SwiftUI NavBar button not working while timer updates view - swiftui

Question

Seems there's an issue triggering the NavBar button while timer updates the view.
In the example below, the Close button works, but the NavBar button Cancel, doesn't.
Any idea why? Or how to fix
struct ContentView: View {
#State var isPresented = false
var body: some View {
Button(action: {
isPresented = true
}, label: {
Text("Button")
})
.sheet(isPresented: $isPresented, content: {
ModalView()
})
}
}
class Model: ObservableObject {
private var monitorTimer: Timer?
#Published var someThing: Bool = false
init() {
startMonitoring()
}
func startMonitoring() {
monitorTimer = Timer.scheduledTimer(withTimeInterval: 0.01, repeats: true, block: { _ in
self.someThing.toggle()
})
}
}
struct ModalView: View {
#Environment(\.presentationMode) private var presentationMode
#StateObject var model = Model()
var body: some View {
NavigationView {
VStack{
if model.someThing {
Text("True")
} else {
Text("False")
}
Button(action: {
presentationMode.wrappedValue.dismiss()
}, label: {
Text("Close")
})
}
.navigationBarTitle("Modal")
.navigationBarItems(
leading:
Button("Cancel") {
presentationMode.wrappedValue.dismiss()
})
}
}
}

Answer 1

Here is tested workaround (Xcode 12 / iOS 14). The solution is to separate subviews to avoid global refresh, like below
Note: by the way - don't forget to stop timer on close modal, because state object remains alive, so now your timer runs even after sheet get closed
struct ModalView: View {
#StateObject var model = Model()
var body: some View {
InternalModal().environmentObject(model)
}
}
struct InternalModal: View {
#Environment(\.presentationMode) private var presentationMode
var body: some View {
NavigationView {
VStack{
UpdatingView()
Button(action: {
presentationMode.wrappedValue.dismiss()
}, label: {
Text("Close")
})
}
.navigationBarTitle("Modal")
.navigationBarItems(
leading:
Button(action: {
presentationMode.wrappedValue.dismiss()
}) {
Text("Cancel")
})
}
}
}
struct UpdatingView: View {
#EnvironmentObject var model: Model
var body: some View {
if model.someThing {
Text("True")
} else {
Text("False")
}
}
}