I have a Search parent component and a SideBar child component, I am trying to get context in SideBar, but everytime it returns empty.
I followed the tutorial exactly like: https://itnext.io/manage-react-state-without-redux-a1d03403d360
but it never worked, anyone know what I did wrong?
Here is the codesandbox link to the project: https://codesandbox.io/s/vigilant-elion-3li7v
I wrote that article.
To solve your specific problem:
When using the HOC withStore you're injecting the prop store into the wrapped component: <WrappedComponent store={context}.
The value of the prop store is an object that contains 3 functions: get, set, and remove.
So, instead of printing it, you should use it. For example this.props.store.get("currentAlbums") or this.props.store.set("currentAlbums", [album1, album2]).
This example is forked by your code: https://codesandbox.io/s/nameless-wood-ycps6
However
Don't rewrite the article code, but use the library: https://www.npmjs.com/package/#spyna/react-store which is already packed, tested, and has more features.
An event better solution is to use this library: https://www.npmjs.com/package/react-context-hook. That is the new version of the one in that article.
This is an example of a sidebar that updates another component content: https://codesandbox.io/s/react-context-hook-sidebar-xxwkm
Be careful when using react context API
Using the React Context API to manage the global state of an application has some performance issues, because each time the context changes, every child component is updated.
So, I don't recommend using it for large projects.
The library https://www.npmjs.com/package/#spyna/react-store has this issue.
The library https://www.npmjs.com/package/react-context-hook does not.
You pass the store as a prop, so to access it, you need this.props.store in your SideBar.
Not this.state.store
Create a wrapping App component around Search and Sidebar:
const App = props => (
<div>
<Search />
<SideBar />
</div>
);
export default createStore(App);
Now you can manipulate state with set and get that you have available in child components Search and Sidebar.
In Search component you can have something like:
componentDidMount() {
this.props.store.set("showModal", this.state.showModal);
}
also wrapped with withStore(Search) ofc.
and in SideBar you can now call:
render() {
return (
<div>
{"Sidebar: this.state.store: ---> " +
JSON.stringify(this.props.store.get("showModal"))}
}
</div>
);
}
and you will get the output.
I'm coming from the angular world where I could extract logic to a service/factory and consume them in my controllers.
I'm trying to understand how can I achieve the same in a React application.
Let's say that I have a component that validates user's password input (it's strength). It's logic is pretty complex hence I don't want to write it in the component it self.
Where should I write this logic? In a store if I'm using flux? Or is there a better option?
The issue becomes extremely simple when you realize that an Angular service is just an object which delivers a set of context-independent methods. It's just the Angular DI mechanism which makes it look more complicated. The DI is useful as it takes care of creating and maintaining instances for you but you don't really need it.
Consider a popular AJAX library named axios (which you've probably heard of):
import axios from "axios";
axios.post(...);
Doesn't it behave as a service? It provides a set of methods responsible for some specific logic and is independent from the main code.
Your example case was about creating an isolated set of methods for validating your inputs (e.g. checking the password strength). Some suggested to put these methods inside the components which for me is clearly an anti-pattern. What if the validation involves making and processing XHR backend calls or doing complex calculations? Would you mix this logic with mouse click handlers and other UI specific stuff? Nonsense. The same with the container/HOC approach. Wrapping your component just for adding a method which will check whether the value has a digit in it? Come on.
I would just create a new file named say 'ValidationService.js' and organize it as follows:
const ValidationService = {
firstValidationMethod: function(value) {
//inspect the value
},
secondValidationMethod: function(value) {
//inspect the value
}
};
export default ValidationService;
Then in your component:
import ValidationService from "./services/ValidationService.js";
...
//inside the component
yourInputChangeHandler(event) {
if(!ValidationService.firstValidationMethod(event.target.value) {
//show a validation warning
return false;
}
//proceed
}
Use this service from anywhere you want. If the validation rules change you need to focus on the ValidationService.js file only.
You may need a more complicated service which depends on other services. In this case your service file may return a class constructor instead of a static object so you can create an instance of the object by yourself in the component. You may also consider implementing a simple singleton for making sure that there is always only one instance of the service object in use across the entire application.
The first answer doesn't reflect the current Container vs Presenter paradigm.
If you need to do something, like validate a password, you'd likely have a function that does it. You'd be passing that function to your reusable view as a prop.
Containers
So, the correct way to do it is to write a ValidatorContainer, which will have that function as a property, and wrap the form in it, passing the right props in to the child. When it comes to your view, your validator container wraps your view and the view consumes the containers logic.
