ToggleDemo.swift

import SwiftUI

class Foo: ObservableObject {
    @Published var toggle = false
}

struct ContentView: View {
    @EnvironmentObject var foo: Foo
    var body: some View {
        VStack {
            Text(foo.toggle ? "On" : "Off")
            Outer()
        }
    }
}

struct Outer: View {
    var body: some View {
        Inner()
    }
}

struct Inner: View {
    @EnvironmentObject var foo: Foo
    var body: some View {
        Toggle(isOn: $foo.toggle) {
            Text("Toggle!")
        }
    }
}