Using React + Typescript, I'd like to create a children prop that only accepts a single child that accepts a understands and accepts a ref attribute. Basically, my children type should accept:
an instance of a React class component
a standard React HTML element (e.g. <button>, <div>)
a forwardRef wrapped function component
It should not accept:
a regular function component
a text node, like a string or number
My goal with this children type is to inject a ref into the child using React.cloneElement with some level of certainty that ref will not go completely ignored.
I have tried
import React from "react";
type Props = {
// EDIT: This is how I originally typed `children` to
// get a decent compile time check that returns errors
// if the children is a text node or multiple elements.
// The same effect can be achieved with the `ReactElement` type.
// children: React.FunctionComponentElement<React.RefAttributes<HTMLElement>>;
children: React.ReactElement;
};
const MyComponent = (props: Props) => {
const childRef = React.useRef(null);
const child = React.Children.only(props.children);
if (!React.isValidElement(child)) {
return props.children;
}
return React.cloneElement(child, {ref: childRef});
};
This compiles, and MyComponent not accept text nodes as children, but it does accept non forwardRef function components without complaint.
// This fails with an error that a text node is not a valid child.
<MyComponent>hello</MyComponent>
// This compiles without issue, but should fail because MyText is not a `forwardRef` component.
const MyText = () => <span>hello</span>;
<MyComponent><MyText/></MyComponent>
I've also tried some other types, but this feels like the closest I've gotten.
Is creating a type requirement like this possible with Typescript? If so, how can it be done?
No.
There is no way to enforce that an instance of a React component is utilizing React.forwardRef(). That's because React doesn't preserve the type of the original function or class a component instance was created with. An instance of a React component in JSX will always be JSX.Element, React.FunctionComponentElement<...>, or React.CElement<...>.
Example:
const MyForwardedRefComponent = React.forwardRef<HTMLDivElement>((props, ref) => {
return <div ref={ref}>{props.children}</div>;
});
// JSX.Element
const myInstance = <MyForwardedRefComponent />;
// React.FunctionComponentElement<{}>
const myOtherInstance = React.createElement(MyForwardedRefComponent);
However, you can enforce that a React component only accepts a single child element, and TypeScript will warn you accordingly. This is about as good as you can hope for you in your case.
Example:
const SingleChildOnly: React.FC<{ children: React.ReactElement }> = ({
children,
}) => {
const ref = React.useRef(null);
const child = React.Children.only(children);
return React.cloneElement(child, { ref });
};
const thisIsOkay = (
<SingleChildOnly>
<div>hello</div>
</SingleChildOnly>
);
// error
const thisIsNotOkay = (
<SingleChildOnly>
<div>hello</div>
<div>hello there</div>
</SingleChildOnly>
);
I also couldn't find a typescript solution for this.
What I wanted to do is create a Tooltip component to wrap other components with.
The best I can come up with so far, is writing the SingleChildOnly component as a custom hook which will return: a reference to put on the child, any props to add to the child and the Element you want to render.
This way you can force the child component to be able to accept a ref.
The downside is that you need to write much more code when using the SingleChildOnly component.
I thought of creating TextWithTooltip ButtonWithTooltip base components wrapping only a simple html span or button.
Don't know if it's applicable for your use case
I have tried pass value from parent to grandchild component, and it works. While I am thinking if there is another simpler or other way of passing props in shorter path.
What I did is quite cumbersome in codesandbox
There may be a common problem in react world called prop drilling by passing data to children only using props.
I would recommend only 2-level passing, if you need pass data deeper then you probably doing something wrong.
Use one of popular state management library (if your project is big) or React context (which is awesome)
Create a folder called /contexts and put contexts there. The structure of files can be like shown below:
First you need to create a context itself
type ClientContextState = {
data: User;
set: (data: User) => void;
logout: () => void;
};
// empty object as a default value
export const UserContext = createContext<UserContextState>({} as UserContextState);
Then create a Provider wrapper component
export const UserProvider = ({ children }: Props) => {
const [data, setData] = useState<User>({});
const sharedState = {
data,
set: setData
logout: () => setData(null)
}
return <UserContext.Provider value={sharedState}>{children}</UserContext.Provider>
});
You may also want to have an alias of useContext hook:
export const useUser = () => {
return useContext(UserContext);
};
After all this whenever you wrap your components or app to <UserProvider>...</UserProvider> you can use our hook to access data and methods form sharedState from any place you want:
export LogoutButton = () => {
const {data, logout} = useUser();
return <Button onClick={() => logout()}>Logout from {data.name}</Button>
}
Whenever you want to pass props or data from Grandparent to child component, always use react-redux. This is useful to maintain the state and access the data from anywhere/any component.
