api.md

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 (ReactElement) The root of your component hierarchy.

Example

Vanilla React

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

React Router

ReactDOM.render(
  <Provider store={store}>
    <Router history={history}>
      <Route path="/" component={App}>
        <Route path="foo" component={Foo}/>
        <Route path="bar" component={Bar}/>
      </Route>
    </Router>
  </Provider>,
  document.getElementById('root')
)

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, its value will be the props passed to your component, and mapStateToProps will be additionally re-invoked whenever the component receives new props (e.g. if props received from a parent component have shallowly changed, and you use the ownProps argument, mapStateToProps is re-evaluated).

  Note: in advanced scenarios where you need more control over the rendering performance, mapStateToProps() can also return a function. In this case, that function will be used as mapStateToProps() for a particular component instance. This allows you to do per-instance memoization. You can refer to #279 and the tests it adds for more details. Most apps never need this.

• [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 with every action creator wrapped into a dispatch call so they may be invoked directly, 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, its value will be the props passed to your component, and mapDispatchToProps will be re-invoked whenever the component receives new props.

  Note: in advanced scenarios where you need more control over the rendering performance, mapDispatchToProps() can also return a function. In this case, that function will be used as mapDispatchToProps() for a particular component instance. This allows you to do per-instance memoization. You can refer to #279 and the tests it adds for more details. Most apps never need this.

• [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 = true] (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.
  • [withRef = false] (Boolean): If true, stores a ref to the wrapped component instance and makes it available via getWrappedInstance() method. Defaults to false.

Note: ownProps is not passed to mapStateToProps and mapDispatchToProps if formal definition of the function contains one mandatory parameter (function has length 1). For example, function defined like below won't receive ownProps as the second argument.

function mapStateToProps(state) {
  console.log(state); // state
  console.log(arguments[1]); // undefined
}

const mapStateToProps = (state, ownProps = {}) => {
  console.log(state); // state
  console.log(ownProps); // undefined
}

Functions with no mandatory parameters or two parameters will receive ownProps.

const mapStateToProps = (state, ownProps) => {
  console.log(state); // state
  console.log(ownProps); // ownProps
}

function mapStateToProps() {
  console.log(arguments[0]); // state
  console.log(arguments[1]); // ownProps
}

const mapStateToProps = (...args) => {
  console.log(args[0]); // state
  console.log(args[1]); // ownProps
}

Returns

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

Static Properties

• WrappedComponent (Component): The original component class passed to connect().

Static Methods

All the original static methods of the component are hoisted.

Instance Methods

getWrappedInstance(): ReactComponent

Returns the wrapped component instance. Only available if you pass { withRef: true } as part of the connect()’s fourth options argument.

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.

Examples

Inject just dispatch and don't listen to store

export default connect()(TodoApp)

Inject all action creators (addTodo, completeTodo, ...) without subscribing to the store

import * as actionCreators from './actionCreators'

export default connect(null, actionCreators)(TodoApp)

Inject dispatch and every field in the global state

Don’t do this! It kills any performance optimizations 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

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)