从React组件外部的useReducer检索当前状态

import React, { useReducer } from 'react';

const initialState = { count: 0 };

function reducer(state, action) {
  switch (action.type) {
    case 'increment':
      return { count: state.count + 1 };
    case 'decrement':
      return { count: state.count - 1 };
    default:
      throw new Error();
  }
}

function Counter() {
  const [state, dispatch] = useReducer(reducer, initialState);

  // ...
}

function getCurrentState() {
  return state;
}

function App() {
  const [currentState, setCurrentState] = useState(null);

  function getCurrentState() {
    return currentState;
  }

  return (
    <div>
      <Counter getCurrentState={getCurrentState} />
    </div>
  );
}

function Counter({ getCurrentState }) {
  const [state, dispatch] = useReducer(reducer, initialState);

  useEffect(() => {
    const currentState = getCurrentState();
    console.log(currentState);
  }, []);

  // ...
}