AttributeGraph: cycle detected through attribute using #State in playgrounds - ios

Question

I'm trying to use SwiftUI's #State in playground. Here's my code:
import UIKit
import PlaygroundSupport
import SwiftUI
struct ContentView: View {
#State private var showGreeting = false
var body: some View {
Form {
Button(action: {
self.showGreeting.toggle()
}) {
Text("Toggle Greeting")
}
if showGreeting {
Text("Hello World!")
}
}
}
}
let viewController = UIHostingController(rootView: ContentView())
PlaygroundPage.current.liveView = viewController
I can see the button on the live view. But if I click it, it doesn't show the text. A second click does reveal the text. Further clicks don't seem to make any difference visually.
On each click, I get the following message in log area:
=== AttributeGraph: cycle detected through attribute 38 ===
Need some help understanding what this means in this context and why the state is not behaving naturally.
Note: I'm running macOS Mojave, so I don't have option of SwiftUI previews. I'm making do with live preview of playgrounds.

Answer 1

There's nothing wrong with your SwiftUI, and it runs fine when pasted into a new project.
If you change the Form to a VStack, it works fine in the playground. Using a List gives you the same error. Maybe a bug, I'd report it to Apple.
In my experience, if you're stuck on Mojave for the time being, just set up a project where you can run the simulator. It takes just a couple seconds to compile and run, and you wind up saving time when your SwiftUI playgrounds crash, get weird errors like this, etc.