I have a react-redux container component that is created within a React Native Navigator component. I want to be able to pass the navigator as a prop to this container component so that after a button is pressed inside its presentational component, it can push an object onto the navigator stack.
I want to do this without needing to hand write all the boilerplate code that the react-redux container component gives me (and also not miss out on all the optimisations that react-redux would give me here too).
Example container component code:
const mapStateToProps = (state) => {
return {
prop1: state.prop1,
prop2: state.prop2
}
}
const mapDispatchToProps = (dispatch) => {
return {
onSearchPressed: (e) => {
dispatch(submitSearch(navigator)) // This is where I want to use the injected navigator
}
}
}
const SearchViewContainer = connect(
mapStateToProps,
mapDispatchToProps
)(SearchView)
export default SearchViewContainer
And I'd want to be able to call the component like this from within my navigator renderScene function:
<SearchViewContainer navigator={navigator}/>
In the container code above, I'd need to be able to access this passed prop from within the mapDispatchToProps function.
I don't fancy storing the navigator on the redux state object and don't want to pass the prop down to the presentational component.
Is there a way I can pass in a prop to this container component? Alternatively, are there any alternative approaches that I'm overlooking?
Thanks.
mapStateToProps and mapDispatchToProps both take ownProps as the second argument.
[mapStateToProps(state, [ownProps]): stateProps] (Function):
[mapDispatchToProps(dispatch, [ownProps]): dispatchProps] (Object or Function):
For reference
You can pass in a second argument to mapStateToProps(state, ownProps) which will give you access to the props passed into the component in mapStateToProps
There's a few gotchas when doing this with typescript, so here's an example.
One gotcha was when you are only using dispatchToProps (and not mapping any state props), it's important to not omit the state param, (it can be named with an underscore prefix).
Another gotcha was that the ownProps param had to be typed using an interface containing only the passed props - this can be achieved by splitting your props interface into two interfaces, e.g.
interface MyComponentOwnProps {
value: number;
}
interface MyComponentConnectedProps {
someAction: (x: number) => void;
}
export class MyComponent extends React.Component<
MyComponentOwnProps & MyComponentConnectedProps
> {
....// component logic
}
const mapStateToProps = (
_state: AppState,
ownProps: MyComponentOwnProps,
) => ({
value: ownProps.value,
});
const mapDispatchToProps = {
someAction,
};
export default connect(mapStateToProps, mapDispatchToProps)(MyComponent);
The component can be declared by passing the single parameter:
<MyComponent value={event} />
Using Decorators (#)
If you are using decorators, the code below give an example in the case you want to use decorators for your redux connect.
#connect(
(state, ownProps) => {
return {
Foo: ownProps.Foo,
}
}
)
export default class Bar extends React.Component {
If you now check this.props.Foo you will see the prop that was added from where the Bar component was used.
<Bar Foo={'Baz'} />
In this case this.props.Foo will be the string 'Baz'
Hope this clarifies some things.
Related
I've an application when most of the data are stored in the store but the selected item is provided thought the usage of a React.Context.
React-Redux provide the connect api that accept a mapStateToProps function with state and props as a component.
What I would like, if it didn't break the hooks, is something like:
function mapStateToProps(state){
const selectedItemId = useContext(MySelectedItemContext)
return {
item: state.items[selectedItemId]
}
}
but of course it is not possible since I'm outside of the component and cannot invoke the useContext.
So, I tried to use the old API context:
function mapStateToProps(state, props){
return {
item: state.items[props.id]
}
}
export default connect(mapStateToProps)((props) =>
<MySelectedItemContext.Consumer>
{ selectedItemId => <Component id={selectedItemId} {...props}/> }
</MySelectedItemContext.Consumer>)
but this still not works because the connect returns a new component that has the consumer inside instead of outside and id prop is not defined yet in mapStateToProps.
Any idea?
The best way is to remove mapStateToProps and use useSelector hooks and Redux selectors. But if you need mapStateToProps, then you can wrap your component that must be connected to Redux into another component that will get value from context and will pass it to a component that uses Redux.
// Use this component
export function ContextConsumerComponent() {
const selectedItemId = useContext(SelectedItemIdContext);
return <ReduxConsumerComponent id={selectedItemId} />;
}
function mapStateToProps(state, props) {
return {
item: state.items[props.id]
}
}
const ReduxConsumerComponent = connect(mapStateToProps)((props) => {
// props.item will be here
});
i have below snippet.
