Sheet and fullScreenCover in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

Difference in dismissal behavior between Sheet and fullScreenCover

In SwiftUI, what is the main difference in how a Sheet and a fullScreenCover are dismissed by default?

A Both Sheet and fullScreenCover can be dismissed by swiping down by default.

B Sheet can be dismissed by swiping down, but fullScreenCover requires explicit dismissal.

C fullScreenCover can be dismissed by swiping down, but Sheet requires explicit dismissal.

D Neither Sheet nor fullScreenCover can be dismissed by swiping down.

💡 Hint

Think about the default user interaction for modal views in iOS.

Sheets in SwiftUI support swipe-to-dismiss by default, allowing users to drag down to close. fullScreenCover modals cover the entire screen and do not support swipe-to-dismiss by default; they require programmatic dismissal.

❓ navigation

intermediate

State variable usage for presenting Sheet vs fullScreenCover

Which SwiftUI state variable type is best suited to control the presentation of a Sheet or fullScreenCover when you want to present a modal based on a Boolean condition?

A @State Bool variable toggled true/false to show or hide the modal.

B @State Array variable holding multiple modal views.

C @State Int variable counting how many times modal was shown.

D @State String variable holding the modal content title.

💡 Hint

Think about what type controls visibility: true means visible, false means hidden.

Using a Boolean @State variable is the standard way to control modal presentation in SwiftUI. Setting it to true shows the modal, false hides it.

❓ lifecycle

advanced

Effect of dismissing a fullScreenCover on parent view lifecycle

When a fullScreenCover is dismissed in SwiftUI, what happens to the parent view's lifecycle?

A The parent view pauses and resumes animations but resets state.

B The parent view reloads completely and resets all its state variables.

C The parent view is destroyed and recreated from scratch.

D The parent view remains active and does not reload or reset its state.

💡 Hint

Consider how modal presentation affects the underlying view in SwiftUI.

Dismissing a fullScreenCover returns control to the parent view without recreating or resetting it. The parent view remains active with its current state intact.

📝 Syntax

advanced

Correct syntax for presenting a Sheet with data binding

Which SwiftUI code snippet correctly presents a Sheet that passes a binding to a detail view?

iOS Swift

struct ContentView: View {
  @State private var showSheet = false
  @State private var selectedName = ""

  var body: some View {
    Button("Show Sheet") {
      showSheet = true
    }
    .sheet(isPresented: $showSheet) {
      DetailView(name: $selectedName)
    }
  }
}

struct DetailView: View {
  @Binding var name: String
  var body: some View {
    TextField("Enter name", text: $name)
  }
}

A .sheet(isPresented: showSheet) { DetailView(name: $selectedName) }

B .sheet(showSheet) { DetailView(name: selectedName) }

C .sheet(isPresented: $showSheet) { DetailView(name: $selectedName) }

D .sheet(isPresented: $showSheet) { DetailView(name: selectedName) }

💡 Hint

Remember to pass bindings with a $ prefix and use the correct parameter name.

The sheet modifier requires a binding to a Boolean for isPresented. The detail view expects a binding, so pass $selectedName. Option C correctly uses $showSheet and $selectedName.

🔧 Debug

expert

Why does fullScreenCover not dismiss when swiping down?

Given this SwiftUI code, why does the fullScreenCover not dismiss when the user swipes down?

struct ContentView: View {
  @State private var showModal = true

  var body: some View {
    Button("Show") { showModal = true }
      .fullScreenCover(isPresented: $showModal) {
        ModalView()
      }
  }
}

struct ModalView: View {
  var body: some View {
    Text("Modal")
  }
}

A fullScreenCover does not support swipe-to-dismiss by default; dismissal must be handled programmatically.

B The @State variable showModal is not toggled to false inside ModalView, so it never dismisses.

C The Button is inside the fullScreenCover, blocking swipe gestures.

D The ModalView must have a NavigationView to enable swipe-to-dismiss.

💡 Hint

Think about default user interactions for fullScreenCover modals.

fullScreenCover modals cover the entire screen and do not support swipe-to-dismiss by default. You must dismiss them by changing the binding variable to false programmatically.