Validation could be all done in the container's properties, but it you're using a 3rd party validator, or any simple validation service, you can use the service as a property of the container component and use it in the container's methods. I've done this for restful components and it works very well.
Providers
If there's a bit more configuration necessary, you can use a Provider/Consumer model. A provider is a high level component that wraps somewhere close to and underneath the top application object (the one you mount) and supplies a part of itself, or a property configured in the top layer, to the context API. I then set my container elements to consume the context.
The parent/child context relations don't have to be near each other, just the child has to be descended in some way. Redux stores and the React Router function in this way. I've used it to provide a root restful context for my rest containers (if I don't provide my own).
(note: the context API is marked experimental in the docs, but I don't think it is any more, considering what's using it).
//An example of a Provider component, takes a preconfigured restful.js
//object and makes it available anywhere in the application
export default class RestfulProvider extends React.Component {
constructor(props){
super(props);
if(!("restful" in props)){
throw Error("Restful service must be provided");
}
}
getChildContext(){
return {
api: this.props.restful
};
}
render() {
return this.props.children;
}
}
RestfulProvider.childContextTypes = {
api: React.PropTypes.object
};
Middleware
A further way I haven't tried, but seen used, is to use middleware in conjunction with Redux. You define your service object outside the application, or at least, higher than the redux store. During store creation, you inject the service into the middleware and the middleware handles any actions that affect the service.
In this way, I could inject my restful.js object into the middleware and replace my container methods with independent actions. I'd still need a container component to provide the actions to the form view layer, but connect() and mapDispatchToProps have me covered there.
The new v4 react-router-redux uses this method to impact the state of the history, for example.
//Example middleware from react-router-redux
//History is our service here and actions change it.
import { CALL_HISTORY_METHOD } from './actions'
/**
* This middleware captures CALL_HISTORY_METHOD actions to redirect to the
* provided history object. This will prevent these actions from reaching your
* reducer or any middleware that comes after this one.
*/
export default function routerMiddleware(history) {
return () => next => action => {
if (action.type !== CALL_HISTORY_METHOD) {
return next(action)
}
const { payload: { method, args } } = action
history[method](...args)
}
}
I needed some formatting logic to be shared across multiple components and as an Angular developer also naturally leaned towards a service.
I shared the logic by putting it in a separate file
function format(input) {
//convert input to output
return output;
}
module.exports = {
format: format
};
and then imported it as a module
import formatter from '../services/formatter.service';
//then in component
render() {
return formatter.format(this.props.data);
}
Keep in mind that the purpose of React is to better couple things that logically should be coupled. If you're designing a complicated "validate password" method, where should it be coupled?
Well you're going to need to use it every time the user needs to input a new password. This could be on the registration screen, a "forgot password" screen, an administrator "reset password for another user" screen, etc.
But in any of those cases, it's always going to be tied to some text input field. So that's where it should be coupled.
Make a very small React component that consists solely of an input field and the associated validation logic. Input that component within all of the forms that might want to have a password input.
It's essentially the same outcome as having a service/factory for the logic, but you're coupling it directly to the input. So you now never need to tell that function where to look for it's validation input, as it is permanently tied together.
Same situation: Having done multiple Angular projects and moving to React, not having a simple way to provide services through DI seems like a missing piece (the particulars of the service aside).
Using context and ES7 decorators we can come close:
https://jaysoo.ca/2015/06/09/react-contexts-and-dependency-injection/
Seems these guys have taken it a step further / in a different direction:
http://blog.wolksoftware.com/dependency-injection-in-react-powered-inversifyjs
Still feels like working against the grain. Will revisit this answer in 6 months time after undertaking a major React project.
EDIT: Back 6 months later with some more React experience. Consider the nature of the logic:
Is it tied (only) to UI? Move it into a component (accepted answer).
Is it tied (only) to state management? Move it into a thunk.
Tied to both? Move to separate file, consume in component through a selector and in thunks.
Some also reach for HOCs for reuse but for me the above covers almost all use cases. Also, consider scaling state management using ducks to keep concerns separate and state UI-centric.
I also came from Angular.js area and the services and factories in React.js are more simple.
