I’m trying to require thing being supplied instead of providing it as a default with defaultValue = Thing(). If I make the environment optional with Thing?, then I have to unwrap it in each View. Without such an approach my initializer always appears to be called twice when I need to pass in a specific instance.

I’m trying with the code below, but it throws the fatal “Thing not provided” as soon as it runs. I’m providing the environment in thingApp, though, so I’m confused why this is happening. It happens even when @Environment(.thing) var thing isn’t used.

import SwiftUI

@main
struct thingApp: App {
    var thing = Thing()

    var body: some Scene {
        WindowGroup {
            ContentView().environment(.thing, thing)
        }
    }
}

struct ContentView: View {
    @Environment(.thing) var thing

    var body: some View {
        Text("count: (self.thing.count)")
    }
}

@MainActor
@Observable class Thing {
    var count: Int = 3

    func inc() {
        self.count = self.count + 1
    }
}

private struct ThingKey: EnvironmentKey {
    static var defaultValue: Thing {
        fatalError("Thing not provided")
    }
}

extension EnvironmentValues {
    var thing: Thing {
        get { self[ThingKey.self] }
        set { self[ThingKey.self] = newValue }
    }
}