AnotherFile.js
import MyAccount from './MyAccount';
<MyAccount name='peace and love' />
MyAccount.js
const MyAccount = (props) => {
// I can access props.isLoggedIn and props.setLogout,
// and I can access props.name too, wow
}
const mapStateToProps = (state) => ({
isLoggedIn: state.isLoggedIn
})
const mapDispatchToProps = dispatch => ({
setLogout: () => dispatch(setLogout())
})
export default connect(mapStateToProps, mapDispatchToProps)(MyAccount)
So I pass some props to the connected components, and the presentational component MyAccount can access these props too.
Previously, if I intend to achieve that, I would add a second argument in mapStateToProps, like below. But now it seems it is unnecessary to pass ownProps? Can someone confirm please?
const mapStateToProps = (state, ownProps) => ({
isLoggedIn: state.isLoggedIn,
...ownProps
})
From the react-redux docs:
ownProps (optional)
[...]
You do not need to include values from ownProps in the object returned from mapStateToProps. connect will automatically merge those different prop sources into a final set of props.
So yes, it is unnecessary to explicitly spread ownProps into the props returned by mapStateToProps.
You usually only need ownProps if your component needs the data from its own props to retrieve data from the store, e.g. using an id prop to select a certain item from a list of items.
Below is the Higher order component. The HOC is connected to redux specifically to get access to one of the action creators: importantReduxAction.
function withExtraStuff (InnerComponent) {
return class Enhancer extends React.Component {
constructor(props){
super(props)
this.importantMethod = this.importantMethod.bind(this)
}
importantMethod(){
//try to call the higher order component's action creator
this.props.importantReduxAction()
}
render(){
return <InnerComponent
{...this.props}
importantMethod={this.importantMethod}
/>
}
}
let mapDispatchToProps = (dispatch)=>{
return bindActionCreators({importantReduxAction}, dispatch)
}
return connect(null, mapDispatchToProps, null, {pure: false})(Enhancer)
}
This is the wrapped component that will use the HOC component. It also connects itself to redux in order to gain access to a different method: otherReduxAction.
class ChildComponent extends React.Component {
constructor(props){
super(props)
this.doImportantThing = this.doImportantThing.bind(this)
}
doImportantThing(){
//try to call the higher order component's method (this is where problems occur)
this.props.importantMethod()
//do something with this components dispatch
this.props.otherReduxAction()
}
render(){
return <div>
{this.doImportantThing()}
</div>
}
}
let EnhancedComponent = withExtraStuff(ChildComponent)
let mapDispatchToProps = (dispatch)=>{
return bindActionCreators({otherReduxAction}, dispatch)
}
export default connect(null, mapDispatchToProps, null, {pure: false})(EnhancedComponent)
The problem occurs that my mapDispatchToProps inside of my HOC is being overwritten by the child, and the action creator: importantReduxAction, is never being passed into my HOC. It receives the error that the:
method is undefined
I have solved this by passing the method into my child component like so:
/* CHILD COMPONENT DEFINITION ABOVE */
let mapDispatchToProps = (dispatch)=>{
return bindActionCreators({otherReduxAction, importantReduxAction}, dispatch)
}
But that solution is not really the way that I want things to work. Is there a way to have my HOC merge in the action creators that it wants to use with those of the wrapped component? Or am I going to have to find a new way around this?
TLDR: HOC Component that uses an action creator wraps child component that also has one. HOC action creator gets kicked to curb and never passed.
It looks like you have an issue with your example.
function withExtraStuff (InnerComponent) {
return class Enhancer extends React.Component {/* ... */}
// ...
return connect(/* ... */)(Enhancer)
}
You're returning twice from your HOC, so your Enhancer is never connected.
Is this just a typo in your example? Or do you have this same issue in your code? Because that would indeed cause the issue you're seeing.
The issue here is that you need to merge your props in the higher order component. The redux connect takes a third parameter which is a function (mergeProps). This function takes three parameters. See example here:
function mergeProps(stateProps, dispatchProps, ownProps) {
return {
...stateProps,
...dispatchProps,
...ownProps,
actions: Object.assign({}, dispatchProps.actions, ownProps.actions)
}
}
In my Wrapped Component I set up my mapDispatchToProps like so:
function mapDispatchToProps(dispatch) {
return {
actions: bindActionCreators({
...myDefinedActionsForMyComponent,
}, dispatch)
}
}
And in my HOC I set up my mapDispatchToProps the same way. The issue you are having can be resolved by implementing mergeProps in your HOC (higher order component). If you simply create the mergeProps function and console log the three parameters you'll see the values and can decide how best to join them. Based on my set up I simply had to do an object assign on the actions. You probably need to do something similar.
