I created a topbar menu thats needs access to a react component. Inside the topbar file I do not render the other components, but would like to access a function inside one of the components I use.
The project structure looks like this:
Header Component
TopBar Component
LayoutWrapper Component <-- Here I render other components
CustomerDetails Component <-- Here sits the functon I want to call.
This is the TopBar File:
class AdminTopbar extends Component {
renderTopMenu() {
...
if (currentPage.projects || currentPage.customers || currentPage.activities) {
return(
<nav>
...
<li>
// Function needs to be called here
{menuPageType == null ? null : <button onClick={updateActivityCardDetails.bind(this)}>Archiveren</button>}
</li>
</nav>
);
}`enter code here`
}
render() {
return (
<div className="topbar clear">
...
</div>
);
}
}
export default withRouter(AdminTopbar);
ActivityCardDetails file where the function sits:
class ActivityCardDetails extends Component {
constructor(props){
super(props);
// set page title
document.title = 'Strippenkaarten overzicht';
}
updateActivityCardDetails() {
}
}
I found some posts about refs to the parent but I don't have a nested structure between those files.
As a recap: On the TopBar components, which is a separate components without any relations, I would like to call the updateActivityCard method that sits in the ActvityCardDetails components.
React has recently(ish added the context API ) https://reactjs.org/docs/context.html
You'd probably be best off breaking the function out of the component because it's used by different components who aren't strictly hierarchically related. Then just use context to access it from each component.
You can try to wrap your whole structure with a wrapper component and follow the instruction given on each line below:
Wrapper Component <-- Here place a state and a custom function that can set a callbackFunction to its state e.g. myFunc = (callback) => this.setState({updateFunction: callback})
Header Component
TopBar Component <-- Pass the Wrapper Component's state here through props, like state={this.state}
LayoutWrapper Component <-- Pass the Wrapper Component's custom function here through props
CustomerDetails Component <-- Pass the Wrapper Component's custom function here through its parent's props, and call it like 'this.props.myFunc(this.yourInnerUpdateFunction)' on DidMount
Once you're done with this, you should be able to call the updateFunction() from your TopBar component through 'this.props.state.updateFunction()'
P.S. It's not an ideal approach, but it can get the job done if your app isn't too heavy. Hope this helps.
Related
I want to pass a simple string, number or boolean up more than one level in my component tree. From what I read I need to do this with callback functions but I can't seem to get the logic right.
Here is a sample of where I pass a prop down from Parent App to grandchild Breadcrumb. I would like this prop to actually come from the last child in the tree, the "ResultsPage" component.
I realise there are better ways of doing sth like this (redux, context, different structure, etc), the point here for me is learning and to understand how to use callback functions and how to pass a prop up several more than 1 level.
Newbie friendly please - thanks for any input :)
class App extends React.Component {
render() {
return (
<>
<h1>Top level app</h1>
{/* I import the header and pass down prop */}
<Header currentLocation="Results Page" />
{/* I import the main app content */}
<ResultsPage />
</>
);
}
}
function Header(props) {
return (
<>
<h2>
This is the header element. It will have some nav items and the
breadcrumb I import
</h2>
{/* I import the breadcrumb accept the props from parent and pass the props down to child */}
<Crumbs currentLocation={props.currentLocation} />
</>
);
}
function Crumbs(props) {
return (
<>
{/* I display the props I passed down through the tree */}
<h3>
<small>This is the breadcrumb, you are on</small>{" "}
{props.currentLocation}
</h3>
</>
);
}
function ResultsPage() {
return (
<>
<p>
This is the actual results content. I would like this component to tell
the header component that I have loaded so it can update the breadcrumb
to let it know which page is currently loaded in the app.
</p>
</>
);
}
export default App;
To complete this issue I lewave the following solutions:
Codesandbox: Solution to the initial question
Codesandbox: Additional solution for the same problem using only functional components
Hope it helps the next guy :)
Maintain a local state variable to store the location, and pass a callback function through the props to set it.
class App extends React.Component {
constructor(props){
super(props);
this.state = {
currentLocation : "InitialLocation"
}
}
changeCurrentLocation = (newLocation) => {
this.setState({currentLocation : newLocation})
}
render() {
...
