React: Pass a Callback as Props

• You can also pass handler functions or any method that's defined on a React component to a child component. This is how you allow child components to interact with their parent components. You pass methods to a child just like a regular prop. It's assigned a name and you have access to that method name under this.props in the child component.
• Below there are three components outlined in the code editor. The MyApp component is the parent that will render the GetInput and RenderInput child components.

class MyApp extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      inputValue: ''
    }
    this.handleChange = this.handleChange.bind(this);
  }
  handleChange(event) {
    this.setState({
      inputValue: event.target.value
    });
  }
  render() {
    return (
       <div>
        { /* Change code below this line */ }

        { /* Change code above this line */ }
       </div>
    );
  }
};

class GetInput extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    return (
      <div>
        <h3>Get Input:</h3>
        <input
          value={this.props.input}
          onChange={this.props.handleChange}/>
      </div>
    );
  }
};

class RenderInput extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    return (
      <div>
        <h3>Input Render:</h3>
        <p>{this.props.input}</p>
      </div>
    );
  }
};

• What they want us to do is add the GetInput component to the render method in MyApps state. Also create a prop called handleChange and pass the input handler handleChange to it. Next, add RenderInput to the render method in MyApp, then create a prop called input and pass the inputValue from state to it. Once you are finished you will be able to type in the input field in the GetInput component, which then calls the handler method in its parent via props. This updates the input in the state of the parent, which is passed as props to both children.

• Answer:
  

class MyApp extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      inputValue: ''
    }
    this.handleChange = this.handleChange.bind(this);
  }
  handleChange(event) {
    this.setState({
      inputValue: event.target.value
    });
  }
  render() {
    return (
       <div>
        <GetInput handleChange = {this.handleChange} input = {this.state.inputValue} />
        <RenderInput input = {this.state.inputValue}/>
       </div>
    );
  }
};