Redux is a predictable state container for JavaScript apps. It helps manage the state of an application in a consistent and predictable way. By centralizing the state, Redux makes it easier to debug and maintain applications, especially as they grow in complexity.
Prerequisites
Why Do We Use Redux?
- Manage State Consistently: Redux provides a single source of truth for the application state, ensuring that all components reflect the same state.
- Debugging and Testing: With Redux, state changes are predictable, making debugging and testing simpler.
- State Management: Redux makes it easier to manage the state in large applications, providing a clear structure and flow for state updates.
How Does Redux Work?
Redux works by maintaining a single state tree. When an action is dispatched, Redux processes the action and updates the state accordingly. This process ensures that the state is predictable and manageable.
Redux Data Flow :
- Initial State: The application starts with an initial state. This initial state represents the default state of your application before any actions have been dispatched.
- Actions/Dispatches: Actions are payloads of information that send data from the application to the Redux store. They are the only source of information for the store. Actions must have a type property that indicates the type of action being performed and can also include additional data.
- Reducers: Reducers are pure functions that specify how the application's state changes in response to actions. They take the current state and an action as arguments and return a new state. Reducers determine the next state of the app based on the action type and payload.
- Store: The Redux store holds the entire state of the application. It is created using the 'createStore' function and is responsible for managing the state, allowing access to the state via 'getState()', and enabling state updates via 'dispatch(action)'. The store also handles the subscription of listeners through 'subscribe(listener)'.
- Subscribe: Components subscribe to the store to get updates when the state changes. This subscription mechanism allows React components to automatically re-render when the part of the state they depend on changes. In a React-Redux application, the connect function or hooks like 'useSelector' and 'useDispatch' handle this subscription.
- Dispatch: When an action is dispatched, it is sent to the Redux store. The store forwards the action to the appropriate reducer, which processes the action and returns a new state. The store then updates its state and notifies all subscribed components of the change, making them re-render with the new state.
Approach to Integrate Redux with React
- Using 'connect' API: The traditional method using 'connect' from 'react-redux' to connect React components to the Redux store.
- Using Hooks: The modern approach uses React hooks like 'useSelector' and 'useDispatch' to interact with the Redux store.
Approach 1: Using connect API
The 'connect' function from 'react-redux' is used to connect a React component to the Redux store. It takes two arguments:
- mapStateToProps: A function that takes the state from the Redux store and maps it to the component's props.
- mapDispatchToProps: A function that takes the dispatch function and maps it to the component's props as action dispatchers.
Example: A React component using the 'connect' API from Redux to map state and dispatch to props for displaying and incrementing a counter.
import { connect } from 'react-redux';
import { increment } from './actions';
const Counter = ({ count, increment }) => (
<div>
<p>{count}</p>
<button onClick={increment}>Increment</button>
</div>
);
const mapStateToProps = state => ({
count: state.count
});
const mapDispatchToProps = {
increment
};
export default connect(mapStateToProps, mapDispatchToProps)(Counter);
Approach 2: Using Hooks
The hooks approach utilizes 'useSelector' to read data from the Redux store and 'useDispatch' to dispatch actions.
Example: A functional React component using Redux to display and increment a counter.
import { useSelector, useDispatch } from 'react-redux';
import { increment } from './actions';
const Counter = () => {
const count = useSelector(state => state.count);
const dispatch = useDispatch();
return (
<div>
<p>{count}</p>
<button onClick={() => dispatch(increment())}>Increment</button>
</div>
);
};
export default Counter;
Applying Redux to Build an Application
Simple Counter Application
Let's build a simple counter application to demonstrate state management with the Redux store, actions, reducers, and component integration using hooks. This example will guide you through setting up Redux in a React application and show how to connect React components to the Redux store using hooks. By the end, you'll have a functional counter app with a clear understanding of Redux's core principles.
Step 1: Create a React application using the following command
npx create-react-app my-redux-app
Step 2: Move into the project directory
cd my-redux-app
Step 3: Install Redux and React Redux
npm install redux react-redux
Folder Structure
Folder StructureUpdated Dependencies
dependencies : {
"react": "^18.2.0",
"react-dom": "^18.2.0",
"react-redux": "^8.0.0",
"redux": "^4.0.0",
"react-scripts": "5.0.1",
"web-vitals": "^2.1.4"
}
You will see a simple counter with a button. When you click the button, the counter will increment.
- Actions: In 'src/actions/index.js', we defined an action called increment with a type of 'INCREMENT'. Actions are plain JavaScript objects that describe the type of change needed in the state.
- Reducer: In 'src/reducers/index.js', we created a reducer function called counterReducer. This function takes the current state and an action as arguments and returns a new state based on the action type. In our case, if the action type is 'INCREMENT', the reducer increases the count by 1.
- Store: In 'src/index.js', we created a Redux store using createStore and passed the counterReducer to it. The store holds the entire state of the application.
- Provider: We wrapped the 'App' component with the 'Provider' component from 'react-redux'. This makes the Redux store available to any nested components that need to access the Redux state.
- Component Integration: In 'src/components/Counter.js', we used useSelector to read the count value from the Redux store and useDispatch to dispatch the increment action when the button is clicked. This way, the 'Counter' component is connected to the Redux store using React hooks.
Example: A simple counter application using React Redux to demonstrate state management with Redux store, actions, reducers, and component integration using hooks.
JavaScript
//store.js
import { createStore } from 'redux';
import rootReducer from './reducers';
const store = createStore(rootReducer);
export default store;
JavaScript
//reducers.js
const initialState = {
count: 0
};
const rootReducer = (state = initialState, action) => {
switch (action.type) {
case 'INCREMENT':
return {
...state,
count: state.count + 1
};
default:
return state;
}
};
export default rootReducer;
JavaScript
//App.js
import React from 'react';
import { Provider } from 'react-redux';
import store from './store';
import Counter from './Components/Counter';
const App = () => (
<Provider store={store}>
<Counter />
</Provider>
);
export default App;
JavaScript
//actions.js
export const increment = () => ({
type: 'INCREMENT'
});
JavaScript
//Counter.js
import React from 'react';
import { useSelector, useDispatch } from 'react-redux';
import { increment } from '../actions';
const Counter = () => {
const count = useSelector(state => state.count);
const dispatch = useDispatch();
return (
<div className="counter">
<p>{count}</p>
<button onClick={() => dispatch(increment())}>Increment</button>
</div>
);
};
export default Counter;
Output
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