Is there any signal that parent component's state set and then child component's state set too?

Question

when parent component set state(itemSelected: item) i want child component set state(isShowForm: true) too, so is there any signal or condition let me do that thing?

<pre>
//this is child Component
class HeaderComponent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      isShowForm: false,
    };
  }

  handleEdit = () =>{
    if(any signal?){
      this.setState({isShowForm:true})
    }
  }
export default HeaderComponent;

//this is parent Component 
class Task extends Component {
  constructor(props){
    super(props);
    this.state = {
      itemSelected: null,
    }
  }
handleEdit = (item) => {
    this.setState({itemSelected: item})
  }
render() {

    let {itemSelected} = this.state;
return(
 HeaderComponent itemSelected={itemSelected}/>
)

</pre>

Answer 1

You can pass the required state from parent component to child and use componentDidUpdate lifecycle in child to listen to the prop and react accordingly.

class HeaderComponent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      isShowForm: false,
    };
  }

  componentDidUpdate(prevProps) =>{
    // Any identifying property to see if the itemSelected object has indeed changed. I'm just assuming that it has a unique ID
    if(prevProps.itemSelected && prevProps.itemSelected.id !== this.props.itemSelected.id) {
      this.setState({ isShowForm: true })
    }
  }
export default HeaderComponent;

//this is parent Component 
class Task extends Component {
  constructor(props){
    super(props);
    this.state = {
      itemSelected: null,
    }
  }
handleEdit = (item) => {
    this.setState({itemSelected: item})
  }
render() {

    let {itemSelected} = this.state;
return(
 <HeaderComponent itemSelected={itemSelected}/>
)