propDrillingStateChange.js

class Grandmother extends React.Component {
  state = {
    lastName: 'Sanchez'
  }
  
  // When this function is called, the 
  // Grandmother's last name is updated
  immigrateTo = (country, newLastName) => {
    this.setState({ lastName: newLastName })
  }
  
  componentDidMount() {
    this.immigrateTo('US', 'Smith')
  }

  render () {
    // Even though the Grandmother's last name
    // was Sanchez, once her name is changed, 
    // the Mother inherits the name "Smith."
    <Mother lastName={this.state.lastName} />
  }
}