`MapContent` ignores `@Observable` updates – not aligned with SwiftUI expectations

[pjanik]

Environment

• Xcode version: 16.4
• iOS version: 18.6
• Devices affected: any
• Maps SDK Version: 11.14.0

Observed behavior and steps to reproduce

MapContent does not react to @Observable state updates. Here's the minimal test case:

@Observable
class TestViewModel {
  var pluckBearing = false
}

struct MapTestContent: MapContent {
  let viewModel: TestViewModel

  var body: some MapContent {
    if viewModel.pluckBearing {
      Puck2D(bearing: .heading)
    } else {
      Puck2D(bearing: .none)
    }
  }
}

struct MapTest: View {
  let viewModel = TestViewModel()

  var body: some View {
    VStack {
      Map {
        MapTestContent(viewModel: viewModel)
      }

      Button("Toggle Puck Bearing") {
        viewModel.pluckBearing.toggle()
      }
    }
  }
}

Tapping the button has currently no effect.

Expected behavior

Tapping the button should update pluck style. So, I'd expect MapContent get re-evaluated when @Observable state is updated.

Notes / preliminary analysis

The ability to update only the leaf nodes of the map declaration tree could lead to significant performance improvements.

[pjanik]

Hi,

Do you have any updates on whether this is considered relevant and planned to be addressed? It might be more of a missing feature than a bug.

You could compare this behavior with native SwiftUI "content-alike" protocols, such as ToolbarContent, ChartContent, etc.