Another way is to use useContext hooks which you can use to pass the props
Following are the steps to use useContext hooks
Creating the context
The built-in factory function createContext(default) creates a context instance:
import { createContext } from 'react';
const Context = createContext('Default Value');
The factory function accepts one optional argument: the default value.
Providing the context
Context.Provider component available on the context instance is used to provide the context to its child components, no matter how deep they are.
To set the value of context use the value prop available on the
<Context.Provider value={value} />:
function Main() {
const value = 'My Context Value';
return (
<Context.Provider value={value}>
<MyComponent />
</Context.Provider>
);
}
Again, whatβs important here is that all the components thatβd like later to consume the context have to be wrapped inside the provider component.
If you want to change the context value, simply update the value prop.
Consuming the context: Consuming the context can be performed in 2 ways.
The first way, the one I recommend, is to use the useContext(Context) React hook:
import { useContext } from 'react';
function MyComponent() {
const value = useContext(Context);
return <span>{value}</span>;
}
Generally it's helpful to consider whether moving state down the hierarchy would be the simplest route. That means lifting the component instantiation to a place closer to the state being used. In your example, that could mean Component_data is used inside Component and passed to its children there, removing one step in the nested data flow. Even better, would be that Child.a accesses Component_data.A directly.
In a real app with cases where accessing the data directly is less feasible, a solution I lean towards is using Context to set data in the parent that retrieves it, and then I can access it however deeply nested the component might be that needs it.
i.e. in App I would create the Context provider, and in ChildA I access it via useContext hook.
Further reading
https://reactjs.org/docs/context.html
https://overreacted.io/before-you-memo/#solution-1-move-state-down (this post is about an alternative to using useMemo but has an illustrative example of why moving state down is a good thing)
In this example, I have this react class:
class MyDiv extends React.component
constructor(){
this.state={sampleState:'hello world'}
}
render(){
return <div>{this.state.sampleState}
}
}
The question is if I can add React hooks to this. I understand that React-Hooks is alternative to React Class style. But if I wish to slowly migrate into React hooks, can I add useful hooks into Classes?
High order components are how we have been doing this type of thing until hooks came along. You can write a simple high order component wrapper for your hook.
function withMyHook(Component) {
return function WrappedComponent(props) {
const myHookValue = useMyHook();
return <Component {...props} myHookValue={myHookValue} />;
}
}
While this isn't truly using a hook directly from a class component, this will at least allow you to use the logic of your hook from a class component, without refactoring.
class MyComponent extends React.Component {
render(){
const myHookValue = this.props.myHookValue;
return <div>{myHookValue}</div>;
}
}
export default withMyHook(MyComponent);
Class components don't support hooks -
According to the Hooks-FAQ:
You canβt use Hooks inside of a class component, but you can definitely mix classes and function components with Hooks in a single tree. Whether a component is a class or a function that uses Hooks is an implementation detail of that component. In the longer term, we expect Hooks to be the primary way people write React components.
As other answers already explain, hooks API was designed to provide function components with functionality that currently is available only in class components. Hooks aren't supposed to used in class components.
Class components can be written to make easier a migration to function components.
