反應 useEffect 鈎子和 eslint 警告

Question

我正在尋找有關如何解決以下問題的建議：

我有一個組件 A，它有兩個狀態，state1 和 state2。

如果我只想在 state1 更改時運行效果，但在 useEFfect 回調中我使用 state2 的值，我該如何解決有關數組依賴 eslint react hooks 警告的問題？

前任。

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

常見的方法通常是禁用專門針對該行的 linting 規則。

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>;
}

但這里的缺點是，如果依賴項實際發生變化並且您忘記更新依賴項數組，它可能會掩蓋依賴項問題。

您可以使用 React ref 和附加的useEffect掛鈎來緩存當前state2值，並在另一個useEffect回調中引用它。

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" />

Answer 2

您需要將// eslint-disable-next-line react-hooks/exhaustive-deps添加到您的 userEffect 中，如下所示：

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

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


       // eslint-disable-next-line react-hooks/exhaustive-deps
    }, [state1]); //Here eslint react hooks rule requests adding state2 to the dependency array!

    return <div> some text </div>

}