【Modern Calendar Datepicker】 不带useState的情况下如何使用？

直接上代码：

import React from "react";
import ReactDOM from "react-dom";

import 'react-persian-calendar-date-picker/lib/DatePicker.css';
import DatePicker from 'react-persian-calendar-date-picker';


import "./styles.css";

class App extends React.Component { 
  state = { selectedDay: null }

  handleDatePickerChange = newValue => {
    this.setState({ selectedDay: newValue });
  }
  render() {
    return (
      <div className="App">
        <h1>Hello CodeSandbox</h1>
        <h2>Start editing to see some magic happen!</h2>
        <DatePicker
        selectedDay={this.state.selectedDay}
        onChange={this.handleDatePickerChange}
        inputPlaceholder="انتخاب روز"
      />
      </div>
    );
  }
}

const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);

参见：https://codesandbox.io/s/jovial-moore-h186k?file=/src/index.js