Stepper in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Stepper with a label showing its value.

iOS Swift

struct ContentView: View {
  @State private var value = 0
  var body: some View {
    Stepper("Value: \(value)", value: $value, in: 0...10) [1]
  }
}

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

A.onChange(of: value) { newValue in print(newValue) }

B.background(Color.gray)

C.padding()

D.disabled(true)

Attempts:

3 left

💡 Hint

Common Mistakes

Using .disabled(true) disables the Stepper, which is not intended here.

Using .background(Color.gray) changes background but does not add space.

The .padding() modifier adds space around the Stepper for better appearance.

2fill in blank

medium

Complete the code to limit the Stepper's value between 1 and 5.

iOS Swift

Stepper("Count: \(count)", value: $count, in: [1]) 
  .padding()

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

A5...10

B1...5

C-5...5

D0...10

Attempts:

3 left

💡 Hint

Common Mistakes

Using a range that includes 0 when minimum should be 1.

Using an open range like 1..<5 which excludes 5.

The range 1...5 limits the Stepper's value between 1 and 5 inclusive.

3fill in blank

hard

Fix the error in the Stepper binding to update the value correctly.

iOS Swift

@State private var stepValue = 0

var body: some View {
  Stepper("Step: \(stepValue)", value: [1], in: 0...10)
    .padding()
}

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

AstepValue$

BstepValue

C&stepValue

D$stepValue

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the state variable directly without $ causes a compile error.

Using &stepValue is invalid syntax in SwiftUI.

Use $stepValue to pass a binding to the Stepper so it can update the state.

4fill in blank

hard

Fill both blanks to create a Stepper that increments by 2 and shows the value.

iOS Swift

Stepper("Value: \(value)", value: $value, in: 0...20, step: [1]) [2]

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

A2

B.padding()

C.background(Color.blue)

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using step 1 instead of 2 changes the increment amount.

Forgetting to add padding makes the UI cramped.

The step: 2 makes the Stepper increase by 2 each tap, and .padding() adds space around it.

5fill in blank

hard

Fill all three blanks to create a Stepper with a label, binding, and range.

iOS Swift

struct StepperView: View {
  @State private var count = 0
  var body: some View {
    Stepper([1], value: [2], in: [3])
      .padding()
  }
}

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

A"Count: \(count)"

B$count

C0...10

D"Value: count"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a plain string without interpolation for the label.

Passing count instead of $count for the binding.

Using an incorrect range like 1...5.

The label shows the current count, the binding uses $count, and the range limits values from 0 to 10.

Practice

1. What is the main purpose of a Stepper in iOS Swift UI?

easy

A. To let users increase or decrease a numeric value by tapping plus or minus buttons.

B. To display a list of items in a scrollable view.

C. To navigate between different screens in the app.

D. To input text from the keyboard.

Solution

1. Step 1: Understand Stepper functionality

   A Stepper is a UI control that allows users to increment or decrement a value by tapping plus or minus buttons.

2. Step 2: Compare options with Stepper purpose

   Only To let users increase or decrease a numeric value by tapping plus or minus buttons. describes this behavior correctly; others describe unrelated UI elements.

3. Final Answer:

   To let users increase or decrease a numeric value by tapping plus or minus buttons. -> Option A

4. Quick Check:

   Stepper purpose = increase/decrease number [OK]

Hint: Stepper controls numbers with plus/minus taps [OK]

Common Mistakes:

• Confusing Stepper with text input controls
• Thinking Stepper navigates screens
• Assuming Stepper shows lists

2. Which of the following is the correct way to create a Stepper in SwiftUI with a binding to a variable count?

easy

A. Stepper(count: $count, range: 0...10) { Text("Count: \(count)") }

B. Stepper(value: $count, in: 0...10) { Text("Count: \(count)") }

C. Stepper(value: count, range: 0...10) { Text("Count: \(count)") }

D. Stepper($count, 0...10) { Text("Count: \(count)") }

Solution

1. Step 1: Recall Stepper initializer syntax

   The correct initializer uses value: Binding and in: ClosedRange parameters.