The connect would then look something like this in your HOC:
return connect(mapStateToProps, mapDispatchToProps, mergeProps)(Wrapper)
I was reading the documentation for the Redux library and it has this example:
In addition to reading the state, container components can dispatch actions. In a similar fashion, you can define a function called mapDispatchToProps() that receives the dispatch() method and returns callback props that you want to inject into the presentational component.
This actually makes no sense. Why do you need mapDispatchToProps when you already have mapStateToProps?
They also provide this handy code sample:
const mapDispatchToProps = (dispatch) => {
return {
onTodoClick: (id) => {
dispatch(toggleTodo(id))
}
}
}
What is this function and why it is useful?
I feel like none of the answers have crystallized why mapDispatchToProps is useful.
This can really only be answered in the context of the container-component pattern, which I found best understood by first reading:Container Components then Usage with React.
In a nutshell, your components are supposed to be concerned only with displaying stuff. The only place they are supposed to get information from is their props.
Separated from "displaying stuff" (components) is:
how you get the stuff to display,
and how you handle events.
That is what containers are for.
Therefore, a "well designed" component in the pattern look like this:
class FancyAlerter extends Component {
sendAlert = () => {
this.props.sendTheAlert()
}
render() {
<div>
<h1>Today's Fancy Alert is {this.props.fancyInfo}</h1>
<Button onClick={sendAlert}/>
</div>
}
}
See how this component gets the info it displays from props (which came from the redux store via mapStateToProps) and it also gets its action function from its props: sendTheAlert().
That's where mapDispatchToProps comes in: in the corresponding container
// FancyButtonContainer.js
function mapDispatchToProps(dispatch) {
return({
sendTheAlert: () => {dispatch(ALERT_ACTION)}
})
}
function mapStateToProps(state) {
return({fancyInfo: "Fancy this:" + state.currentFunnyString})
}
export const FancyButtonContainer = connect(
mapStateToProps, mapDispatchToProps)(
FancyAlerter
)
I wonder if you can see, now that it's the container 1 that knows about redux and dispatch and store and state and ... stuff.
The component in the pattern, FancyAlerter, which does the rendering doesn't need to know about any of that stuff: it gets its method to call at onClick of the button, via its props.
And ... mapDispatchToProps was the useful means that redux provides to let the container easily pass that function into the wrapped component on its props.
All this looks very like the todo example in docs, and another answer here, but I have tried to cast it in the light of the pattern to emphasize why.
(Note: you can't use mapStateToProps for the same purpose as mapDispatchToProps for the basic reason that you don't have access to dispatch inside mapStateToProp. So you couldn't use mapStateToProps to give the wrapped component a method that uses dispatch.
I don't know why they chose to break it into two mapping functions - it might have been tidier to have mapToProps(state, dispatch, props) IE one function to do both!
1 Note that I deliberately explicitly named the container FancyButtonContainer, to highlight that it is a "thing" - the identity (and hence existence!) of the container as "a thing" is sometimes lost in the shorthand
export default connect(...)
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
syntax that is shown in most examples
It's basically a shorthand. So instead of having to write:
this.props.dispatch(toggleTodo(id));
You would use mapDispatchToProps as shown in your example code, and then elsewhere write:
this.props.onTodoClick(id);
or more likely in this case, you'd have that as the event handler:
<MyComponent onClick={this.props.onTodoClick} />
There's a helpful video by Dan Abramov on this here:
Redux: Generating Containers with connect() from React Redux (VisibleTodoList)
mapStateToProps() is a utility which helps your component get updated state(which is updated by some other components),
mapDispatchToProps() is a utility which will help your component to fire an action event (dispatching action which may cause change of application state)
mapStateToProps, mapDispatchToProps and connect from react-redux library provides a convenient way to access your state and dispatch function of your store. So basically connect is a higher order component, you can also think as a wrapper if this make sense for you. So every time your state is changed mapStateToProps will be called with your new state and subsequently as you props update component will run render function to render your component in browser. mapDispatchToProps also stores key-values on the props of your component, usually they take a form of a function. In such way you can trigger state change from your component onClick, onChange events.