<ResultsPage callback={this.changeCurrentLocation}/>
}
}
The changeCurrentLocation function takes the new location as argument and modifies the state. Everytime the state changes, the render function is called again. This would refresh the view with updated state information, in your case - currentLocation.
function ResultsPage({ callback }) {
useEffect(() => {
callback('My Results');
}, [callback])
return (
...
);
}
Best way is to do this as I think keep the state inside a redux store. You can create a listener using subscribe() method in the redux to listen any dispatches from the child components from the parent component.
Also there is some easy method, You can use localstorage. You can store value from the child component and listen it by the parent component using window.addEventListener('storage', function(e) { } callback method. I hope you can understand what I tried to say.
My question is just same as the title.
Let's say I wrote the following code.
class TODOList extends Component {
render() {
const {todos, onClick} = this.props;
return (
<ul>
{todos.map(todo =>
<Todo
key={todo.id}
onClick={onClick}
{...todo}
/>
)}
</ul>
);
}
}
const mapStateToProps = (state) => {
return {
todos: state.todos
}
}
const mapDispatchToProps = (dispatch) => {
return {
onClick(data){
dispatch(complete(data))
}
}
}
export default connect(mapStateToProps,mapDispatchToProps)(TODOList);
Now, after the last line, this code will export the TODOList component with the state as props. It's not that it contains state, but just received state and will have them as 'props', just like the method name 'mapStateToProps' explains.
In the medium post(https://medium.com/#dan_abramov/smart-and-dumb-components-7ca2f9a7c7d0) written by Dan Abramov, container component handles data as state, and presentational property do as props. Isn't it a presentational component that deals with data as props? I'm stuck with the idea that the right container should be one like below.
class CommentList extends React.Component {
this.state = { comments: [] };
componentDidMount() {
fetchSomeComments(comments =>
this.setState({ comments: comments }));
}
render() {
return (
<ul>
{this.state.comments.map(c => (
<li>{c.body}—{c.author}</li>
))}
</ul>
);
}
}
I'm not sure why react-redux named the API 'mapStateToProps', when I tried to make 'stateful'(not handling data by property) container component
First of all these guidelines are not part of the bible
you should write code that is easy to reason about for YOU and your TEAM.
I think you are missing something, A redux Container is different than a react Container.
I mean, connect will create the container for you, it doesn't mean the wraped component is a Container.
Basically you can export both versions from the same file, the Container (connected version) and the presentation version (the none connected one).
Another thing that usually throw people off, is the name of the function and argument of mapStateToProps.
I prefer the name mapStoreToProps as in
map the redux store to the component's props.
the name state can be confusing when we are in the context of react.
Edit
As a followup to your comment:
I totally didn't know these two are actually different. Could you please tell me about more details
They are different in the way that connect is creating a "Container" for you.
connect is a High Order Component that creates the Container Component for us with all the subscription logic + functions to pass portions of the store and action-creators to its children as props (mapStateToProps & mapDispatchToProps).
A "normal" Container is usually refers to a component that you write by hand, its often doesn't deal with how things should look but instead deal with certain logic of the app.
As for the other comments like
The connect HoC of react-redux just injects the properties you can request into your component. It returns a new component that is wrapped around your component so that it can update your component whenever the state you're interested in the redux store is modified
As i mentioned above, this is partially true. It's not just injecting the properties into our component, its subscribing to the store, grabbing it from the Provider (via context) and its doing all these with optimizations in mind, so we won't have to do it by ourselves.
I'm not sure how mapStateToProps can confuse someone. We are talking about a state management library
I've seen some devs that misunderstood this because react has a state and redux has a store (at least that's how it was called in most of the tutorials and documentations).
this can be confusing to some people that are new to either react or redux.
Edit 2
It was a bit confusing due to the sentence 'it doesn't mean the wraped component is a Container.' Why is the wrapped component not a container? Isn't a component created by connect also a container?
I mean that the wrapped component that you wrote doesn't have to be a Container.
