Slider in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

Slider Value Change Behavior

What will be the value of the label text after moving the slider to 0.75 in this SwiftUI code?

iOS Swift

struct ContentView: View {
  @State private var sliderValue: Double = 0.5
  var body: some View {
    VStack {
      Slider(value: $sliderValue, in: 0...1)
      Text(String(format: "%.2f", sliderValue))
    }
  }
}

A "0.75"

B "1.00"

C "0.7"

D "75"

💡 Hint

Look at how the slider value is formatted in the Text view.

The slider value is a Double between 0 and 1. The Text uses String(format: "%.2f", sliderValue) which formats the number with two decimal places. So 0.75 becomes "0.75".

❓ lifecycle

intermediate

Slider State Update Timing

In UIKit, when using UISlider with addTarget for .valueChanged, when is the action method called?

A Only when the slider is tapped, not dragged

B Only when the user finishes dragging and releases the slider

C Only when the slider value is set programmatically

D Every time the slider value changes during dragging

💡 Hint

Think about how UISlider reports changes as the user moves the thumb.

The .valueChanged event fires continuously as the slider thumb moves, so the action method is called every time the value changes during dragging.

📝 Syntax

advanced

Correct SwiftUI Slider Binding Syntax

Which option correctly binds a slider value to a @State variable in SwiftUI?

iOS Swift

struct ContentView: View {
  @State private var volume: Double = 0.3
  var body: some View {
    Slider(value: /* fill here */, in: 0...1)
  }
}

A $volume

B Binding(volume)

C &volume

D volume

💡 Hint

Remember how to pass a binding to a SwiftUI control.

In SwiftUI, to bind a control to a @State variable, you pass the binding using the $ prefix. So $volume is correct.

🔧 Debug

advanced

Why Slider Value Does Not Update Label

Given this SwiftUI code, why does the label not update when the slider moves? struct ContentView: View { var sliderValue: Double = 0.5 var body: some View { VStack { Slider(value: $sliderValue, in: 0...1) Text(String(format: "%.2f", sliderValue)) } } }

A Text formatting is wrong and causes a crash

B Slider value range is incorrect

C sliderValue is not a @State variable, so changes are not tracked

D Slider value is not connected to the Text view

💡 Hint

Check how SwiftUI tracks changes in variables.

Without @State, SwiftUI does not track changes to sliderValue, so the UI does not update when the slider moves.

🧠 Conceptual

expert

Accessibility for Slider in SwiftUI

Which approach best improves accessibility for a slider controlling volume in SwiftUI?

A Set slider range from 0 to 100 without labels

B Add .accessibilityLabel("Volume") and .accessibilityValue with current value description

C Use a Text label only, no accessibility modifiers needed

D Disable accessibility for the slider to avoid confusion

💡 Hint

Think about how screen readers describe controls.

Adding .accessibilityLabel and .accessibilityValue helps screen readers announce the slider purpose and current value clearly.