Lifting state up in React Native - Build, Publish & Deploy

Build & Publish - Lifting state up

Performance Impact

Lifting state up in React Native means moving shared state to a common parent component. This helps avoid duplicated state and keeps UI consistent. However, it can cause more components to re-render when the state changes, which may reduce frame rates if not managed well. Typically, if you lift state too high, many child components update unnecessarily, causing jank or dropped frames below 60fps.

Memory use is usually stable, but excessive re-renders can increase CPU load and battery use. Keep state minimal and focused to maintain smooth UI and save battery life.

Optimization Tips

To keep your app running at 60fps when lifting state up:

• Use React.memo to prevent child components from re-rendering unless their props change.
• Split state into smaller pieces so only relevant parts update.
• Use useCallback and useMemo hooks to avoid recreating functions or values unnecessarily.
• Consider local state for UI elements that don't affect others.
• Profile with React DevTools to find and fix slow re-renders.

App Size and Startup Time

Lifting state up does not directly affect your app's bundle size or startup time. It is a code organization pattern inside React Native components. However, better state management can reduce bugs and improve maintainability, indirectly speeding up development and app stability.

iOS vs Android Differences

Lifting state up works the same way on both iOS and Android in React Native because it is a JavaScript pattern. The React Native bridge handles UI updates on both platforms similarly.

Performance differences come from native rendering engines: iOS uses UIKit/SwiftUI, Android uses native views (Jetpack Compose is for native Android apps, not React Native). Efficient state updates help both platforms maintain smooth 60fps animations.

Store Review Guidelines

There are no direct store guidelines about lifting state up. But good state management helps avoid crashes and UI bugs, which are critical for passing Apple App Store and Google Play reviews.

Ensure your app:

• Does not freeze or crash due to inefficient state updates.
• Maintains responsive UI for accessibility and usability.
• Follows platform UI guidelines for smooth user experience.

Self-Check: Slow Screen Load

If your app screen takes 5 seconds to load after lifting state up, likely issues are:

• Too much state lifted causing many components to re-render at once.
• Heavy computations or data fetching done synchronously in the parent component.
• Missing memoization causing unnecessary re-renders.

Check your component tree with React DevTools profiler. Optimize by splitting state, memoizing components, and moving expensive work outside render.

Key Result

Lifting state up improves UI consistency but can cause extra re-renders that reduce frame rate. Use memoization and split state to keep 60fps smoothness on both iOS and Android. This pattern does not affect app size but helps maintain stable, review-ready apps.

Practice

1. What is the main purpose of lifting state up in React Native?

easy

A. To create multiple independent states in child components

B. To move shared state to a common parent component so children can access it

C. To store state only inside child components without sharing

D. To avoid using props for data sharing between components

Solution

1. Step 1: Understand the concept of shared state

   Lifting state up means moving state to a common parent so multiple children can use it.

2. Step 2: Identify the purpose of lifting state up

   This helps keep data consistent and allows children to communicate through the parent.

3. Final Answer:

   To move shared state to a common parent component so children can access it -> Option B

4. Quick Check:

   Lifting state up = shared parent state [OK]

Hint: Shared data lives in parent to sync children easily [OK]

Common Mistakes:

• Thinking each child should have its own separate state
• Believing lifting state up removes the need for props
• Confusing lifting state up with component styling

2. Which of the following is the correct way to pass a state update function from a parent to a child component in React Native?

easy

A.

B.

C.

D.

Solution

1. Step 1: Identify what to pass as prop

   The parent passes a function to update state, not the state value or setState method directly.

2. Step 2: Choose the correct syntax

   Passing updateStateFunction as a prop is correct to allow child to call it.

3. Final Answer:

   <Child updateState={updateStateFunction} /> -> Option C

4. Quick Check:

   Pass update function as prop = <Child updateState={updateStateFunction} /> [OK]

Hint: Pass functions, not state or setState directly [OK]

Common Mistakes:

• Passing the entire state object instead of a function
• Passing setState method directly without binding
• Passing state value instead of update function

3. Given the code below, what will be the output when the button in Child is pressed?

function Parent() {
  const [count, setCount] = React.useState(0);
  return (
    <>
      <Child count={count} increment={() => setCount(count + 1)} />
      <Text>Count: {count}</Text>
    </>
  );
}

function Child({ count, increment }) {
  return <Button title={`Add`} onPress={increment} />;
}

medium

A. The app will crash due to incorrect state update

B. The count will always stay 0 regardless of button presses

C. The button will not respond to presses

D. The count displayed will increase by 1 each time the button is pressed

Solution

1. Step 1: Understand state and props flow

   The Parent holds the count state and passes it plus an increment function to Child.

2. Step 2: Analyze what happens on button press

   Pressing the button calls increment, which updates count by adding 1.

3. Final Answer:

   The count displayed will increase by 1 each time the button is pressed -> Option D

4. Quick Check:

   State update via lifted function increments count [OK]

Hint: Button calls parent's update function to increase count [OK]

Common Mistakes:

• Thinking count won't update because it's passed as prop
• Assuming setCount is not called correctly
• Confusing local and lifted state

4. Identify the error in this lifting state up example:

function Parent() {
  const [text, setText] = React.useState('');
  return <Child text={text} setText={setText()} />;
}

function Child({ text, setText }) {
  return <TextInput value={text} onChangeText={setText} />;
}

medium

A. setText is called immediately instead of passing the function

B. text state is not initialized properly

C. Child component should not receive setText as prop

D. TextInput should not use onChangeText prop

Solution

1. Step 1: Check how setText is passed as prop

   In Parent, setText={setText()} calls setText immediately instead of passing the function.

2. Step 2: Correct way to pass setText

   It should be setText={setText} to pass the function reference.

3. Final Answer:

   setText is called immediately instead of passing the function -> Option A

4. Quick Check:

   Pass function reference, not call it [OK]

Hint: Pass function, don't call it when passing as prop [OK]

Common Mistakes:

• Calling setState function instead of passing it
• Confusing state value with update function
• Ignoring React hooks rules

5. You have two sibling components, TemperatureInputCelsius and TemperatureInputFahrenheit, that need to share temperature data. How should you use lifting state up to keep both inputs in sync?

hard

A. Move the temperature state to their common parent and pass value and update functions as props

B. Keep separate states in each sibling and update independently

C. Store temperature state only in one sibling and let the other read it directly

D. Use global variables outside React components to share temperature

Solution

1. Step 1: Identify the need for shared state

   Both siblings need to reflect the same temperature, so state must be shared.

2. Step 2: Apply lifting state up

   Move temperature state to their common parent and pass it plus update functions down as props.

3. Step 3: Avoid incorrect approaches

   Separate states cause inconsistency; global variables break React's data flow.

4. Final Answer:

   Move the temperature state to their common parent and pass value and update functions as props -> Option A

5. Quick Check:

   Lift shared state to parent for syncing siblings [OK]

Hint: Parent holds shared state; siblings get props and update functions [OK]

Common Mistakes:

• Keeping separate states causing out-of-sync inputs
• Trying to share state via global variables
• Passing state only to one sibling