reactjs - react useEffect 钩子(Hook)和 eslint 警告

Question

我正在寻找有关如何解决以下问题的建议:

我有一个组件 A，它有两个状态，state1 和 state2。

如果我只想在 state1 更改时运行效果，但在 useEFfect 回调中我使用 state2 的值，我该如何解决数组依赖项 eslint react hooks 警告的问题？

例如

function A() {
    const [state1, setState1] = useState(0);
    const [state2, setState2] = useState(0);

    useEffect(() => {
        const a = state1 + state2;
        // do some async logic using a
 
    }, [state1]); //Here eslint react hooks rule requests adding state2 to the dependency array!

return <div> some text </div>

}

Answer 1

常用方法通常是禁用专门针对该行的 linting 规则。

function A() {
  const [state1, setState1] = useState(0);
  const [state2, setState2] = useState(0);

  useEffect(() => {
    // do some async logic using a
    const a = state1 + state2;

    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [state1]);

  return <div> some text </div>;
}

但这里的缺点是，如果依赖项实际上发生变化并且您忘记更新依赖项数组，它可以掩盖依赖项问题。

您可以使用一个 React ref 和一个额外的 useEffect 钩子(Hook)来缓存当前的 state2 值并在另一个 useEffect 回调中引用它.

function A() {
  const [state1, setState1] = useState(0);
  const [state2, setState2] = useState(0);

  const state2Ref = useRef(state2);

  useEffect(() => {
    state2Ref.current = state2;
  }, [state2]);

  useEffect(() => {
    // do some async logic using a
    const a = state1 + state2Ref.current;
  }, [state1]);

  return (
    ...
  );
}

function A() {
  const [state1, setState1] = React.useState(0);
  const [state2, setState2] = React.useState(0);

  const state2Ref = React.useRef(state2);

  React.useEffect(() => {
    state2Ref.current = state2;
  }, [state2]);

  React.useEffect(() => {
    // do some async logic using a
    const a = state1 + state2Ref.current;
    console.log("effect called", a);
  }, [state1]);

  return (
    <div>
      some text
      <div>
        <button type="button" onClick={() => setState1((c) => c + 1)}>
          Update State 1
        </button>
        <button type="button" onClick={() => setState2((c) => c + 1)}>
          Update State 2
        </button>
      </div>
    </div>
  );
}

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

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.2/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.2/umd/react-dom.production.min.js"></script>
<div id="root" />