Redux Toolkit setup in React Native - Practice Problems & Coding Challenges

Challenge - 5 Problems

📝 Syntax

intermediate

Identify the correct Redux Toolkit store setup

Which option correctly creates a Redux store using Redux Toolkit's configureStore with a single reducer named counter?

React Native

import { configureStore } from '@reduxjs/toolkit';
import counterReducer from './counterSlice';

const store = configureStore({
  reducer: {
    counter: counterReducer
  }
});

A const store = configureStore({ reducer: { counter: counterReducer } });

B const store = configureStore(counterReducer);

C const store = configureStore({ reducer: counterReducer });

D const store = configureStore({ reducers: { counter: counterReducer } });

💡 Hint

Remember that configureStore expects an object with a reducer property that is an object mapping slice names to reducers.

Option A correctly passes an object with a reducer property containing the counter slice reducer. Option A passes the reducer directly, which is invalid. Option A passes the reducer directly without wrapping in an object. Option A uses reducers instead of reducer, which is incorrect.

❓ ui_behavior

intermediate

Redux Toolkit slice initial state behavior

Given this slice setup, what is the initial value of state.value when the app starts?

React Native

import { createSlice } from '@reduxjs/toolkit';

const counterSlice = createSlice({
  name: 'counter',
  initialState: { value: 10 },
  reducers: {
    increment: state => { state.value += 1; }
  }
});

A 0

B undefined

C null

D 10

💡 Hint

Look at the initialState property inside the slice.

The initialState is set to an object with value: 10, so the initial state.value is 10.

❓ lifecycle

advanced

When does Redux Toolkit's createSlice reducer get called?

In a React Native app using Redux Toolkit, when is the reducer function inside createSlice called?

A Only when the store is created

B Only once during app initialization

C Every time an action matching the slice's reducers is dispatched

D When the React component mounts

💡 Hint

Reducers respond to dispatched actions to update state.

Reducers created by createSlice run every time an action matching their name is dispatched to update the state accordingly.

❓ navigation

advanced

Connecting Redux store to React Native app

Which option correctly wraps the React Native app with the Redux Provider to make the store available?

React Native

import { Provider } from 'react-redux';
import store from './store';
import App from './App';

A <Provider store={store}><App /></Provider>

B <App><Provider store={store} /></App>

C <App store={store} />

D <Provider><App store={store} /></Provider>

💡 Hint

The Provider must wrap the entire app component tree.

Option A correctly wraps App inside Provider passing the store as a prop. Other options either pass the store incorrectly or do not wrap the app properly.

🔧 Debug

expert

Why does dispatching an action not update state?

Given this slice and store setup, why does dispatching increment() not update the UI?

React Native

import { createSlice, configureStore } from '@reduxjs/toolkit';

const counterSlice = createSlice({
  name: 'counter',
  initialState: { value: 0 },
  reducers: {
    increment: state => { state.value += 1; }
  }
});

const store = configureStore({
  reducer: counterSlice.reducer
});

// In component
// dispatch(counterSlice.actions.increment());
// useSelector(state => state.counter.value);

A The increment reducer mutates state directly, which is not allowed

B The store reducer is not an object with slice name keys, so state shape is incorrect

C The action is not dispatched correctly because increment is not exported

D The initialState is missing, so state is undefined

💡 Hint

Check how the store reducer is configured and how the state is accessed in useSelector.

The store reducer is set directly to the slice reducer function, so the state shape is just the value object. But the component tries to access state.counter.value, which is undefined. The reducer should be passed as an object with key 'counter' to match the state shape.

Practice

1. What is the main purpose of configureStore in Redux Toolkit?

easy

A. To create the Redux store with reducers and middleware setup automatically

B. To dispatch actions to update the store

C. To connect React components to the Redux store

D. To define action creators manually

Solution

1. Step 1: Understand configureStore role

   configureStore is a Redux Toolkit function that simplifies creating the Redux store by automatically combining reducers and adding middleware.

2. Step 2: Differentiate from other Redux tasks

   Dispatching actions and connecting components are done elsewhere, not by configureStore.

