在react状态下存储派生变量不起作用

import React, { useState, useEffect } from 'react';

function MyComponent() {
  const [count, setCount] = useState(0);
  const [derivedValue, setDerivedValue] = useState(0);

  useEffect(() => {
    // 在count变化时更新derivedValue
    setDerivedValue(count * 2);
  }, [count]);

  return (
    <div>
      <p>Count: {count}</p>
      <p>Derived Value: {derivedValue}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

import React, { useState } from 'react';

function MyComponent() {
  const [count, setCount] = useState(0);

  const increment = () => {
    setCount(prevCount => prevCount + 1);
  };

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={increment}>Increment</button>
    </div>
  );
}