You can connect a "Presentation" component:
const Link = ({ active, children, onClick }) => {
if (active) {
return <span>{children}</span>
}
return (
<a
href=""
onClick={e => {
e.preventDefault()
onClick()
}}
>
{children}
</a>
)
}
// ...
export default connect(mapState, mapDispatch)(Link)
mapStateToProps will be called when store data changes. It will pass the returned object as new props for the component. This will not affect the component's state. If you'd like to set a new state after the component got its new props you need to use another lifecycle method: static getDerivedStateFromProps (in earlier versions of react componentWillRecieveProps). The object returned by static getDerivedStateFromProps will be your new state.
https://reactjs.org/docs/state-and-lifecycle.html#adding-lifecycle-methods-to-a-class
connect() will connect your component to the redux store. Withouth the connect function (of course) your mapStateToProps will not work.
I'm not sure why react-redux named the API 'mapStateToProps'
We are talking about the store's state :)
The high level purpose is to seamlessly integrate Redux's state management into the React application. Redux revolves around the store where all the state exists. There is no way to directly modify the store except through reducers whom receive actions from action creators and for that to happen we need for an action to be dispatched from the action creator.
The connect() function directly connects our components to the Redux store by taking the state in the Redux store and mapping it into a prop.
This is power of Redux and its why we use it.
Lets say you are building a component called LaundryList and you want it to render a laundry list. After you have wired up the Provider in your "parent" component, I put it in quotes because technically Provider is a component so it becomes the parent.
You can then import the connect() function from react-redux, pass it mapStateToProps in order to get that laundry list from the Redux store into your LaundryList component.
Now that you have your list of linens inside of the LaundryList component you can start to focus on building a list of elements out of them like so:
class LaundryList extends Component {
render() {
console.log(this.props.linens);
return <div>LaundryList</div>;
}
}
That contains the list of linens object and for every list of linens inside of there we are going to return some jsx that is going to represent that linen on my list.
Back inside my laundry list component I will add a helper method inside the laundry list component called render list like so:
class LaundryList extends Component {
renderList() {
}
render() {
return <div>LaundryList</div>;
}
}
So this purpose of this helper method is to take the list of linens, map over them and return a big blob of jsx like so:
class LaundryList extends Component {
renderList() {
return this.props.linens.map((linen) => {
return (
);
});
}
render() {
return <div>LaundryList</div>;
}
}
I have a react app that ties into localStorage of the browser. On the startup of the app, the localStorage is populated with all the data that is needed to run the app. This data is pulled with AJAX from XML files and constructed to form a localStorageObject that the web app can use as its "database" of information to pull content from...
At the moment, The main component's state is set to the localstorage. So essentially I have the following:
constructor(props) {
super(props);
this.state = {
courseData : JSON.parse(localStorage.getItem("storageID"));,
}
}
The state contains an object that is the entirety of the localStorage. Now I have many children components, who also have children components themselves. Some are components that just need to render once, while others are going to need to rerender with interaction from the user.
After reading, it seems there are many ways to implement a solution. I could have all the components have state, but that's not needed. I could just have the main component have state, and no other component have state. And whenever the state of the main component changes, the props will be based down and reupdated.
Is there a specific method that is best?
This method works, but.
First of all, localStorage calls should be on a componentDidMount function. Otherwise, it wouldn't work on a server-side-rendering case.
Secondly, I'd implement all the initial data fetching on a parent function and then pass down data to the root of react tree:
const localStorageData = localStorage.getItem('some_data')
ReactDom.render(
document.getElementById('my-element'),
<MyComponent
localStorageData={localStorageData}
/>
)
if have many children components it will be difficult to manage state because of deep nesting.
I would recommend using Higher Order Component for your local storage implementation And Pass it down to children. Here How I would do it:
import React from 'react';
var HigherOrderComponent = (Component) =>
class extends React.Component {
state={locStorage:{}}
componentDidMount(){
this.setState({locStorage:window.localStorage.getItem("data")})
}
render() {
return (
<Component
locStorage={this.state.locStorage}
/>
)
}
};
export default HigherOrderComponent;
import HigherOrderComponent from './HigherOrderComponent'
const ChildComponent = ({locStorage}) => {
console.log(locStorage)
return (
<div>
</div>
);
};
export default HigherOrderComponent(ChildComponent);
I have made a parent component and child component (Piechart.js). I passed props from parent component to Piechart component like this ->
<Pie batdata={this.props.BattingRecord}/>
Above code is in parent component. Now I want to extract data from props inside my Piechart component (which is child component).
