react-use-sub-state

H1 For example

import React from 'react';
import useSubState from 'useSubState';

class ChildComponent extends Component {
  state = {
    greeting: 'hello, from child component state'
  };

  render() {
    return this.state.greeting;
  }
}

export default useSubState(ChildComponent);

import React from 'react';
import ChildComponent from './ChildComponent';

class ParentComponent extends Component {

  handleClick = () => {
    const { greeting } = ChildComponent.getState();
    console.log(greeting);
  }

  render() {
    return (
			<>
				<ChildComponent />
				<button onClick={this.handleClick}>get sub state</button>
			</>
    );
  }
}

export default ParentComponent;