You can use plain functions or classes, callback style and event Mobx like me :)
// Here we have Service class > dont forget that in JS class is Function
class HttpService {
constructor() {
this.data = "Hello data from HttpService";
this.getData = this.getData.bind(this);
}
getData() {
return this.data;
}
}
// Making Instance of class > it's object now
const http = new HttpService();
// Here is React Class extended By React
class ReactApp extends React.Component {
state = {
data: ""
};
componentDidMount() {
const data = http.getData();
this.setState({
data: data
});
}
render() {
return <div>{this.state.data}</div>;
}
}
ReactDOM.render(<ReactApp />, document.getElementById("root"));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>JS Bin</title>
</head>
<body>
<div id="root"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
</body>
</html>
Here is simple example :
I am from Angular as well and trying out React, as of now, one recommended(?) way seems to be using High-Order Components:
A higher-order component (HOC) is an advanced technique in React for
reusing component logic. HOCs are not part of the React API, per se.
They are a pattern that emerges from React’s compositional nature.
Let's say you have input and textarea and like to apply the same validation logic:
const Input = (props) => (
<input type="text"
style={props.style}
onChange={props.onChange} />
)
const TextArea = (props) => (
<textarea rows="3"
style={props.style}
onChange={props.onChange} >
</textarea>
)
Then write a HOC that does validate and style wrapped component:
function withValidator(WrappedComponent) {
return class extends React.Component {
constructor(props) {
super(props)
this.validateAndStyle = this.validateAndStyle.bind(this)
this.state = {
style: {}
}
}
validateAndStyle(e) {
const value = e.target.value
const valid = value && value.length > 3 // shared logic here
const style = valid ? {} : { border: '2px solid red' }
console.log(value, valid)
this.setState({
style: style
})
}
render() {
return <WrappedComponent
onChange={this.validateAndStyle}
style={this.state.style}
{...this.props} />
}
}
}
Now those HOCs share the same validating behavior:
const InputWithValidator = withValidator(Input)
const TextAreaWithValidator = withValidator(TextArea)
render((
<div>
<InputWithValidator />
<TextAreaWithValidator />
</div>
), document.getElementById('root'));
I created a simple demo.
Edit: Another demo is using props to pass an array of functions so that you can share logic composed by multiple validating functions across HOCs like:
<InputWithValidator validators={[validator1,validator2]} />
<TextAreaWithValidator validators={[validator1,validator2]} />
Edit2: React 16.8+ provides a new feature, Hook, another nice way to share logic.
const Input = (props) => {
const inputValidation = useInputValidation()
return (
<input type="text"
{...inputValidation} />
)
}
function useInputValidation() {
const [value, setValue] = useState('')
const [style, setStyle] = useState({})
function handleChange(e) {
const value = e.target.value
setValue(value)
const valid = value && value.length > 3 // shared logic here
const style = valid ? {} : { border: '2px solid red' }
console.log(value, valid)
setStyle(style)
}
return {
value,
style,
onChange: handleChange
}
}
https://stackblitz.com/edit/react-shared-validation-logic-using-hook?file=index.js
If you are still looking for a service like Angular, you can try the react-rxbuilder library
You can use #Injectable to register the service, and then you can use useService or CountService.ins to use the service in the component
import { RxService, Injectable, useService } from "react-rxbuilder";
#Injectable()
export class CountService {
static ins: CountService;
count = 0;
inc() {
this.count++;
}
}
export default function App() {
const [s] = useService(CountService);
return (
<div className="App">
<h1>{s.count}</h1>
<button onClick={s.inc}>inc</button>
</div>
);
}
// Finally use `RxService` in your root component
render(<RxService>{() => <App />}</RxService>, document.getElementById("root"));
Precautions
Depends on rxjs and typescript
Cannot use arrow functions in the service
Service is not limited to Angular, even in Angular2+,
Service is just collection of helper functions...
And there are many ways to create them and reuse them across the application...
1) They can be all separated function which are exported from a js file, similar as below:
export const firstFunction = () => {
return "firstFunction";
}
export const secondFunction = () => {
return "secondFunction";
}
//etc
2) We can also use factory method like, with collection of functions... with ES6 it can be a class rather than a function constructor:
class myService {
constructor() {
this._data = null;
}
setMyService(data) {
this._data = data;
}
getMyService() {
return this._data;
}
}
In this case you need make an instance with new key...
const myServiceInstance = new myService();
Also in this case, each instance has it's own life, so be careful if you want to share it across, in that case you should export only the instance you want...
