SimpleComponentWithAlert_v2.jsx

class ParentClass extends React.Component {
  state = {
    alert: undefined
  };

  render() {
    return (
      <SimpleComponentWithAlert renderAlert={this.renderAlert} showAlert={this.showAlert} />
    )
  }

  private renderAlert = () => {
    if (this.state.alert) {
      return <FancyAlertMessage alert={this.state.alert} />
    }
  }

  private showAlert = alert => {
    this.setState({
      alert
    });
  };
}

class SimpleComponentWithAlert extends React.Component {
  render() {
    const myAlert = {
      message: "This is my alert",
      type: "error"
    };
    return (
      <div>
        {this.props.renderAlert()}
        <button onClick={this.props.showAlert(myAlert)}>Show Alert</button>
      </div>
    );
  }
}