3. Final Answer:

   To create the Redux store with reducers and middleware setup automatically -> Option A

4. Quick Check:

   configureStore creates store [OK]

Hint: Remember: configureStore builds the store, not dispatch or connect [OK]

Common Mistakes:

• Confusing store creation with dispatching actions
• Thinking configureStore connects React components
• Assuming manual action creators are needed here

2. Which of the following is the correct syntax to create a Redux store using Redux Toolkit?

easy

A. const store = createStore(rootReducer);

B. const store = configureStore(rootReducer);

C. const store = configureStore({ reducer: rootReducer });

D. const store = new Store(rootReducer);

Solution

1. Step 1: Recall Redux Toolkit store creation syntax

   Redux Toolkit uses configureStore with an object argument containing the reducer key.

2. Step 2: Identify correct usage

   const store = configureStore({ reducer: rootReducer }); correctly passes an object with reducer: rootReducer. Options A and C use old or invalid syntax. const store = configureStore(rootReducer); passes reducer directly without an object, which is incorrect.

3. Final Answer:

   const store = configureStore({ reducer: rootReducer }); -> Option C

4. Quick Check:

   configureStore expects an object with reducer [OK]

Hint: Use configureStore({ reducer: ... }) syntax exactly [OK]

Common Mistakes:

• Passing reducer directly instead of inside an object
• Using createStore instead of configureStore
• Trying to instantiate Store with new keyword

3. Given this Redux Toolkit slice setup, what will be the initial state of the store?

import { configureStore, createSlice } from '@reduxjs/toolkit';

const counterSlice = createSlice({
  name: 'counter',
  initialState: { value: 10 },
  reducers: {
    increment: state => { state.value += 1; }
  }
});

const store = configureStore({ reducer: { counter: counterSlice.reducer } });

console.log(store.getState());

medium

A. { counter: { value: 0 } }

B. {}

C. { value: 10 }

D. { counter: { value: 10 } }

Solution

1. Step 1: Identify initialState in slice

   The slice defines initialState: { value: 10 } for the counter.

2. Step 2: Understand store state shape

   The store combines reducers under the key counter, so the state shape is { counter: { value: 10 } }.

3. Final Answer:

   { counter: { value: 10 } } -> Option D

4. Quick Check:

   Initial state matches slice's initialState under reducer key [OK]

Hint: Initial state is inside reducer key in store state [OK]

Common Mistakes:

• Ignoring reducer key nesting in state
• Assuming initial value is 0 by default
• Confusing slice state with root state shape

4. Identify the error in this Redux Toolkit store setup code:

import { configureStore } from '@reduxjs/toolkit';

const store = configureStore(reducer: rootReducer);

export default store;

medium

A. Missing curly braces around the reducer argument object

B. Using configureStore instead of createStore

C. rootReducer should be a string, not a variable

D. Export statement is incorrect

Solution

1. Step 1: Check configureStore argument syntax

   configureStore expects an object argument, so the reducer must be inside curly braces: { reducer: rootReducer }.

2. Step 2: Verify other parts

   Using configureStore is correct. rootReducer is a variable, which is valid. Export statement is fine.

3. Final Answer:

   Missing curly braces around the reducer argument object -> Option A

4. Quick Check:

   configureStore({ reducer: ... }) needs braces [OK]

Hint: Always pass an object with reducer key to configureStore [OK]

Common Mistakes:

• Passing reducer directly without braces
• Confusing configureStore with createStore
• Thinking export default is wrong here

5. You want to connect your React Native app to Redux using Redux Toolkit. Which is the correct way to wrap your app component to provide the store? A) <Provider store={store}><App /></Provider> B) <StoreProvider store={store}><App /></StoreProvider> C) <ReduxProvider store={store}><App /></ReduxProvider> D) <App store={store} />

hard

A.

B.

C.

D.

Solution

1. Step 1: Identify the correct provider component

   Redux Toolkit uses the Provider component from react-redux to supply the store to the app.

2. Step 2: Confirm correct usage

   The Provider wraps the root App component with the store prop. Other options use incorrect or nonexistent components.

3. Final Answer:

   <Provider store={store}><App /></Provider> -> Option B

4. Quick Check:

   Use Provider from react-redux to connect store [OK]

Hint: Wrap app in for Redux connection [OK]

Common Mistakes:

• Using wrong provider component names
• Passing store as a prop directly to App
• Forgetting to wrap the app at all