Navigating using enum cases without associated values

[vrutberg]

Hello,

I recently upgraded to version 1.4.0 of this library, and I am receiving warnings about deprecations of some overloaded navigation methods, e.g.:

Warning

'sheet(unwrapping:case:onDismiss:content:)' is deprecated: Chain a '@CasePathable' enum binding into a case directly instead of specifying a case path.

.sheet(
    unwrapping: $viewModel.route,
    case: /SomeViewModel.Route.contactSupport
) { _ in
    FeedbackView(source: .someView)
}

Previously to v1.4.0, I wasn't using CasePathable, but rather just plain enums. Now, as I'm setting out to fix these warnings, I'm updating my Route enums to use @CasePathable. Some of my enum cases don't have any associated values, so a Route enum might look like this:

@CasePathable
enum Route {
    case alert(AlertState<AlertAction>)
    case register
    case serviceError(ServiceError)
    case contactSupport
    case dismiss
}

Updating navigation view modifiers to use the new overloads leads to a problem if the enum case doesn't have any associated value:

Caution

Type 'Void' cannot conform to 'Identifiable'

.sheet(
    item: $viewModel.route.contactSupport
) { _ in
    FeedbackView(source: .someView)
}

That can be fixed by adding an argument id: \.self. However, that will generate another, similar error:

Caution

Type 'Void' cannot conform to 'Hashable'

.sheet(
    item: $viewModel.route.contactSupport, id: \.self
) { _ in
    FeedbackView(source: .someView)
}

And, yeah, that's where I am now. Am I doing something wrong here, or am I missing something obvious? I tried adding custom overloads of .sheet for handling Void, but I couldn't seem to.

I tried looking through all the sample code and case studies, but I couldn't find any place where navigation is done using an enum case without an associated value. Should I not be doing it this way, perhaps? 🤔

Any pointers or feedback is greatly appreciated.

Viktor

PS. I'm a subscriber of Point-Free and have been for years, love the work you guys do! ❤️

[vrutberg]

Alright, so, after talking a walk and clearing my head for a bit, I came up with the following solution/workaround:

.sheet(
    isPresented: Binding(
        get: { viewModel.route.is(\.contactSupport) },
        set: { _ in viewModel.route = nil }
    )
) {
    FeedbackView(source: .someView)
}

I suppose this could be made prettier by adding an extension method on View, but I'm not familiar enough with @CasePathable at this point to know exactly how that should look. I'll look into a bit, and if I come up with anything, I'll update this response.

Edit: I think an extension looking like this might be the way to go:

extension View {
    func sheet(
        item: Binding<Void?>,
        content: @escaping () -> some View
    ) -> some View {
        sheet(
            isPresented: Binding(
                get: { item.wrappedValue != nil },
                set: { _ in item.wrappedValue = nil }
            ),
            content: content
        )
    }
}

It can be used like this:

.sheet(item: $viewModel.route.contactSupport) {
    FeedbackView(source: .someView)
}

[mbrandonw]

Hi @vrutberg, there is a simpler solution to your problem. You can use the isPresented variant of sheet, along with the Binding initializer that turns a Binding<T?> into a Binding<Bool>:

sheet(
  isPresented: Binding($viewModel.route.contactSupport)
) { _ in
  …
}

Can you try that out?

[vrutberg]

Hi @mbrandonw! Oh, I didn't know about that initializer on Binding. That seems like exactly what I want to do (and what I am doing in my own little sheet function 😅, only just a bit more verbose).

I don't know why, but it seems like the compiler is confused about what initializer we are referring to. 🤔

Caution

Cannot convert value of type 'Binding<Void??>' to expected argument type 'Binding<Bool>'

I think it may be due to the compiler not being aware of that initializer, somehow. If I copy and paste the initializer into my project, it works just fine.

I can see the initializer is a part of SwiftUINavigationCore, but it doesn't seem to matter if I import that module explicitly or not (Xcode tells me it's implicitly imported by importing SwiftUINavigation). Hm...

[stephencelis]

@vrutberg Seems strange that you're getting a double-nested optional there (Void??). Can you share a small compiling code sample that has the problem so we have something we can work with?

[vrutberg]

@stephencelis I think I just realized what the problem is. That Binding initializer isn't part of v1.4.0, but it's available on main. That's why it worked when I copied it into my project. 😅

Changing my SPM dependency to point to the main branch resolves the compiler error.

[stephencelis]

@vrutberg I'm not sure why you're seeing that. Here's the initializer in 1.4.0:

https://github.com/pointfreeco/swiftui-navigation/blob/1.4.0/Sources/SwiftUINavigation/Binding.swift#L34-L51

It's in the same state as main.