SwiftUI Complex Snippets Cheatsheet

This page restructures the original SwiftUI snippets into a readable Markdown cheatsheet. All original comments and code are preserved exactly; only headings and fenced code blocks were added.

Perform an action on return from background

// Perform an action on return from background

struct ContentView: View {
    @Environment(\.scenePhase) private var scenePhase

    var body: some View {
        Text("Hello, world!")
            .padding()
            .onAppear {
                // Perform tasks that should run when the view appears
                performTask()
            }
            .onChange(of: scenePhase) { newPhase in
                if newPhase == .active {
                    // Perform tasks that should run when the app comes back from background
                    performTask()
                }
            }
    }

    private func performTask() {
        // Your task goes here
        print("Task performed")
    }
}

Sheets

// Sheets

struct ContentView: View {
  @Environment(\.scenePhase) private var scenePhase

  var body: some View {
    VStack {
      Text("Hello, world!")
    }
    .sheet(isPresented: $isShowingEndTimeSheet) {
      SettingsDateSheetView(
        handler: updateEndTime,
        initHours: envModel.endTimeHours,
        initMinutes: envModel.endTimeMinutes,
        hoursToCompare: envModel.startTimeHours,
        minutesToCompare: envModel.startTimeMinutes,
        isCurrentLater: true
      )
      // to turn off interactions with the sheet
      .interactiveDismissDisabled(true)
      // to limit the size
      .presentationDetents([.height(350)])
    }
  }
}

Nested TabView

// Nested TabView

  // inner TabView
  TabView(selection: $viewModel.selectedTab) {
    // pages
  }
  // remove tabBar for inner
  .tabViewStyle(PageTabViewStyle(indexDisplayMode: .never))

Back from background mode

// Back from background mode

struct SomeView: View {
  @Environment(\.scenePhase) private var scenePhase

  var body: some View {
    VStack {
      Text("Text")
    }
    .onChange(of: scenePhase) { newPhase in
      if newPhase == .active {
        Task {
          DispatchQueue.main.async {
              // Do something async
          }
        }
      }
    }
  }
}

Foreground/background via notifications

// Another way of taking app from background or foreground
struct SomeView: View {
  var body: some View {
    VStack {
      Text("Text")
    }
    .onReceive(NotificationCenter.default.publisher(for: UIApplication.willResignActiveNotification)) { _ in
        // app is going to the background, so do something
    }
    .onReceive(NotificationCenter.default.publisher(for: UIApplication.willEnterForegroundNotification)) { _ in
        // app is coming to the foreground, so do something else
    }
  }
}

Lifecycle modifiers quick reference

// works ONLY when returning from background
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willEnterForegroundNotification))
// works every time a view appears on the screen — becomes active
.onChange(of: scenePhase)
// handle async operations only on Mount
.task
// same as task but sync operations
.onAppear

Track swipe gestures

// Track swipe gestures
struct ContentView: View {
    var body: some View {
    VStack {
      Text("Text")
    }
    .gesture(DragGesture(minimumDistance: 3.0, coordinateSpace: .local)
        .onEnded { value in
            print(value.translation)
            switch(value.translation.width, value.translation.height) {
                case (...0, -30...30):  print("left swipe")
                case (0..., -30...30):  print("right swipe")
                case (-100...100, ...0):  print("up swipe")
                case (-100...100, 0...):  print("down swipe")
                default:  print("no clue")
            }
        }
    )
  }
}