3) If your function and utils not gonna be shared, you can even put them in React component, in this case, just as function in your react component...
class Greeting extends React.Component {
getName() {
return "Alireza Dezfoolian";
}
render() {
return <h1>Hello, {this.getName()}</h1>;
}
}
4) Another way you may handle things, could be using Redux, it's a temporary store for you, so if you have it in your React application, it can help you with many getter setter functions you use... It's like a big store that keep tracks of your states and can share it across your components, so can get rid of many pain for getter setter stuffs we use in the services...
It's always good to do a DRY code and not repeating what needs to be used to make the code reusable and readable, but don't try to follow Angular ways in React app, as mentioned in item 4, using Redux can reduce your need of services and you limit using them for some reuseable helper functions like item 1...
I am in the same boat like you. In the case you mention, I would implement the input validation UI component as a React component.
I agree the implementation of the validation logic itself should (must) not be coupled. Therefore I would put it into a separate JS module.
That is, for logic that should not be coupled use a JS module/class in separate file, and use require/import to de-couple the component from the "service".
This allows for dependency injection and unit testing of the two independently.
In the React world we have two types of logic: Stateful and stateless. Now this is the main concept to grasp when starting with React. That here we update state which should update UI as opposed to Angular's direct updates of dom. The two types of logics are:
That do not depend on state changes, i.e. static logic which doesn't need to re-render something based on state changes. For such cases just create regular js files and import them like a library or helper methods
If you have some code that depends on state and u need to resuse it then two options - hocs and the newer hooks. Hooks are a bit hard to wrap our heads around but basically they would force their parent to rerender if their internal state changes so any stateful logic can be defined and reused in different components, and each hook instance would have its own isolated scope.
It's a little bit of a thinking shift to understand state and declarative components but feel free to ask followup questions in comments
or you can inject the class inheritance "http" into React Component
via props object.
update :
ReactDOM.render(<ReactApp data={app} />, document.getElementById('root'));
Simply edit React Component ReactApp like this:
class ReactApp extends React.Component {
state = {
data: ''
}
render(){
return (
<div>
{this.props.data.getData()}
</div>
)
}
}
It is possible to use export keyword to use functions from file which contains necessary methods.
Let me show an example. Let's say we have a file called someService.ts:
export const foo = (formId: string) => {
// ... the code is omitted for the brevity
}
export const bar = (): Entity[] => [
// ... the code is omitted for the brevity
]
export default {
foo,
bar,
}
Then we can use this service in component like this:
import {
foo,
bar,
} from './someService'
const InnerOrderModal: FC = observer(() => {
const handleFormClick = (value: unknown, item: any) => {
foo(item.key)
bar()
return <></>
}
I have a navigation toolbar, with H1 in it.
I also various sub content for each page, as child component.
How can I pass the title information, from the child page component, to the parent navigation?
I've tried to use Context, but it only propagate from Parent to Childs.
Her is a simplified exemple:
const App = React.createClass({
render() {
return (
<div>
<toolbar>
<h1>{myTitleAccordingToPage}</h1>
</toolbar>
<main>
{this.props.children}
</main>
</div>
)
}
})
const A = React.createClass({
render() {
return (
<div>
Content for A page
</div>
)
}
})
const B = React.createClass({
render() {
return (
<div>
Content for B page
</div>
)
}
})
Extract state for your navigation either into a store, or somewhere else, and propagate that state to your application via props.
var page = {
title: 'foo'
otherData: ''
}
ReactDOM.render( <App page={ page }, element )
Now your top-level component knows about the state and can filter accordingly down to its children, for example, you might change your App render function to pass different bits of the application state down to different children i.e.
(I'm passing props explicitly here to show what is going on, and using a pure function to render, use a class and render method if that is more comfortable for you, the advantage of only ever passing props is that it is easier to make your functions pure, which has many advantages)
const App = props => {
<div>
<Toolbar title={ props.page.title } />
<Main otherData={ props.page.otherData />
</div>
}
Now you have created top-down data flow, making your application more predictable and possibly paving the way to use the pure render function to maybe give you performance boosts for free. The key with top-down data-flow is really making your application more predictable, which should translate into testability, and thus reliability, and makes hacking on your application easier.
The react-router module can help with creating structures like this. There is a small learning phase when adopting the module but the benefits for an app like the one you are creating should outweigh this and the speed of development once learnt may very well outweigh any learning outlay you invest into it.