With a single state:
class MyDiv extends Component {
state = {sampleState: 'hello world'};
render(){
const { state } = this;
const setState = state => this.setState(state);
return <div onClick={() => setState({sampleState: 1})}>{state.sampleState}</div>;
}
}
is converted to
const MyDiv = () => {
const [state, setState] = useState({sampleState: 'hello world'});
return <div onClick={() => setState({sampleState: 1})}>{state.sampleState}</div>;
}
Notice that useState state setter doesn't merge state properties automatically, this should be covered with setState(prevState => ({ ...prevState, foo: 1 }));
With multiple states:
class MyDiv extends Component {
state = {sampleState: 'hello world'};
render(){
const { sampleState } = this.state;
const setSampleState = sampleState => this.setState({ sampleState });
return <div onClick={() => setSampleState(1)}>{sampleState}</div>;
}
}
is converted to
const MyDiv = () => {
const [sampleState, setSampleState] = useState('hello world');
return <div onClick={() => setSampleState(1)}>{sampleState}</div>;
}
Complementing Joel Cox's good answer
Render Props also enable the usage of Hooks inside class components, if more flexibility is needed:
class MyDiv extends React.Component {
render() {
return (
<HookWrapper
// pass state/props from inside of MyDiv to Hook
someProp={42}
// process Hook return value
render={hookValue => <div>Hello World! {hookValue}</div>}
/>
);
}
}
function HookWrapper({ someProp, render }) {
const hookValue = useCustomHook(someProp);
return render(hookValue);
}
For side effect Hooks without return value:
function HookWrapper({ someProp }) {
useCustomHook(someProp);
return null;
}
// ... usage
<HookWrapper someProp={42} />
Source: React Training
you can achieve this by generic High order components
HOC
import React from 'react';
const withHook = (Component, useHook, hookName = 'hookvalue') => {
return function WrappedComponent(props) {
const hookValue = useHook();
return <Component {...props} {...{[hookName]: hookValue}} />;
};
};
export default withHook;
Usage
class MyComponent extends React.Component {
render(){
const myUseHookValue = this.props.myUseHookValue;
return <div>{myUseHookValue}</div>;
}
}
export default withHook(MyComponent, useHook, 'myUseHookValue');
Hooks are not meant to be used for classes but rather functions. If you wish to use hooks, you can start by writing new code as functional components with hooks
According to React FAQs
You canβt use Hooks inside of a class component, but you can
definitely mix classes and function components with Hooks in a single
tree. Whether a component is a class or a function that uses Hooks is
an implementation detail of that component. In the longer term, we
expect Hooks to be the primary way people write React components.
const MyDiv = () => {
const [sampleState, setState] = useState('hello world');
render(){
return <div>{sampleState}</div>
}
}
You can use the react-universal-hooks library. It lets you use the "useXXX" functions within the render function of class-components.
It's worked great for me so far. The only issue is that since it doesn't use the official hooks, the values don't show react-devtools.
To get around this, I created an equivalent by wrapping the hooks, and having them store their data (using object-mutation to prevent re-renders) on component.state.hookValues. (you can access the component by auto-wrapping the component render functions, to run set currentCompBeingRendered = this)
For more info on this issue (and details on the workaround), see here: https://github.com/salvoravida/react-universal-hooks/issues/7
Stateful components or containers or class-based components ever support the functions of React Hooks, so we don't need to React Hooks in Stateful components just in stateless components.
Some additional informations
What are React Hooks?
So what are hooks? Well hooks are a new way or offer us a new way of writing our components.
Thus far, of course we have functional and class-based components, right? Functional components receive props and you return some JSX code that should be rendered to the screen.
They are great for presentation, so for rendering the UI part, not so much about the business logic and they are typically focused on one or a few purposes per component.
Class-based components on the other hand also will receive props but they also have this internal state. Therefore class-based components are the components which actually hold the majority of our business logic, so with business logic, I mean things like we make an HTTP request and we need to handle the response and to change the internal state of the app or maybe even without HTTP. A user fills out the form and we want to show this somewhere on the screen, we need state for this, we need class-based components for this and therefore we also typically use class based components to orchestrate our other components and pass our state down as props to functional components for example.
Now one problem we have with this separation, with all the benefits it adds but one problem we have is that converting from one component form to the other is annoying. It's not really difficult but it is annoying.
If you ever found yourself in a situation where you needed to convert a functional component into a class-based one, it's a lot of typing and a lot of typing of always the same things, so it's annoying.
A bigger problem in quotation marks is that lifecycle hooks can be hard to use right.
