React Redux

Official React bindings for Redux.
Performant and flexible.

Table of Contents

• Installation
• React Native
• Quick Start
• API
  • <Provider store>
  • connect([mapStateToProps], [mapDispatchToProps], [mergeProps], [options])
• Troubleshooting
• License

Installation

npm install --save react-redux

React Redux requires React 0.13 or later.

React Native

What you get from react-redux is for React.
For React Native, import from react-redux/native instead.

Quick Start

React bindings for Redux embrace the idea of dividing “smart” and “dumb” components.

It is advisable that only top-level components of your app (such as route handlers, for example) are aware of Redux. Components below them should be “dumb” and receive all data via props.

	“Smart” Components	“Dumb” Components
Location	Top level, route handlers	Middle and leaf components
Aware of Redux	Yes	No
To read data	Subscribe to Redux state	Read data from props
To change data	Dispatch Redux actions	Invoke callbacks from props

“Dumb” components are unaware of Redux

Let’s say we have a <Counter /> “dumb” component with a number value prop, and an onIncrement function prop that it will call when user presses an “Increment” button:

import { Component } from 'react';

export default class Counter extends Component {
  render() {
    return (
      <button onClick={this.props.onIncrement}>
        {this.props.value}
      </button>
    );
  }
}

“Smart” components are connect()-ed to Redux

Here’s how we hook it up to the Redux Store.

We will use the connect() function provided by react-redux to turn a “dumb” Counter into a smart component. The connect() function lets you specify which exact state from the Redux store your component wants to track. This lets you subscribe on any level of granularity.

containers/CounterContainer.js

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

import Counter from '../components/Counter';
import { increment } from '../actionsCreators';

// Which part of the Redux global state does our component want to receive as props?
function mapStateToProps(state) {
  return {
    value: state.counter
  };
}

// Which action creators does it want to receive by props?
function mapDispatchToProps(dispatch) {
  return {
    onIncrement: () => dispatch(increment())
  };
}

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

// You can also pass an object instead of defining `mapDispatchToProps`:
// export default connect(mapStateToProps, CounterActionCreators)(Counter);

// Or you can pass `dispatch` down as a prop if you omit `mapDispatchToProps`:
// export default connect(mapStateToProps)(Counter);

// See more recipes in detailed connect() examples below.

Whether to put the connect() call in the same file as the “dumb” component, or separately, is up to you.
Ask yourself whether you’d want to reuse this component but bind it to different data, or not.

Nesting

You can have many connect()-ed components in your app at any depth, and you can even nest them. It is, however, preferable that you try to only connect() top-level components such as route handlers, so the data flow in your application stays predictable.

Support for Decorators

You might have noticed that we used parens twice when calling connect(). This is called partial application, and it lets people use ES7’s proposed decorator syntax:

// Unstable syntax! It might change or break in production.
@connect(mapStateToProps)
export default class CounterContainer { ... }

Don’t forget decorators are experimental! They desugar to function calls anyway as the example above demonstrates.

Additional Flexibility

This is the most basic usage, but connect() supports many other patterns: just passing the vanilla dispatch() function down, binding multiple action creators, passing them in an actions prop, selecting parts of state and binding action creators depending on props, and so on. Check out the connect() docs below to learn more.

Injecting Redux Store

Finally, how do we actually hook it up to the Redux store? We need to create the store somewhere at the root of our component hierarchy. For client apps, the root component is a good place. For server rendering, you can do this in the request handler.

The trick is to wrap the whole view hierarchy into a <Provider>{() => ... }</Provider> where Provider is imported from react-redux. One gotcha is that the child of Provider must be a function. This is to work around an issue about how context (undocumented feature we have to rely on to pass Redux data to components below) works in React 0.13. In React 0.14, you will be able to put your view hierarchy in <Provider> without wrapping it into a function.

import { Component } from 'react';
import { Provider } from 'react-redux';

class App extends Component {
  render() {
    // ...
  }
}

const targetEl = document.getElementById('root');

React.render((
  <Provider store={store}>
    {() => <App />}
  </Provider>
), targetEl);

API

<Provider store>

Makes the Redux store available to the connect() calls in the component hierarchy below. Normally, you can’t use connect() without wrapping the root component in <Provider>. (If you really need to, you can manually pass store as a prop to every connect()ed component, but we only recommend to do this for stubbing store in unit tests, or in non-fully-React codebases. Normally, you should just use <Provider>.)

Props

• store: (Redux Store): The single Redux store in your application.
• children: (Function): Unlike most React components, <Provider> accepts a function as a child with your root component. This is a temporary workaround for a React 0.13 context issue, which will be fixed when React 0.14 comes out.

