How to sync props to state using React hooks : setState()

Solution 1:

useState hooks function argument is being used only once and not everytime the prop changes. You must make use of useEffect hooks to implement what you would call the componentWillReceiveProps/getDerivedStateFromProps functionality

import React,{useState , useEffect} from 'react';

const Persons = (props) =>  {
   const [nameState , setNameState] = useState(props)

   useEffect(() => {
       setNameState(props);
   }, [props])

   return (
            <div>
                <p>My name is {props.name} and my age is {props.age}</p>
                <p>My profession is {props.profession}</p>
            </div>
        )

}

export default Persons;

Solution 2:

The props value in useState(props) is used only during the initial render, further state updates are done with the setter setNameState.

In addition, there is no need for useEffect when updating derived state:

const Person = props => {
  const [nameState, setNameState] = useState(props.name);
  // update derived state conditionally without useEffect
  if (props.name !== nameState) setNameState(props.name);
  // ... other render code
};

From React docs:

[...] you can update the state right during rendering. React will re-run the component with updated state immediately after exiting the first render so it wouldn’t be expensive.

[...] an update during rendering is exactly what getDerivedStateFromProps has always been like conceptually.

In essence, we can optimize performance by getting rid of an additional browser repaint phase, as useEffect always runs after the render is committed to the screen.

Working example

This is a contrived example illustrating above pattern - in real code you would read props.name directly. See the React blog post for more appropriate derived state use cases.

const Person = props => {
  const [nameState, setNameState] = React.useState(props.name);
  // Here, we update derived state without useEffect
  if (props.name !== nameState) setNameState(props.name);

  return (
    <p>
      <h3>Person</h3>
      <div>{nameState} (from derived state)</div>
      <div>{props.name} (from props)</div>
      <p>Note: Derived state is synchronized/contains same value as props.name</p>
    </p>
  );
};

const App = () => {
  const [personName, setPersonName] = React.useState("Lui");
  const changeName = () => setPersonName(personName === "Lukas" ? "Lui" : "Lukas");

  return (
    <div>
      <Person name={personName} />
      <button onClick={changeName}>Change props</button>
    </div>
  );
};

ReactDOM.render(<App />, document.getElementById("root"));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.0/umd/react.production.min.js" integrity="sha256-32Gmw5rBDXyMjg/73FgpukoTZdMrxuYW7tj8adbN8z4=" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.0/umd/react-dom.production.min.js" integrity="sha256-bjQ42ac3EN0GqK40pC9gGi/YixvKyZ24qMP/9HiGW7w=" crossorigin="anonymous"></script>
<div id="root"></div>

Solution 3:

This general idea can be put into hook:

export function useStateFromProp(initialValue) {
  const [value, setValue] = useState(initialValue);

  useEffect(() => setValue(initialValue), [initialValue]);

  return [value, setValue];
}


function MyComponent({ value: initialValue }) {
  const [value, setValue] = useStateFromProp(initialValue);

  return (...);
}

Solution 4:

For that, you need to use the useEffect so your code looks like. As you want to avoid to re-render again if pros didn't change then you have to check first on useEffect and then set the props to current variable.

import React, { useState, useEffect } from "react";

const Persons = props => {
  // console.log(props.name);

  const [nameState, setNameState] = useState(props);

  console.log(nameState.name);
  console.log(props.name);
  useEffect(
    () => {
      if (nameState !== props.name) {
        setNameState(props.name);
      }
    },
    [nameState]
  );
  return (
    <div>
      <p>
        My name is {props.name} and my age is {props.age}
      </p>
      <p>My profession is {props.profession}</p>
    </div>
  );
};

export default Persons;

Demo