When I try console.log(this.props) inside my Piechart component constructor function it shows JSON data in console. See screenshot below:
Now I want to get the how parameter inside dismissal see the screenshot above. I think I am not accessing props properly. So what I tried in Piechart component is as follows:
Piechart.jsx:
import React, { Component } from 'react';
const wickets = this.props.batdata.reduce( (a,{dismissal}) =>{ <--Getting error at this line
if(!a[dismissal.how]){
a[dismissal.how]=1;
}else{
a[dismissal.how]=a[dismissal.how] + 1;
}
return a;
}, {});
console.log(wickets);
const dismissals = Object.values(wickets);
const labels = Object.keys(wickets);
//console.log(dismissals);
//console.log(labels);
class Pie extends Component {
constructor(props){
super(props);
console.log(this.props)
}
componentDidMount(){
const piechart = new Chartist.Pie('.ct-pie-chart', data, options, responsiveOptions);
}
render(){
return(
<div>
<div className="col-md-3 col-xs-6 ct-pie-chart">
{this.piechart}
</div>
</div>
)}
}
export default Pie ;
For above code I am getting type error: TypeError: Cannot read property 'batdata' of undefined
The problem is that const wickets is assigned outside of a class which extends Component. You need to move this code inside a member function of class Pie. this.props will only be defined inside of a class which extends Component.
class Pie extends Component {
...
componentDidMount(){
const wickets = this.props.batdata.reduce( (a,{dismissal}) =>{
if(!a[dismissal.how]){
a[dismissal.how]=1;
}else{
a[dismissal.how]=a[dismissal.how] + 1;
}
return a;
}, {});
// Now you can use the value of "wickets" however you wish in this function
this.piechart = new Chartist.Pie('.ct-pie-chart', data, options, responsiveOptions);
}
Even after fixing this problem you are likely to encounter other problems with the pie chart library you are using. If it is intended for use within a React app, you are not rendering it in the correct way.
The problem lies in your Piechart component. The error is quite self-explaining, your this.props is undefined. Without Piechart component's code, the exact problem cannot be told, however, there are couple of common mistakes that can lead to this error:
you are trying to access the props inside an event listener which is not properly bound or
you are trying to access this.props inside a stateless functional component or
inside the component's constructor before super(props) is called.
Edited: You are accessing this.props our side a proper context, you might want to get some idea how this work in JS first: http://javascriptissexy.com/understand-javascripts-this-with-clarity-and-master-it/ .
To correct your component, you can move the reduce function inside your component class, you can put it inside componentDidMount method.
TL;DR Given the following example code:
ReactDOM.render(<MyComponent prop1={someVar} />, someDomNode);
Is it possible to manually pass React context into the instance of MyComponent?
I know this sounds like a weird question given React's nature, but the use case is that I'm mixing React with Semantic UI (SUI) and this specific case is lazy-loading the contents of a SUI tooltip (the contents of the tooltip is a React component using the same code pattern as above) when the tooltip first displays. So it's not a React component being implicitly created by another React component, which seems to break context chain.
I'm wondering if I can manually keep the context chain going rather than having components that need to look for certain data in context AND props.
React version: 0.14.8
No. Before react 0.14 there was method React.withContext, but it was removed.
However you can do it by creating HoC component with context, it would be something like:
import React from 'react';
function createContextProvider(context){
class ContextProvider extends React.Component {
getChildContext() {
return context;
}
render() {
return this.props.children;
}
}
ContextProvider.childContextTypes = {};
Object.keys(context).forEach(key => {
ContextProvider.childContextTypes[key] = React.PropTypes.any.isRequired;
});
return ContextProvider;
}
And use it as following:
const ContextProvider = createContextProvider(context);
ReactDOM.render(
<ContextProvider>
<MyComponent prop1={someVar} />
</ContextProvider>,
someDomNode
);
In React 15 and earlier you can use ReactDOM.unstable_renderSubtreeIntoContainer instead of ReactDOM.render. The first argument is the component who's context you want to propagate (generally this)
In React 16 and later there's the "Portal" API: https://reactjs.org/docs/portals.html