Example

Vanilla React

React.render(
  <Provider store={store}>
    {() => <MyRootComponent />}
  </Provider>,
  rootEl
);

React Router 0.13

Router.run(routes, Router.HistoryLocation, (Handler, routerState) => { // note "routerState" here
  React.render(
    <Provider store={store}>
      {() => <Handler routerState={routerState} />} // note "routerState" here: important to pass it down
    </Provider>,
    document.getElementById('root')
  );
});

React Router 1.0

React.render(
  <Provider store={store}>
    {() => <Router history={history}>...</Router>}
  </Provider>,
  targetEl
);

connect([mapStateToProps], [mapDispatchToProps], [mergeProps], [options])

Connects a React component to a Redux store.

It does not modify the component class passed to it.
Instead, it returns a new, connected component class, for you to use.

Arguments

• [mapStateToProps(state, [ownProps]): stateProps] (Function): If specified, the component will subscribe to Redux store updates. Any time it updates, mapStateToProps will be called. Its result must be a plain object, and it will be merged into the component’s props. If you omit it, the component will not be subscribed to the Redux store. If ownProps is specified as a second argument, then mapStateToProps will be re-invoked whenever the component receives new props.

• [mapDispatchToProps(dispatch, [ownProps]): dispatchProps] (Object or Function): If an object is passed, each function inside it will be assumed to be a Redux action creator. An object with the same function names, but bound to a Redux store, will be merged into the component’s props. If a function is passed, it will be given dispatch. It’s up to you to return an object that somehow uses dispatch to bind action creators in your own way. (Tip: you may use the bindActionCreators() helper from Redux.) If you omit it, the default implementation just injects dispatch into your component’s props. If ownProps is specified as a second argument, then mapDispatchToProps will be re-invoked whenever the component receives new props.

• [mergeProps(stateProps, dispatchProps, ownProps): props] (Function): If specified, it is passed the result of mapStateToProps(), mapDispatchToProps(), and the parent props. The plain object you return from it will be passed as props to the wrapped component. You may specify this function to select a slice of the state based on props, or to bind action creators to a particular variable from props. If you omit it, Object.assign({}, ownProps, stateProps, dispatchProps) is used by default.

• [options] (Object) If specified, further customizes the behavior of the connector.

  • [pure] (Boolean): If true, implements shouldComponentUpdate and shallowly compares the result of mergeProps, preventing unnecessary updates, assuming that the component is a “pure” component and does not rely on any input or state other than its props and the selected Redux store’s state. Defaults to true.

Returns

A React component class that injects state and action creators into your component according to the specified options.

Remarks

• It needs to be invoked two times. The first time with its arguments described above, and a second time, with the component: connect(mapStateToProps, mapDispatchToProps, mergeProps)(MyComponent).

• It does not modify the passed React component. It returns a new, connected component, that you should use instead.

• The mapStateToProps function takes a single argument of the entire Redux store’s state and returns an object to be passed as props. It is often called a selector. Use reselect to efficiently compose selectors and compute derived data.

• To use connect(), the root component of your app must be wrapped into <Provider>{() => ... }</Provider> before being rendered. You may also pass store as a prop to the connect()ed component, but it's not recommended, because it's just too much trouble. Only do this for non-fully-React codebases or to stub the store in a unit test.

Examples

Inject just dispatch and don't listen to store

export default connect()(TodoApp);

Inject dispatch and every field in the global state

Don’t do this! It kills any performance optimisations because TodoApp will rerender after every action.
It’s better to have more granular connect() on several components in your view hierarchy that each only
listen to a relevant slice of the state.

export default connect(state => state)(TodoApp);

Inject dispatch and todos

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

export default connect(mapStateToProps)(TodoApp);

Inject todos and all action creators (addTodo, completeTodo, ...)

import * as actionCreators from './actionCreators';

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

export default connect(mapStateToProps, actionCreators)(TodoApp);

Inject todos and all action creators (addTodo, completeTodo, ...) as actions

import * as actionCreators from './actionCreators';
import { bindActionCreators } from 'redux';

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

function mapDispatchToProps(dispatch) {
  return { actions: bindActionCreators(actionCreators, dispatch) };
}

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

Inject todos and a specific action creator (addTodo)

import { addTodo } from './actionCreators';
import { bindActionCreators } from 'redux';

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

function mapDispatchToProps(dispatch) {
  return bindActionCreators({ addTodo }, dispatch);
}

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

Inject todos, todoActionCreators as todoActions, and counterActionCreators as counterActions

import * as todoActionCreators from './todoActionCreators';
import * as counterActionCreators from './counterActionCreators';
import { bindActionCreators } from 'redux';

