Why state drives reactive UI updates in iOS Swift - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a state variable in SwiftUI.

iOS Swift

@State private var count: [1] = 0

Drag options to blanks, or click blank then click option'

AInt

BString

CBool

DDouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using String instead of Int for a number variable.

The @State property wrapper requires a type declaration. Here, count is an integer, so Int is correct.

2fill in blank

medium

Complete the code to update the state variable when the button is pressed.

iOS Swift

Button(action: {
  count [1] 1
}) {
  Text("Increment")
}

Drag options to blanks, or click blank then click option'

A+=

B-=

C*=

D/=

Attempts:

3 left

💡 Hint

Common Mistakes

Using -= which subtracts instead of adds.

To increase the count by 1, use the += operator.

3fill in blank

hard

Fix the error in the code to display the count value in the Text view.

iOS Swift

Text("Count: \( [1] )")

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Aself.count()

B"count"

Ccount()

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Adding parentheses like a function call.

Use the variable name count directly inside string interpolation without parentheses.

4fill in blank

hard

Fill both blanks to create a reactive view that updates when the state changes.

iOS Swift

struct ContentView: View {
  @State private var count: [1] = 0

  var body: some View {
    VStack {
      Text("Count: \(count)")
      Button(action: {
        count [2] 1
      }) {
        Text("Add")
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

AInt

B+=

C-=

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using String type for count.

Using -= which decreases the count.

The state variable count is an integer (Int), and to update it reactively, use += to add 1.

5fill in blank

hard

Fill all three blanks to create a SwiftUI view that shows a toggle and text reflecting its state.

iOS Swift

struct ToggleView: View {
  @State private var isOn: [1] = false

  var body: some View {
    VStack {
      Toggle(isOn: $[2]) {
        Text("Switch")
      }
      Text(isOn ? [3] : "Off")
    }
  }
}

Drag options to blanks, or click blank then click option'

ABool

BisOn

C"On"

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using Int instead of Bool.

Using wrong variable name for binding.

Not using quotes for the "On" string.

The toggle state is a boolean (Bool). The binding uses $isOn. The text shows "On" when true.