Getting started with react-redux

Remarks#

React Redux is a library which provides React bindings for Redux.

React components aware of the Redux store are called “Containers”, “Smart Components” or “Higher Order Component” (HOC). Such components, to use Redux, need to:

• Subscribe to the store to get updates from Redux store
• Dispatch actions

Doing this by hand would imply using store.subscribe and store.dispatch(action) in React containers.

React Redux simplifies the binding between the Redux store and a React container component by way of the connect function, which maps Redux state properties and Action creators to the component’s props.

connect is a function that creates a higher order component. Connect accepts 3 functions (mapStateToProps, mapDispatchToProps, mergeProps) and returns a container component, that wraps the original component to make turn it into a “connected” component:

import { connect } from 'react-redux';

const Customers = { ... };
const mapStateToProps = (state) => { ... }
const mapDispatchToProps = (dispatch) => { ... }

export default connect(mapStateToProps, mapDispatchToProps)(Customers);

See the examples section for a complete example.

Since all container componenents need to access the Redux store, the recommended way is to use a special <Provider> component of React Redux, which passes the store to all the children components (internally using React context).

Official documentation: https://redux.js.org/docs/basics/UsageWithReact.html

GitHub repo: https://github.com/reactjs/react-redux

Versions#

Installation or Setup

Using redux directly with react might seem little difficult, As for every component you want to update when store changes, you have to subscribe that component to the redux store

React Redux takes care of all these and makes it really easy to write components that can request the data it needs from redux store and be notified Only when those data changes., This allows us to write really effective components.

To install react-redux all you have to do is run this npm command

npm install --save react-redux

And you’re done.

Note: React Redux is dependent on

• React (Version 0.14 or later) and
• Redux

Complete example

Suppose we have container “CustomersContainer” which connects a “Customers” dumb component to the Redux store.

In index.js:

import { Component }, React from 'react';
import { render } from 'react-dom';
import { Provider } from 'react-redux';
import { createStore } from 'redux';
import rootReducer from './redux/rootReducer';
import CustomersContainer from './containers/CustomersContainer';

let store = createStore(rootReducer);

render(
  <Provider store={store}>
    <CustomersContainer />
  </Provider>,
  document.getElementById('root')
);

In CustomersContainer:

import React, { Component } from 'react';
import { connect } from 'react-redux';

// Import action creators
import { fetchCustomers } from '../redux/actions';

// Import dumb component
import Customers from '../components/Customers';

// ES6 class declaration
class CustomersContainer extends Component {
  componentWillMount() {
    // Action fetchCustomers mapped to prop fetchCustomers
    this.props.fetchCustomers();
  }

  render() {
    return <Customers customers={this.props.customers} />;
  }
}

function mapStateToProps(state) {
  return {
    customers: state.customers
  };
}

// Here we use the shorthand notation for mapDispatchToProps
// it can be used when the props and action creators have the same name 
const CustomersContainer = connect(mapStateToProps, { fetchCustomers })(CustomersContainer);

export default CustomersContainer;

Hello World using React Redux

This guide assumes you have already installed react, redux, react-router and react-redux and have configured react, redux and react-router., If you haven’t, Please do so.

Note: While react-router in not a dependency of react-redux, It’s very likely that we will using it in our react application for routing and this makes it really easy for us to use react-redux.

FILENAME: app.js

'use strict';

import React from 'react';
import { render } from 'react-dom';
import { Router, Route, Link, browserHistory, IndexRoute } from 'react-router';
import { Provider } from 'react-redux';
import store from './stores';

render(
  (
    <Provider store={ store }>
      <Router history={ browserHistory }>
        {/* all the routes here */}
      </Router>
    </Provider>
  ),
  document.getElementById('app')
);

This file will make sense to most of you, What we’re doing here is getting the store from ./stores and passing it to all the routes using Higher Order Component Provider provided by react-redux.

This makes the store available throughout our application.

Now, let’s consider this scenario. We have a component UserComponent which gets the data from user reducer and has a button which when clicked updates the data in the store.

