject(wrappedValue: auth)

    If you don’t understand my changes you should google

    "swift property wrappers"

    to get a better understanding of what property wrappers are and how to use them.

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  2. 0

    In addition to the ‘accepted answer’ there’s a really good example that will allow everyone to reproduce the error and understand how to avoid it.

    Considering there’s a viewModel in a View with a property wrapper @StateObject, there’s no need to initiate a StateObject(wrappedValue: ...) in the constructor as long as there are no private properties in the View. Let’s see an example:

    class MyViewModel: ObservableObject {}

class MyView: View {
   @StateObject var viewModel: MyViewModel
}

    The above example will work by simply using:

    MyView(viewModel: MyViewModel())

    But if we will add a private property to the View:

    class MyView: View {
   @StateObject var viewModel: MyViewModel
   // `test` will produce the protection level error
   private var test = false
}

    Our previous example MyView(viewModel: MyViewModel()) will now produce the following error:

    initializer is inaccessible due to ‘private’ protection level

    So please consider why you declare a property in a View private, perhaps it can be moved to the ViewModel and the issue will be solved in order to utilize the dependency injection principle.

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