Switch and checkbox patterns in React Native - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Switch component from React Native.

React Native

import { [1] } from 'react-native';

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

ASwitch

BButton

CTextInput

DView

Attempts:

3 left

💡 Hint

Common Mistakes

Importing Button instead of Switch.

Forgetting to import Switch at all.

The Switch component is imported from react-native to create toggle switches.

2fill in blank

medium

Complete the code to set the initial state for a checkbox using React useState hook.

React Native

const [isChecked, [1]] = React.useState(false);

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

AsetChecked

BsetIsChecked

CtoggleChecked

DcheckedSetter

Attempts:

3 left

💡 Hint

Common Mistakes

Using a setter name that does not match the state variable.

Using a name that does not start with 'set'.

The setter function for isChecked state is conventionally named setIsChecked.

3fill in blank

hard

Fix the error in the Switch component to update the state when toggled.

React Native

<Switch value={isEnabled} onValueChange=[1] />

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

AtoggleIsEnabled()

BsetIsEnabled

C(value) => setIsEnabled(value)

D() => setIsEnabled(!isEnabled)

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the setter function directly without argument.

Calling the setter function immediately instead of passing a function.

The onValueChange handler receives the new value and should update the state accordingly using (value) => setIsEnabled(value).

4fill in blank

hard

Fill both blanks to create a checkbox using a Pressable and a conditional checkmark.

React Native

const [checked, setChecked] = React.useState(false);

<Pressable onPress={() => setChecked([1])}>
  {checked && <Text>[2]</Text>}
</Pressable>

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

A!checked

Bchecked

C✓

DX

Attempts:

3 left

💡 Hint

Common Mistakes

Setting state to true always instead of toggling.

Using wrong symbol for checkmark.

Pressing toggles the checked state by setting it to the opposite (!checked). The checkmark symbol '✓' is shown when checked is true.

5fill in blank

hard

Fill all three blanks to create a controlled Switch with label and accessibility.

React Native

const [isOn, setIsOn] = React.useState(false);

<View accessible accessibilityLabel=[1]>
  <Text>[2]</Text>
  <Switch value={isOn} onValueChange=[3] />
</View>

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

A"Toggle setting"

B"Enable feature"

C(value) => setIsOn(value)

D() => setIsOn(!isOn)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-descriptive accessibility label.

Not updating state correctly in onValueChange.

The accessibilityLabel describes the switch for screen readers, so use a descriptive string like "Toggle setting". The label text should describe the switch, e.g. "Enable feature". The onValueChange handler updates the state with the new value.

Practice

1. What is the main purpose of a Switch component in React Native?

easy

A. To toggle between two states like ON and OFF

B. To select multiple options from a list

C. To input text from the user

D. To display images in a gallery

Solution

1. Step 1: Understand the Switch component

   A Switch is a UI element that lets users toggle between two states, usually ON or OFF.

2. Step 2: Compare with other components

   Checkboxes allow multiple selections, text inputs accept text, and image galleries display images, so these do not match the Switch's purpose.

3. Final Answer:

   To toggle between two states like ON and OFF -> Option A

4. Quick Check:

   Switch toggles states = B [OK]

Hint: Switch means ON/OFF toggle, not multiple selections [OK]

Common Mistakes:

• Confusing Switch with Checkbox
• Thinking Switch accepts text input
• Assuming Switch displays images

2. Which of the following is the correct way to declare a controlled Switch component in React Native?

easy

A. setIsOn(!isOn)} />

B. setIsOn(!isOn)} />

C. setIsOn(!isOn)} />

D. setIsOn(!isOn)} />

Solution

1. Step 1: Recall Switch props in React Native

   The Switch component uses value to set its state and onValueChange as the event handler for toggling.

2. Step 2: Identify correct syntax

   Options using checked or onChange are incorrect because React Native Switch does not use these props.

3. Final Answer:

   <Switch value={isOn} onValueChange={() => setIsOn(!isOn)} /> -> Option D

4. Quick Check:

   Switch uses value and onValueChange = C [OK]

Hint: Switch uses value and onValueChange props [OK]

Common Mistakes:

• Using checked instead of value
• Using onChange instead of onValueChange
• Mixing HTML input props with React Native Switch

3. What will be the output on the screen after running this React Native code snippet?

const [checked, setChecked] = React.useState(false);

return (
  <CheckBox
    value={checked}
    onValueChange={() => setChecked(!checked)}
  />
);

If the user taps the checkbox once, what is the new value of checked?

medium

A. false

B. true

C. undefined

D. null

Solution

1. Step 1: Initial state value

   The state variable checked starts as false.

2. Step 2: Effect of tapping checkbox

   The onValueChange toggles checked to its opposite, so it becomes true after one tap.

3. Final Answer:

   true -> Option B

4. Quick Check:

   Toggle false once = true [OK]

Hint: Tapping toggles boolean state from false to true [OK]

Common Mistakes:

• Assuming state stays false after tap
• Confusing value prop with event
• Thinking onValueChange returns new value

4. Identify the error in this React Native code for a controlled Switch:

const [isEnabled, setIsEnabled] = React.useState(false);

return (
  <Switch
    value={isEnabled}
    onChange={() => setIsEnabled(!isEnabled)}
  />
);

medium

A. Using value instead of checked

B. Missing initial state declaration

C. Using onChange instead of onValueChange

D. Not importing React

Solution

1. Step 1: Check event handler prop

   The Switch component uses onValueChange to handle toggle events, not onChange.

2. Step 2: Verify other parts

   The initial state is declared, value is correct, and React import is assumed correct.

3. Final Answer:

   Using onChange instead of onValueChange -> Option C

4. Quick Check:

   Switch needs onValueChange, not onChange [OK]

Hint: Switch uses onValueChange, not onChange [OK]

Common Mistakes:

• Using onChange event instead of onValueChange
• Confusing value and checked props
• Forgetting to declare state

5. You want to create a list of three checkboxes in React Native where only one can be selected at a time (like radio buttons). Which approach correctly implements this behavior?

hard

A. Use three CheckBox components sharing one state variable that stores the selected option

B. Use one CheckBox component and change its label dynamically

C. Use three CheckBox components each with its own boolean state variable

D. Use three Switch components each with independent state variables

Solution

1. Step 1: Understand single selection requirement

   Only one checkbox can be selected at a time, so all must share one state that tracks which is selected.

2. Step 2: Evaluate options

   Use three CheckBox components sharing one state variable that stores the selected option. This uses one state variable to store the selected option and updates it on selection, ensuring only one is selected. Options A and C use independent states allowing multiple selections. Use one CheckBox component and change its label dynamically uses only one checkbox, which cannot represent three options.

3. Final Answer:

   Use three CheckBox components sharing one state variable that stores the selected option -> Option A

4. Quick Check:

   Single selection needs shared state = D [OK]

Hint: Single selection means one state tracks selected checkbox [OK]

Common Mistakes:

• Giving each checkbox its own state allowing multiple selections
• Using Switch instead of CheckBox for selection list
• Trying to reuse one checkbox for multiple options