Application Structure

Our rootReducer has user reducer

const rootReducer = combineReducers({
    user: userReducer,
})
export default rootReducer;

Our userReducer looks like this

const default_state = {
  users: [],
  current_user: {
    name: 'John Doe',
    email: 'john.doe@gmail.com',
    gender: 'Male'
  },
  etc: {}
};

function userReducer( state=default_state, action ) {

  if ( action.type === "UPDATE_CURRENT_USER_DATA" ) {
    return Object.assign( {}, state, { current_user: Object.assign( {}, state.current_user, { [action.payload.field]: action.payload.value } ) } );
  }
  else {
    return state;
  }

}

export default userReducer;

And our actions file looks something like this

export function updateCurrentUserData( data ) {
  return {
    type: "UPDATE_CURRENT_USER_DATA",
    payload: data
  }
}

Finally, Lets work on our component

FILENAME: UserComponent.js

'use strict';

import React from 'react';
import { connect } from 'react-redux';
import * as Action from './actions';

let UserComponent = (props) => {

  let changeUserDetails = (field, value) => {
    // do nothing
  }

  return(
    <div>
      <h1>Hello { props.current_user.name }</h1>
      <p>Your email address is { props.current_user.email }</p>
      <div style={{ marginTop: 30 }}>
        <button onClick={ () => { changeUserDetails('name', 'Jame Smith') } }>Change Name</button>
        <button onClick={ () => { changeUserDetails('email', 'jane@gmail.com') } }>Change Email Address</button>
      </div>
    </div>
  )

}

export default UserComponent;

Of course this won’t work, As we haven’t connected it to the store yet.

In case you’re wondering, this is a stateless functional component, since we’re using redux and we don’t really need an internal state for our component, this is the right time to use it.

The connect method provided by react-redux takes in three parameters

mapStateToProps, mapDispatchToProps and the Component itself.

connect( mapStateToProps, mapDispatchToProps )(Component)

Let’s add connect to our component UserComponent along with mapStateToProps and mapDispatchToProps

And let’s also update our changeUserDetails function, so when called, It will dispatch an action to our reducers, and based on the type of action our reducer will kick in and make changes to the store, and once the store updated react-redux will re-render our component with the new data.

Sounds complicated? It really isn’t.

Our UserComponent.js will look like

'use strict';

import React from 'react';
import { connect } from 'react-redux';
import * as Action from './actions';

const mapStateToProps = ( state, ownProps ) => {
  return {
    current_user: state.user.current_user,
  }
}

const mapDispatchToProps = ( dispatch, ownProps ) => {
  return {
    updateCurrentUserData: (payload) => dispatch( Action.updateCurrentUserData(payload) ),
  }
}


let UserComponent = (props) => {

  let changeUserDetails = (field, value) => {
    props.updateCurrentUserData({ field: field, value: value });
  }

  return(
    <div>
      <h1>Hello { props.current_user.name }</h1>
      <p>Your email address is { props.current_user.email }</p>
      <div style={{ marginTop: 30 }}>
        <button onClick={ () => { changeUserDetails('name', 'Jame Smith') } }>Change Name</button>
        <button onClick={ () => { changeUserDetails('email', 'jane@gmail.com') } }>Change Email Address</button>
      </div>
    </div>
  )

}

const ConnectedUserComponent = connect(
  mapStateToProps,
  mapDispatchToProps
)(UserComponent)

export default ConnectedUserComponent;

What we did here is added

• mapStateToProps: This allows us to get the data from store and when that data changes, our component will be re-rendered with the new data.

  Our component will only re-render if the data our component is requesting changes in the store and not when any other data changes in the store.

• mapDispatchToProps: This allows us to dispatch actions to all the reducers from our component.. (could be any component), And based on the type of action, our userReducer will kick in and return a new state with the updated data.

• ConnectedUserComponent: Lastly, we connected our component to the store using the connect method by passing all the parameters and exported the connected component.

• We also updated our changeUserDetails function to call method on props and also pass in the data., And props in turn dispatches the method we called to all reducers.

NOTE:

• If we don’t return a new state from reducer, react-redux wont re-render our component.