Develop Reference

Making react children NOT to refresh when parents state changes

So here is my problem. I have an root component that contains navigation and Switch with every component in my page. Navigation is sliding in and out from the left and the way I'm doing this, I'm changing the state in root component, passing prop to and deciding whether or not, should I add class to my nav. The problem is that every component in my app is re-rendering on opening/closing nav. Here is my root component:
class App extends Component {
constructor(props) {
super(props);
this.state = {
navOpen: false
}
}
toggleNav = () => {
this.setState({
navOpen: !this.state.navOpen
})
}
closeNav = (e) => {
if (this.state.navOpen) {
this.setState({navOpen: false})
}
}
render() {
return (
<main>
<Header/>
<Hamburger navOpen={this.state.navOpen} toggleNav={this.toggleNav}/>
<Navigation navOpen={this.state.navOpen} toggleNav={this.toggleNav}/>
<section className="container-fluid content" onClick={this.closeNav}>
<Switch>
<Route path="/add-recipe/:groupId?" component={NewRecipe}/>
<Route path="/recipes/:page?/:sortType?/:size?" component={RecipeList}/>
<Route path="/recipe/:id" component={Recipe}/>
<Route path="/sign/" component={SignForm}/>
<Route path="/user/:id" component={User}/>
</Switch>
</section>
</main>
);
}
componentDidMount() {
this.props.userActions.getUser(this.props.url);
}
}
function mapStateToProps(state) {
return {url: state.url.url, user: state.user.loggedUser}
}
function mapDispatchToProps(dispatch) {
return {
userActions: bindActionCreators(userActions, dispatch)
}
}
export default withRouter(connect(mapStateToProps, mapDispatchToProps)(App));
Navigation is the only component ( besides hamburger) that cares about his parents state so I have no idea why everything is re-rendering. Does anyone have some ideas?
EDIT:
I've added sCU to my nested components like that:
shouldComponentUpdate(nextProps, nextState) {
// console.log(this.props)
// console.log("next")
// console.log(nextProps)
if (this.props == nextProps) {
return false
}
return true
}
But it didn't change anything. When I open the navigation props for routes remain the same but they still rerender. I tried to move "navOpen" state to navigation and open it from root component via "ref" but every time I call its method I get "Cannot read property 'toggleNav' of null"

You can prevent re-rendering by implementing shouldComponentUpdate on the affected component. Beware though, that rendering does not mean that the DOM is being changed. Rendering in react means that react creates a new copy of its internal node tree and compares it to the DOM to see if and where it needs to update it. So don't worry about re-renders unless your component is expensive to create (i.e. it performs a request to a backend or is heavily animated)

How to pass a wrapped component into React Router without it constantly remounting

We're in the process of upgrading our React App, and after many of hours of pain have realised that passing wrapped components into React Router (V4 and maybe others) causes the component to "remount" every time a new prop is passed in.
Here's the wrapped component...
export default function preload(WrappedComponent, props) {
class Preload extends React.Component {
componentWillMount() {
getDataForComponent(props);
}
render() {
return <WrappedComponent {...props} />;
}
}
return Preload;
}
And here's how we're using it...
const FlagsApp = (props) => {
return (
<Route path="/report/:reportId/flag/:id/edit" component{preload(FlagForm, props)} />
);
};
Anytime we're dispatching an action and then receiving a update, the component remounts, causing lots of problems. According to this thread on github, components will remount if:
you call withRouter(..) during rendering which would create a new component class each time
you pass a new function to Route.component each render, e.g. using anonymous function
{...}} />, which would create a new component as well
If I pass the FlagForm component in directly the problem is fixed, but then I can't take advantage of the preload function.
So, how can I achieve the same outcome, but without the component remounting?
Thanks in advance for any help!

The reason Route is mounting a new component on every update is that it's been assigned a new class each time via preload.
Indeed, each call to preload always returns a distinct anonymous class, even
when called with the same arguments:
console.log( preload(FlagForm,props) != preload(FlagForm,props) ) // true
So, since the issue is that preload being called within the FlagsApp component's render method, start by moving it outside of that scope:
const PreloadedFlagForm = preload(FlagForm, props) //moved out
const FlagsApp = (props) => {
return (
<Route path="/report/:reportId/flag/:id/edit"
component={PreloadedFlagForm} /> //assign component directly
);
};
This way the component for Route won't change between updates.
Now about that lingering props argument for preload: this is actually an anti-pattern. The proper way to pass in props just the standard way you would for any component:
const PreloadedFlagForm = preload(FlagForm) //drop the props arg
const FlagsApp = (props) => {
return (
<Route path="/report/:reportId/flag/:id/edit"
component={<PreloadedFlagForm {...props} />} //spread it in here instead
/>
);
};
And so the code for preload becomes:
export default function preload(WrappedComponent) {
class Preload extends React.Component {
componentWillMount() {
getDataForComponent(this.props);
}
render() {
return <WrappedComponent {...this.props} />;
}
}
return Preload;
}
Hope that helps!

