State.js

import React from "react";
import PropTypes from "prop-types";

// Create a State Render Prop Component
class State extends React.Component {
  constructor(props) {
    super(props);
    
    // Initialize state from init prop
    this.state = this.props.init;

    this.handleStateChange = this.handleStateChange.bind(this);
  }

  // Create function to update state
  handleStateChange = state => {
    this.setState(state);
  };

  render() {
    //  Pass handleStateChange and the current state child elements
    return (
      <React.Fragment>
        {this.props.children(this.handleStateChange, this.state)}
      </React.Fragment>
    );
  }
}

State.propTypes = {
  // init must be an object
  init: PropTypes.object,
  // Child function is required
  children: PropTypes.func.isRequired
};

export default State;