Obviously, it's not hard to add componentDidMount and execute some code in there but knowing which lifecycle hook to use, when and how to use it correctly, that can be challenging especially in more complex applications and anyways, wouldn't it be nice if we had one way of creating components and that super component could then handle both state and side effects like HTTP requests and also render the user interface?
Well, this is exactly what hooks are all about. Hooks give us a new way of creating functional components and that is important.
React Hooks let you use react features and lifecycle without writing a class.
It's like the equivalent version of the class component with much smaller and readable form factor. You should migrate to React hooks because it's fun to write it.
But you can't write react hooks inside a class component, as it's introduced for functional component.
This can be easily converted to :
class MyDiv extends React.component
constructor(){
this.state={sampleState:'hello world'}
}
render(){
return <div>{this.state.sampleState}
}
}
const MyDiv = () => {
const [sampleState, setSampleState] = useState('hello world');
return <div>{sampleState}</div>
}
It won't be possible with your existing class components. You'll have to convert your class component into a functional component and then do something on the lines of -
function MyDiv() {
const [sampleState, setSampleState] = useState('hello world');
return (
<div>{sampleState}</div>
)
}
For me React.createRef() was helpful.
ex.:
constructor(props) {
super(props);
this.myRef = React.createRef();
}
...
<FunctionComponent ref={this.myRef} />
Origin post here.
I've made a library for this. React Hookable Component.
Usage is very simple. Replace extends Component or extends PureComponent with extends HookableComponent or extends HookablePureComponent. You can then use hooks in the render() method.
import { HookableComponent } from 'react-hookable-component';
// ππππππππ
class ComponentThatUsesHook extends HookableComponent<Props, State> {
render() {
// ππππππ
const value = useSomeHook();
return <span>The value is {value}</span>;
}
}
if you didn't need to change your class component then create another functional component and do hook stuff and import it to class component
Doesn't work anymore in modern React Versions. Took me forever, but finally resulted going back to go ol' callbacks. Only thing that worked for me, all other's threw the know React Hook Call (outside functional component) error.
Non-React or React Context:
class WhateverClass {
private xyzHook: (XyzHookContextI) | undefined
public setHookAccessor (xyzHook: XyzHookContextI): void {
this.xyzHook = xyzHook
}
executeHook (): void {
const hookResult = this.xyzHook?.specificHookFunction()
...
}
}
export const Whatever = new WhateverClass() // singleton
Your hook (or your wrapper for an external Hook)
export interface XyzHookContextI {
specificHookFunction: () => Promise<string>
}
const XyzHookContext = createContext<XyzHookContextI>(undefined as any)
export function useXyzHook (): XyzHookContextI {
return useContext(XyzHookContextI)
}
export function XyzHook (props: PropsWithChildren<{}>): JSX.Element | null {
async function specificHookFunction (): Promise<void> {
...
}
const context: XyzHookContextI = {
specificHookFunction
}
// and here comes the magic in wiring that hook up with the non function component context via callback
Whatever.setHookAccessor(context)
return (
< XyzHookContext.Provider value={context}>
{props.children}
</XyzHookContext.Provider>
)
}
Voila, now you can use ANY react code (via hook) from any other context (class components, vanilla-js, β¦)!
(β¦hope I didn't make to many name change mistakes :P)
Yes, but not directly.
Try react-iifc, more details in its readme.
https://github.com/EnixCoda/react-iifc
Try with-component-hooks:
https://github.com/bplok20010/with-component-hooks
import withComponentHooks from 'with-component-hooks';
class MyComponent extends React.Component {
render(){
const props = this.props;
const [counter, set] = React.useState(0);
//TODO...
}
}
export default withComponentHooks(MyComponent)
2.Try react-iifcοΌ https://github.com/EnixCoda/react-iifc
I'd to know if there's any component or helper function to pre-process/transform properties before delivering to the component itself.
I've using the redux's connect function to achieve this behaviour but for components that doesn`t connect to the redux store doesn't make much sense. The following illustrates the ideal solution:
const MyComponent = (props) => { ... }
const propsProcessor = (props) => {
//do something here and return the processed props
}
export default processingProps(propsProcessor)(MyComponent);
This way I could pass an array to the component, group into an json and use it inside the component.
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.