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

function mapDispatchToProps(dispatch) {
  return {
    todoActions: bindActionCreators(todoActionCreators, dispatch),
    counterActions: bindActionCreators(counterActionCreators, dispatch)
  };
}

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

Inject todos, and todoActionCreators and counterActionCreators together as actions

import * as todoActionCreators from './todoActionCreators';
import * as counterActionCreators from './counterActionCreators';
import { bindActionCreators } from 'redux';

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

function mapDispatchToProps(dispatch) {
  return {
    actions: bindActionCreators(Object.assign({}, todoActionCreators, counterActionCreators), dispatch)
  };
}

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

Inject todos, and all todoActionCreators and counterActionCreators directly as props

import * as todoActionCreators from './todoActionCreators';
import * as counterActionCreators from './counterActionCreators';
import { bindActionCreators } from 'redux';

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

function mapDispatchToProps(dispatch) {
  return bindActionCreators(Object.assign({}, todoActionCreators, counterActionCreators), dispatch);
}

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

Inject todos of a specific user depending on props

import * as actionCreators from './actionCreators';

function mapStateToProps(state, ownProps) {
  return { todos: state.todos[ownProps.userId] };
}

export default connect(mapStateToProps)(TodoApp);

Inject todos of a specific user depending on props, and inject props.userId into the action

import * as actionCreators from './actionCreators';

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

function mergeProps(stateProps, dispatchProps, ownProps) {
  return Object.assign({}, ownProps, {
    todos: stateProps.todos[ownProps.userId],
    addTodo: (text) => dispatchProps.addTodo(ownProps.userId, text)
  });
}

export default connect(mapStateToProps, actionCreators, mergeProps)(TodoApp);

Troubleshooting

Make sure to check out Troubleshooting Redux first.

My views aren’t updating!

See the link above. In short,

• Reducers should never mutate state, they must return new objects, or React Redux won’t see the updates.
• Make sure you either bind action creators with the mapDispatchToProps argument to connect() or with the bindActionCreators() method, or that you manually call dispatch(). Just calling your MyActionCreators.addTodo() function won’t work because it just returns an action, but does not dispatch it.

My views aren’t updating on route change with React Router 0.13

If you’re using React Router 0.13, you might bump into this problem. The solution is simple: whenever you use <RouteHandler> or the Handler provided by Router.run, pass the router state to it.

Root view:

Router.run(routes, Router.HistoryLocation, (Handler, routerState) => { // note "routerState" here
  React.render(
    <Provider store={store}>
      {() => <Handler routerState={routerState} />} // note "routerState" here
    </Provider>,
    document.getElementById('root')
  );
});

Nested view:

render() {
  // Keep passing it down
  return <RouteHandler routerState={this.props.routerState} />;
}

Conveniently, this gives your components access to the router state! You can also upgrade to React Router 1.0 which shouldn’t have this problem. (Let us know if it does!)

My views aren’t updating when something changes outside of Redux

If your views depend on global state or React “context”, you might find that views decorated with connect() will fail to update.

This is because connect() implements shouldComponentUpdate by default, assuming that your component will produce the same results given the same props and state. This is a similar concept to React’s PureRenderMixin.

The best solution to this is to make sure that your components are pure and pass any external state to them via props. This will ensure that your views do not re-render unless they actually need to re-render and will greatly speed up your application.

If that's not practical for whatever reason (for example, if you’re using a library that depends heavily on React context), you may pass the pure: false option to connect():

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

export default connect(mapStateToProps, null, null, {
  pure: false
})(TodoApp);

This will remove the assumption that TodoApp is pure and cause it to update whenever its parent component renders. Note that this will make your application less performant, so only do this if you have no other option.

Could not find "store" in either the context or props

If you have context issues,

1. Make sure you don’t have a duplicate instance of React on the page.
2. Make sure you didn’t forget to wrap your root component in <Provider>.
3. If you use React Router, something like <Provider>{() => router}</Provider> won’t work. Due to the way context works in React 0.13, it’s important that the <Provider> children are created inside that function. Just referencing an outside variable doesn’t do the trick. Instead of <Provider>{() => router}</Provider>, write <Provider>{() => createRouter()}</Provider> where createRouter() is a function that actually creates (and returns) the router.

Invariant Violation: addComponentAsRefTo(...): Only a ReactOwner can have refs. This usually means that you’re trying to add a ref to a component that doesn’t have an owner

If you’re using React for web, this usually means you have a duplicate React. Follow the linked instructions to fix this.

If you’re using React Native, make sure you’re importing react-redux/native both for <Provider> and any connect() call. Importing from react-redux will not work on React Native.

License

MIT