If like me you didn't read the instructions, the answer lies in the render prop of the <Route> component
https://reacttraining.com/react-router/web/api/Route/render-func
render: func
This allows for convenient inline rendering and wrapping without the undesired remounting explained above.
So, instead of passing the wrapper function into the component prop, you must use the render prop. However, you can't pass in a wrapped component like I did above. I still don't completely understand what's going on, but to ensure params are passed down correctly, this was my solution.
My Preload wrapper function is now a React component that renders a Route...
export default class PreloadRoute extends React.Component {
static propTypes = {
preload: PropTypes.func.isRequired,
data: PropTypes.shape().isRequired,
location: PropTypes.shape({
pathname: PropTypes.string.isRequired,
}),
}
componentWillMount() {
this.props.preload(this.props.data);
}
componentWillReceiveProps({ location = {}, preload, data }) {
const { location: prevLocation = {} } = this.props;
if (prevLocation.pathname !== location.pathname) {
preload(data);
}
}
render() {
return (
<Route {...this.props} />
);
}
}
And then I use it like so...
const FlagsApp = (props) => {
return (
<Switch>
<PreloadRoute exact path="/report/:reportId/flag/new" preload={showNewFlagForm} data={props} render={() => <FlagForm />} />
<PreloadRoute exact path="/report/:reportId/flag/:id" preload={showFlag} data={props} render={() => <ViewFlag />} />
<PreloadRoute path="/report/:reportId/flag/:id/edit" preload={showEditFlagForm} data={props} render={() => <FlagForm />} />
</Switch>
);
};
The reason I'm calling this.props.preload both in componentWillMount and componentWillReceiveProps is because I then had the opposite issue of the PreloadRoute component not remounting when navigating, so this solves that.
Hopefully this save lots of people lots of time, as I've literally spent days getting this working just right. That's the cost of being bleeding edge I guess!

React Router redirect hash link

I have created a custom button component for my website's navbar. When the user clicks on a button, the component returns a Redirect, which takes the user to the page they selected.
export default class Button extends Component {
constructor(props){
super(props);
this.state = {redirect:false};
this._handleClick = this._handleClick.bind(this);
}
_handleClick(e) {
e.stopPropagation();
this.setState({redirect: true});
}
componentDidUpdate() {
if (this.state.redirect){
this.setState({redirect:false});
this.props.onRedirect();
}
}
render() {
if (this.state.redirect){
return <Redirect push to={this.props.dest}/>;
}
else {
return (
<li className="button" onClick={this._handleClick}>
<h5>{this.props.text}</h5>
</li>
);
}
}
}
Now, I'd like to add buttons that correspond to different sections of the same page. The simplest way I know of is to use hash links. One example of an address the button would redirect to is:
/home#description
However, React Router does not support doing this out of the box. I looked through a number of packages which add this functionality, such as react-router-hash-link and react-scrollchor. None of these however work with redirects, instead relying on Link or on custom components.
How do I go about adding this functionality to the buttons?

you could update window.location.href since it won't trigger a page refresh.
e.g.
window.location.href = '#your-anchor-tag';

One solution that I can think of is to use HOCs and hooks. The end result:
You'll get your app to scroll to the specified location...
without really needing to create custom buttons/links and...
without making much changes to your existing screens (Eg: HomeScreen)
Bonus: Users can copy, share & use URLs that will automatically scroll to the intended section
With assumption that the code below are pseudocode (they are based on my knowledge and not tested) and assuming there's a HomeScreen component, I would attempt adding <Route/>s to the <Switch/> inside the <Router/>.
<Switch>
<Route to='/home/:section' component={HomeScreen} />
<Route to='/home' component={HomeScreen} />
</Switch>
Then:
function withScrollToTarget(WrappedComponent) {
class WithScroll extends React.Component {
componentDidMount() {
const { match: { params: { section } } } = this.props
// Remember we had 2 <Route/>s, so if `section` is provided...
if (section) {
const scrollToTarget = document.getElementById(section)
// And just in case the item was removed or there was an ID mismatch
if (scrollToTarget) { scrollToTarget.scrollIntoView() }
}
}
render() { return <WrappedComponent {...this.props} /> }
}
return WithScroll
}
function useScrollToTarget(section) {
useEffect(() => {
if (section) {
const scrollToTarget = document.getElementById(section)
if (scrollToTarget) { scrollToTarget.scrollIntoView() }
}
}, [section])
}
Usage:
<nav>
<Link to='/home'>{'Home'}</Link>
<Link to='/home/description'>{'Description'}</Link>
</nav>
class HomeScreen extends React.Component { /* ... */ }
export default withScrollToTarget(HomeScreen)
// or
function HomeScreen() {
const { params: { section } } = useMatch() // from react-router-dom
useScrollTotarget(section)
return (
<div>
<h1 id='introduction'>Introduction</h1>
<h1 id='description'>Description</h1>
</div>
)
}
TLDR:
The route for '/home/:section' must be on top of '/home'. If the opposite, every time when <Switch/> compares the current URL against to, it will evaluate to true upon reaching '/home' and never reach '/home/:section'
scrollIntoView() is a legit function
If this works for you, you should look up on how to forward refs and hoisting statics in HOCs too