From docs:
const TodoListComponent = ({ todos, onTodoClick }) => (
<ul>
{todos.map(todo =>
<Todo
key={todo.id}
{...todo}
onClick={() => onTodoClick(todo.id)}
/>
)}
</ul>
)
const mapStateToProps = (state) => {
return {
todos: getVisibleTodos(state.todos, state.visibilityFilter)
}
}
const mapDispatchToProps = (dispatch) => {
return {
onTodoClick: (id) => {
dispatch(toggleTodo(id))
}
}
}
function toggleTodo(index) {
return { type: TOGGLE_TODO, index }
}
const TodoList = connect(
mapStateToProps,
mapDispatchToProps
)(TodoList)
Also make sure that you are familiar with React stateless functions and Higher-Order Components
Now suppose there is an action for redux as:
export function addTodo(text) {
return {
type: ADD_TODO,
text
}
}
When you do import it,
import {addTodo} from './actions';
class Greeting extends React.Component {
handleOnClick = () => {
this.props.onTodoClick(); // This prop acts as key to callback prop for mapDispatchToProps
}
render() {
return <button onClick={this.handleOnClick}>Hello Redux</button>;
}
}
const mapDispatchToProps = dispatch => {
return {
onTodoClick: () => { // handles onTodoClick prop's call here
dispatch(addTodo())
}
}
}
export default connect(
null,
mapDispatchToProps
)(Greeting);
As function name says mapDispatchToProps(), map dispatch action to props(our component's props)
So prop onTodoClick is a key to mapDispatchToProps function which delegates furthere to dispatch action addTodo.
Also if you want to trim the code and bypass manual implementation, then you can do this,
import {addTodo} from './actions';
class Greeting extends React.Component {
handleOnClick = () => {
this.props.addTodo();
}
render() {
return <button onClick={this.handleOnClick}>Hello Redux</button>;
}
}
export default connect(
null,
{addTodo}
)(Greeting);
Which exactly means
const mapDispatchToProps = dispatch => {
return {
addTodo: () => {
dispatch(addTodo())
}
}
}
mapStateToProps receives the state and props and allows you to extract props from the state to pass to the component.
mapDispatchToProps receives dispatch and props and is meant for you to bind action creators to dispatch so when you execute the resulting function the action gets dispatched.
I find this only saves you from having to do dispatch(actionCreator()) within your component thus making it a bit easier to read.
React redux: connect: Arguments
I'm new to React and redux. Here in the App.React.js I'm passing onRouteChange as props to Post.js. In Post.js, in the redux connect, I receive the state from store and ownprops. I think ownprops will be hold all the props passed to the component by the parent component. But I'm not receiving the onRouteChange in Post.js. Please help me. What I'm missing?
App.React.js
constructor(props) {
super(props);
this.onNavigatorRef = this.onNavigatorRef.bind(this);
this.onRouteChange = this.onRouteChange.bind(this);
this.renderScene = this.renderScene.bind(this);
}
onRouteChange(route, toggleSideMenu = true) {
this.navigator.jumpTo(routes[route]);
if (toggleSideMenu) {
this.props.toggleSideMenu();
}
}
renderScene(route) {
const { isSideMenuOpen, toggleSideMenu } = this.props;
return (
<View style={[styles.sceneView, route.style]}>
<StatusBar hidden={isSideMenuOpen} />
<Header onRouteChange={this.onRouteChange} />
<route.Page onRouteChange={this.onRouteChange} />
</View>
);
}
Post.js
export default connect(
(state, ownProps) => {
console.log(`ownprops=${JSON.stringify(ownProps)}`); //{}
console.log(`ownprops=${ownProps.onRouteChange}`); //undefined
return {
posts: state.posts.map,
onRouteChange: ownProps.onRouteChange,
...ownProps
};
},
(dispatch, ownProps) => {
console.log(`ownprops=${JSON.stringify(dispatch)}`); //{}
console.log(`ownprops=${JSON.stringify(ownProps)}`); //{}
console.log(`ownprops=${ownProps.onRouteChange}`); //undefined
return {
postsActions,
onRouteChange: ownProps.onRouteChange,
...ownProps
};
})(Posts);
First I would like to say that usually it's not a good practice to connect Child components to Redux. You should only connect the high level components to Redux and pass props to the "dumb" components.
As for your question, according to Redux docs:
[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
This means, you should only add here props that are not coming from parent.
mapStateToProps is used to add aditional props you want from state. The props you receive from parent are intact - unless you override them.
(In your case you are overriding them in the mapStateToProps & mapDispatchToProp, but with the same ownProps received from parent, so it doesn't matter.)
In your example you say you pass the onRouteChange to Posts, but it's not shown, you may be passing it to the route.Page or to some Parent component, but it's not shown here. Wherever you create the posts component, you should add the onRouteChange there.
<Posts onRouteChange={YOUR_FUNCTION_HERE} />
You can see in the docs examples how ownProps should be used