Props passing in React Native - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What will be displayed by this component?

Consider this React Native component that receives a prop called name. What text will it show on the screen?

React Native

function Greeting(props) {
  return <Text>Hello, {props.name}!</Text>;
}

// Usage:
<Greeting name="Alice" />

A Error: props is undefined

B Hello, props.name!

C Hello, Alice!

D Hello, !

💡 Hint

Props are used to pass data from parent to child components.

The component uses props.name to show the passed value 'Alice'. So it displays 'Hello, Alice!'.

📝 Syntax

intermediate

Which option correctly passes multiple props?

You want to pass two props, title and count, to a component. Which usage is correct?

React Native

function Info(props) {
  return <Text>{props.title}: {props.count}</Text>;
}

A <Info title="Messages" count={5} />

B <Info title="Messages" count=5 />

C <Info title={"Messages"} count="5" />

D <Info title=Messages count=5 />

💡 Hint

Use curly braces for numbers and quotes for strings in JSX props.

Option A correctly passes a string prop with quotes and a number prop with curly braces.

❓ lifecycle

advanced

What happens if a prop changes in a functional component?

If a parent component passes a prop color to a child functional component, what happens when color changes?

A The child component re-renders with the new prop value.

B The child component ignores the change and keeps old value.

C The child component unmounts and remounts.

D The app crashes with an error.

💡 Hint

React updates components when props change to keep UI in sync.

React re-renders child components when their props change to update the UI accordingly.

🔧 Debug

advanced

Why does this component show 'undefined' for a prop?

This component tries to show props.message but displays 'undefined'. What is the likely cause?

React Native

function ShowMessage(props) {
  return <Text>{message}</Text>;
}

// Usage:
<ShowMessage message="Hi!" />

A The component must use state to show props.

B The prop 'message' was not passed from parent.

C React Native Text component cannot display props.

D The component uses 'message' instead of 'props.message'.

💡 Hint

Inside the component, you must access props with 'props.' prefix.

The code uses 'message' directly, which is undefined. It should use 'props.message' to access the prop.

🧠 Conceptual

expert

What is the main benefit of passing props in React Native?

Why do React Native components use props to receive data instead of using global variables?

A Props automatically update the database with new values.

B Props make components reusable and predictable by passing data explicitly.

C Props allow components to change global variables directly.

D Props prevent components from rendering multiple times.

💡 Hint

Think about how data flows in React apps and why explicit data passing is helpful.

Props let components receive data clearly from parents, making them reusable and easier to understand.

Practice

1. What is the main purpose of props in React Native components?

easy

A. To style components with CSS

B. To store internal state of a component

C. To pass data from a parent component to a child component

D. To handle user input events

Solution

1. Step 1: Understand the role of props

   Props are used to send data from a parent component down to its children, allowing dynamic content.

2. Step 2: Differentiate props from state and styling

   State holds internal data, styling is separate, and event handling is done via callbacks, not props alone.

3. Final Answer:

   To pass data from a parent component to a child component -> Option C

4. Quick Check:

   Props = Data passing from parent to child [OK]

Hint: Props always flow from parent to child components [OK]

Common Mistakes:

• Confusing props with state
• Thinking props handle styling
• Assuming props manage events directly

2. Which of the following is the correct way to pass a prop named title with value "Hello" to a component Greeting?

easy

A.

B.

C.

D.

Solution

1. Step 1: Recognize JSX prop syntax

   Props with string values must be passed inside quotes like title="Hello".

2. Step 2: Identify incorrect syntax

   Using curly braces without quotes expects a variable, missing quotes or equals sign is invalid.

3. Final Answer:

   <Greeting title="Hello" /> -> Option A

4. Quick Check:

   String props need quotes in JSX [OK]

Hint: Use quotes for string props in JSX [OK]

Common Mistakes:

• Omitting quotes around string values
• Using curly braces for plain strings
• Missing equals sign between prop and value

3. What will be displayed on the screen when this code runs?

function Welcome(props) {
  return {props.message};
}

export default function App() {
  return ;
}

medium

A. props.message

B. Error: message not defined

C. Welcome

D. Hi there!

Solution

1. Step 1: Identify prop usage in Welcome component

   The Welcome component receives message prop and displays it inside Text.

2. Step 2: Check what prop value is passed

   The App component passes message="Hi there!" to Welcome.

3. Final Answer:

   Hi there! -> Option D

4. Quick Check:

   Props value shown in child component [OK]

Hint: Props values appear where used inside child components [OK]

Common Mistakes:

• Printing the prop name instead of its value
• Expecting component name to display
• Assuming missing prop causes error

4. Identify the error in this code snippet:

function Button(props) {
  return {props.label};
}

export default function App() {
  return ;
}

medium

A. Missing quotes around string prop value

B. Incorrect component name

C. Text component cannot display props

D. Props cannot be passed to functional components

Solution

1. Step 1: Check prop syntax in App component

   The prop label is passed as label=ClickMe without quotes, which is invalid for strings.

2. Step 2: Understand correct JSX prop passing

   String values must be in quotes like label="ClickMe" or in curly braces if variable.

3. Final Answer:

   Missing quotes around string prop value -> Option A

4. Quick Check:

   String props need quotes in JSX [OK]

Hint: Always quote string props in JSX [OK]

Common Mistakes:

• Forgetting quotes around string props
• Thinking props can't be passed to functions
• Misunderstanding Text component usage

5. You want to create a reusable Profile component that shows a user's name and age. Which of these is the best way to pass props to make it flexible?

hard

A.

B.

C.

D.

Solution

1. Step 1: Check prop value types and syntax

   Strings like name should be in quotes; numbers like age should be passed as JavaScript expressions using curly braces.

2. Step 2: Evaluate each option

   <Profile name="Alice" age={30} /> correctly passes name as string and age as number. <Profile name={"Alice"} age="30" /> passes age as string which is less ideal. <Profile name=Alice age=30 /> misses quotes and braces. <Profile name={Alice} age={30} /> uses undefined variable Alice.

3. Final Answer:

   <Profile name="Alice" age={30} /> -> Option B

4. Quick Check:

   Strings in quotes, numbers in braces [OK]

Hint: Use quotes for strings, braces for numbers in props [OK]

Common Mistakes:

• Passing numbers as strings
• Omitting quotes for strings
• Using undefined variables without quotes