2. Step 2: Check each option

   Stepper(value: $count, in: 0...10) { Text("Count: \(count)") } matches the correct syntax with Stepper(value: $count, in: 0...10). Others have wrong parameter names or missing bindings.

3. Final Answer:

   Stepper(value: $count, in: 0...10) { Text("Count: \(count)") } -> Option B

4. Quick Check:

   Correct Stepper syntax = Stepper(value: $count, in: 0...10) { Text("Count: \(count)") } [OK]

Hint: Use value: $variable and in: range for Stepper [OK]

Common Mistakes:

• Forgetting $ for binding
• Using wrong parameter names like count or range
• Passing value without binding

3. What will be displayed when the user taps the plus button twice on this Stepper code?

@State private var count = 3
Stepper(value: $count, in: 1...5) { Text("Count: \(count)") }

medium

A. Count: 7

B. Count: 6

C. Count: 3

D. Count: 5

Solution

1. Step 1: Understand initial value and range

   The count starts at 3 and can only go from 1 to 5.

2. Step 2: Calculate value after two increments

   After two taps on plus, count increases by 2: 3 + 2 = 5, which is the max allowed.

3. Final Answer:

   Count: 5 -> Option D

4. Quick Check:

   Max limit caps count at 5 [OK]

Hint: Stepper value never exceeds max range [OK]

Common Mistakes:

• Ignoring max limit and expecting 6 or 7
• Not updating count on taps
• Confusing initial value with displayed value

4. Identify the error in this Stepper code snippet:

@State private var count = 0
Stepper(value: count, in: 0...10) { Text("Count: \(count)") }

medium

A. Missing $ before count in value binding

B. Range 0...10 is invalid for Stepper

C. Text label should not use \(count)

D. Stepper cannot use @State variables

Solution

1. Step 1: Check Stepper value parameter

   The value parameter requires a binding, so it must be $count, not just count.

2. Step 2: Verify other parts

   The range 0...10 is valid, Text label syntax is correct, and Stepper can use @State variables.

3. Final Answer:

   Missing $ before count in value binding -> Option A

4. Quick Check:

   Binding needs $ prefix [OK]

Hint: Always use $ for binding variables in Stepper [OK]

Common Mistakes:

• Passing variable without $ causes error
• Thinking range 0...10 is invalid
• Misunderstanding @State usage

5. You want a Stepper that starts at 10, goes up to 50, and increases by 5 each tap. Which code correctly sets this behavior?

hard

A. Stepper(value: $count, in: 10...50, step: 10) { Text("Count: \(count)") }

B. Stepper(value: $count, range: 10...50, step: 5) { Text("Count: \(count)") }

C. Stepper(value: $count, in: 10...50, step: 5) { Text("Count: \(count)") }

D. Stepper(value: $count, in: 10...50) { Text("Count: \(count)") }

Solution

1. Step 1: Identify correct Stepper parameters

   To set step size, use the step: parameter. The range uses in:.

2. Step 2: Check each option

   Stepper(value: $count, in: 10...50, step: 5) { Text("Count: \(count)") } correctly uses value: $count, in: 10...50, and step: 5. Stepper(value: $count, range: 10...50, step: 5) { Text("Count: \(count)") } uses wrong parameter range. Stepper(value: $count, in: 10...50) { Text("Count: \(count)") } misses step size. Stepper(value: $count, in: 10...50, step: 10) { Text("Count: \(count)") } uses wrong step size 10.

3. Final Answer:

   Stepper(value: $count, in: 10...50, step: 5) { Text("Count: \(count)") } -> Option C

4. Quick Check:

   Use in: range and step: size [OK]

Hint: Use step: to set increment size in Stepper [OK]

Common Mistakes:

• Using wrong parameter name 'range' instead of 'in'
• Forgetting to set step size
• Setting wrong step size