Who said React Router doesn't support this out of the box! You don't need those packages. You can redirect a hash i'll give you an example using the React-Router Route.
<Route
exact
path="/signup"
render={props => {
if (props.location.hash === "#foo")
return <Redirect push to="signup#bar"
return <Signup />
}}
/>
Now your version may not have supported this now that I think about it, but let me know if this helps :)
Happy coding!

React-hash-link should work for your redirect use case.
You can add <HashLinkObserver /> to your component tree and it will listen for hash links and scroll accordingly rather than relying on Link or custom components.

I think you should use the react-router-dom.
yarn add react-router-dom
Now update Custom Button Component like this
import React from 'react';
import { withRouter } from "react-router-dom";
class Button extends Component {
constructor(props){
super(props);
this.state = {redirect:false};
this._handleClick = this._handleClick.bind(this);
}
_handleClick(e) {
e.stopPropagation();
this.setState({redirect: true});
}
componentDidUpdate() {
if (this.state.redirect){
this.setState({redirect:false});
//this.props.onRedirect();
this.props.history.push('new uri');
}
}
render() {
if (this.state.redirect){
return <Redirect push to={this.props.dest}/>;
}
else {
return (
<li className="button" onClick={this._handleClick}>
<h5>{this.props.text}</h5>
</li>
);
}
}
}
export default withRouter(Button);

I was trying to solve a similar but slightly different issue, I want to deprecate an old hash route in favor of a new one. The posts here helped me arrive to my eventual solution:
<Route
exact
path={'/thing/:id'}
render={({
match: {
params: { id },
},
}) => (
<Redirect
push
to={`/newThing/${id}`}
/>
)}
/>

I was facing the same issue, I have created HOC to handle hash redirection, you can follow the below steps to achieve a hash redirection
create HOC and add below code to it
fileName : hashComponent
import React, { useEffect } from 'react';
export default function hashComponent(WrappedComponent) {
return function () {
const { pathname, hash }=window.location;
useEffect(() => {
if(hash)
window.location.href=`${pathname}${hash}`;
}, [hash])
return <WrappedComponent />
}
}
import your HOC in the component to which you want to handle hash URL
Then add below line of code while exporting your component
export default hashComponent(YourComponentName)

Best practices for using React refs to call child function

I'm hoping for some clarity on the use of React refs for calling a child function. I have a Parent component that's a toolbar with a few buttons on it, and in the child component I have access to a library's export functionality. I'd like to call this export function on a button click in the parent component. Currently I'm using React refs to accomplish this:
Parent.js [ref]
class Parent extends React.Component {
onExportClick = () => {
this.childRef.export();
}
render() {
return (
<div>
<button onClick={this.onExportClick} />Export</button>
<Child ref={(node) => this.childRef = node;} />
</div>
)
}
}
Child.js [ref]
class Child extends React.Component {
export() {
this.api.exportData();
}
render() {
<ExternalLibComponent
api={(api) => this.api = api}
/>
}
}
This solution works fine, but I've seen a lot of disagreement on if this is the best practice. React's official doc on refs says that we should "avoid using refs for anything that can be done declaratively". In a discussion post for a similar question, Ben Alpert of the React Team says that "refs are designed for exactly this use case" but usually you should try to do it declaratively by passing a prop down.
Here's how I would do this declaratively without ref:
Parent.js [declarative]
class Parent extends React.Component {
onExportClick = () => {
// Set to trigger props change in child
this.setState({
shouldExport: true,
});
// Toggle back to false to ensure child doesn't keep
// calling export on subsequent props changes
// ?? this doesn't seem right
this.setState({
shouldExport: false,
});
}
render() {
return (
<div>
<button onClick={this.onExportClick} />Export</button>
<Child shouldExport={this.state.shouldExport}/>
</div>
)
}
}
Child.js [declarative]
class Child extends React.Component {
componentWillReceiveProps(nextProps) {
if (nextProps.shouldExport) {
this.export();
}
}
export() {
this.api.exportData();
}
render() {
<ExternalLibComponent
api={(api) => this.api = api}
/>
}
}
Although refs are seen as an "escape hatch" for this problem, this declarative solution seems a little hacky, and not any better than using refs. Should I continue to use refs to solve this problem? Or should I go with the somewhat hacky declarative approach?

