React Hooks - useReducer:在触发函数之前等待减速器完成 [英] React Hooks - useReducer: Wait for reducer to finish before triggering a function

问题描述

我有使用 useReducer 钩子的组件:

I have the component using useReducer Hooks:

const init = {
  statA: true,
  statB: true
};

const reducer = (state, action) => {
  switch (action.type) {
    case "ActionA":
      return { ...state, statA: !state.statA };
    case "ActionB":
      return { ...state, statB: !state.statB };
    default:
      return state;
  }
};

const App = () => {
  const [state, dispatch] = useReducer(reducer, init);

  const clickMe = () => {
    dispatch({ type: "ActionA" });
    dispatch({ type: "ActionB" });
    console.log(state);
  }

  return(
      <button onClick={() => clickMe()}>Click Me</button>
  );
};

当按钮被点击时，状态将会改变.但是当我查看日志时，它打印的是以前的状态，而不是当前更新的状态.

When the button is clicked, the state will be changed. But when I view the log, it prints the previous state, not the current updated state.

//On the first click
//Expected
{ statA: false, statB: false }
//Reality
{ statA: true, statB: true }

//On the second click
//Expected
{ statA: true, statB: true }
//Reality
{ statA: false, statB: false }

我知道使用 setState，我可以使用回调来处理更新的状态.但是对于 useReducer，我不知道如何处理更新的状态.有什么办法可以解决我的问题吗?

I know that with setState, I can use callback to work with updated state. But with useReducer, I don't know how to work with the updated state. Is there any way to solve my problem?

推荐答案

console.log(state) 是副作用.副作用属于 useEffect 钩子:

console.log(state) is side effect. Side effects belong to useEffect hook:

  const [state, dispatch] = useReducer(reducer, init);

  useEffect(() => {
    // a condition may be added in case it shouldn't be executed every time
    console.log(state);
  }, [state]);

  const clickMe = () => {
    dispatch({ type: "ActionA" });
    dispatch({ type: "ActionB" });
  }

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