Props passing in React Native - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are props in React Native?

Props are inputs to React components. They are used to pass data from a parent component to a child component, like giving instructions or information.

beginner

How do you pass a prop named title with value "Hello" to a component Greeting?

You write: <Greeting title="Hello" />. This sends the string "Hello" as the prop named title to the Greeting component.

beginner

How does a child component access props in React Native?

The child component receives props as a function argument. For example: <code>function Greeting(props) { return &lt;Text&gt;{props.title}&lt;/Text&gt;; }</code>

intermediate

Can props be changed inside the child component?

No, props are read-only. The child component should not modify props. If you want to change data, use state or pass new props from the parent.

beginner

Why is props passing important in React Native?

Props allow components to be reusable and dynamic by letting parents send different data to children. This helps build flexible and organized apps.

How do you pass a number prop named count with value 5 to a component Counter?

A <Counter count=5 />

B <Counter count={5} />

C <Counter count='5' />

D <Counter count="5" />

Numbers must be passed inside curly braces in JSX. So count={5} passes the number 5, not a string.

Where do props come from in a React Native app?

A From the parent component

B From the device hardware

C From the child component itself

D From the React Native library

Props are passed down from parent components to child components to share data.

Which of these is the correct way to access a prop named name inside a functional component?

A props.name

B this.props.name

C state.name

D name.props

In functional components, props are received as a parameter and accessed with props.name.

Can a child component modify the props it receives?

A Only if you use useEffect

B Yes, props are mutable

C Only if you use setState

D No, props are read-only

Props are read-only and should never be changed by the child component.

What happens if you pass no props to a component expecting some?

A The parent component crashes

B The app crashes

C The component uses default props or undefined values

D The component automatically creates props

If no props are passed, the component may use default props or get undefined values, depending on how it is coded.

Explain how props are passed and used in React Native components.

Think about how you tell a friend what to do and how they listen.

Describe why props passing helps make React Native apps reusable and organized.

Imagine giving different instructions to the same toy to make it do different things.

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