You don't need to set the shouldExport back to false, you could instead detect the change:
componentWillReceiveProps(nextProps) {
if (nextProps.shouldExport !== this.props.shouldExport) {
this.export();
}
}
Then every toggle of the shouldExport would cause exactly one export. This however looks weird, I'd use a number that I'd increment:
componentWillReceiveProps(nextProps) {
if (nextProps.exportCount > this.props.exportCount) {
this.export();
}
}

I ran into the same problem in many occasions now, and since the React team doesn't encourage it i'll be using the props method for later development, but the problem is sometimes you want to return a value to the parent component, sometimes you need to check the child's state to decide whether to trigger an event or not, therefore refs method will always be my last haven, i suggest you do the same

Communicating between React components

I'm new to react so this is something I don't know. In the app that I
'm working with it has a main component where other components are loaded.
Like this,
render() {
return (
<div className="index">
<HeaderComponent />
<MainHeroComponent />
<AboutComponent />
</div>
);
}
And I want when someone clicks a link in HeaderComponent to show the about component. And hide the MainHeroComponent. How can I do such communication between components in React? Is it possibe?
Thanks

Use React-Router and create routes for this scenario instead of direct communication between components. Sample app structure using react-router
const App = React.createClass({
render() {
return (
<div>
<h1>App</h1>
<HeaderComponent />
</div>
)
}
})
render((
<Router>
<Route path="/" component={App}>
<Route path="hero" component={MainHeroComponent} />
<Route path="about" component={AboutComponent} />
</Route>
</Router>
), document.body)
For more details on router refer: https://github.com/reactjs/react-router/blob/master/docs/guides/RouteConfiguration.md

Aditya's answer is probably a better solution, but if you really want to it your way, you can use state and callbacks.
class Index extends React.Component {
constructor(props) {
super(props);
this.state = {
showHero: true
};
this.toggleShowHero = this.toggleShowHero.bind(this);
}
toggleShowHero() {
this.setState({
showHero: !this.state.showHero
});
}
render() {
return (
<div className="index">
<HeaderComponent onClick={toggleShowHero}/>
{
this.state.showHero ?
<MainHeroComponent /> :
<AboutComponent />
}
</div>
);
}

There are various ways you can achieve this, including React-routers and Redux, but since you're new to React, it'll be good if you get familiar with the basics first. For a start, you have to change the state of the main component to decide which child component to render.
In the main component code snippet you posted, initialize a state in the constructor as follows:
/* in the main component */
constructor(props) {
super(props);
this.state = {
showAbout: true
};
}
Then modify the render function as follows, to pass a reference to your main component, down to your header component:
/* in the main component */
<HeaderComponent mainComponent={this}/>
Then, in HeaderComponent, attach a click event handler to the link on which you want to perform the operation.
/* in HeaderComponent */
<a href="#" ....... onClick={this.showAbout.bind(this)}>Show About</a>
In the same component, define the showAbout function as follows:
/* in HeaderComponent */
showAbout () {
let mainComponent = this.props.mainComponent;
mainComponent.setState({
showAbout: true
)};
}
Finally, back in the render function of the main component:
/* in the main component */
render () {
let mainHeroComponent, aboutComponent;
if (this.state.showAbout) {
aboutComponent = (
<AboutComponent/>
);
} else {
mainHeroComponent = (
<MainHeroComponent/>
);
}
return (
<div className="index">
<HeaderComponent mainComponent={this}/>
{mainHeroComponent}
{aboutComponent}
</div>
);
}
And you're done! Basically, a component gets re-rendered every time its state is changed. So each time you click on the link, the main component's state is changed with a new value of showAbout. This will cause the main component to re-render itself, and, based on the value of showAbout, it will decide whether to render MainHeroComponent or AboutComponent.
But you should make sure you have a similar logic to display MainHeroComponent as well, instead of AboutComponent, just to switch the views.