Possible it's time to use Flex https://facebook.github.io/flux/docs/dispatcher.html#content
Usable approuch to two way data binding http://voidcanvas.com/react-tutorial-two-way-data-binding/
Original documentation to two way data binding, but mixin now is now supported https://facebook.github.io/react/docs/two-way-binding-helpers.html
( For mixin possible to use react-mixin npm package )
EDIT:
There is an opinion at comments that: "two-way data-binding is often a bad idea, and if your application makes more sense with two-way data binding then React should probably not be the framework to employ". So you need to rearrange your application architecture to avoid using two-way data binding if possible. Use flux instead.
I have a stateless functional component in React 0.14 that worked in React 0.13, but now returns the following error:
No render method found on the returned component instance: you may
have forgotten to define render, returned null/false from a
stateless component, or tried to render an element whose type is a
function that isn't a React component.
This is my component:
function ToggleDisplay(props) {
//should render a <noscript> per React's implementation
if(props.if === false) {
// return <noscript></noscript>; //do I have to do this manually now?
return null;
}
let style = {};
if(shouldHide(props)) {
style.display = 'none';
}
return (
<span style={style} {...props} />
);
}
Do I have to manually return a <noscript> now? Is there another way to return null in stateless component?
As of React 15.0, you can return null from a stateless functional component. (See #5355). No more having to return <noscript /> 🎉
The change that made this possible is that React removed support for component classes that don’t inherit from React.Component, meaning they can reliably differentiate between React components (classes that inherit React.Component) and functional stateless components. So the PR to enable the functionality just involved removing and simplifying the code that instantiates the components.
Looks like not, this is a technical constraint in Javascript. To support arrow functions and plain functions as "components" React needs to know if we can call new on them.
We can call new on everything if they're plain functions as long as
they return a ReactElement. However, that won't work for
null/false/string return values and we want to support those too. We
also can't call new on arrow functions. Likewise, we can't NOT call
new on classes.
Relevant GitHub Issue
I currently have a doubt about the correct combined implementation of react-router Link navigation and shouldComponentUpdate() on the root application level.
That is, I have a root component called App.jsx which contains a global component with a header, footer, sidebar etc and this same component has an ajax long-poll which retrieves new registrations in the system and updates the state when new users register.
Since I don't want to push a re-render to the component (and therefore all it's children) on ajax responses that don't have updates I decided to make use of the lovely shouldComponentUpdate() method.
So, I came up with something like this - noting that I'm making use of lo-dash:
shouldComponentUpdate (/*prevProps*/, prevState) {
return !_.isEqual(this.state,prevState);
}
With this the component correctly ignores irrelevant responses about the latest registrations.
Now, the problem appears when I have to make the routing. To clarify before, this is the kind of structure of the render():
Note: the _routerTransitionKey is just a helper I have to not make transitions when I'm navigating internal views state and it's working correctly.
<Grid key='app' id="wrapper" className="no-padding">
<Header user={this.state.user} allRegistrations={this.state.allRegistrations}/>
<section id="page-wrapper">
<NotificationArea key='internalNotification' />
<RouteHandler key={_routerTransitionKey} user={this.state.user} allRegistrations={this.state.allRegistrations}/>
</section>
</Grid>
Because I have the RouteHandler inside this global component, I have the issue that a change in the route is completely ignored by it, since the application state itself didn't change. That causes the component to never trigger the render() on navigation and therefore never update the RouteHandler.
What I needed would be something like:
shouldComponentUpdate (/*prevProps*/, prevState) {
return !_.isEqual(this.state,prevState) || ROUTE_CHANGED ;
}
My question is: does anybody out there knows of a clever approach to this issue? I'm trying to avoid having to create yet another wrapping component to handle the Routes before they reach this App component I currently have...
So, after the tip from #WayneC, even though the react-router doesn't inject the props directly into the react component props, there's a possible way inspired by that approach.
I achieved what I wanted by doing a slight change using not the this.props, but instead the this.context.router.getCurrentPath()
So now the solution looks like this:
shouldComponentUpdate (/*nextProps*/, nextState) {
return !_.isEqual(this.state,nextState) || this.context.router.getCurrentPath() !== _routerTransitionKey;
}
Just to make it clearer, my _routerTransitionKey gets its value from an imported Util that looks mostly like this:
var Utils = {
Router: {
TransitionKey: {
get: function(){
return Router.HistoryLocation.getCurrentPath();
}
}
}
}
_routerTransitionKey = Utils.Router.TransitionKey.get();
This _routerTransitionKey is scoped in an upper level, and I modify it on every render(), so that I keep track of it for later comparison.
And... that's it.