使用刺激性钩子不会更新该值

Question

我在应用程序中使用usepperativeHang Hook来访问propart falue parent component：

const [phone,setPhone]=useState("");
 useImperativeHandle(
    ref,
    () => ({
      type: "text",
      name: "phone",
      value: phone
    }),
    [phone]
  );

当我使用setphone更新手机时，值不会更新。我的实施有什么问题？

Answer 1

usepperativeHandle需要让组件使用forwardRef，一旦这样做，您将能够访问父母的更新ref，因为您将phone作为其依赖关系。

import React, {
  useEffect,
  useState,
  useImperativeHandle,
  forwardRef,
  useRef
} from "react";
import ReactDOM from "react-dom";
import "./styles.css";
const App = forwardRef((props, ref) => {
  const [phone, setPhone] = useState("");
  useImperativeHandle(
    ref,
    () => ({
      type: "text",
      name: "phone",
      value: phone
    }),
    [phone]
  );
  useEffect(() => {
    setTimeout(() => {
      setPhone("9898098909");
    }, 3000);
  }, []);
  return (
    <div className="App">
      <h1>Hello CodeSandbox</h1>
      <h2>Start editing to see some magic happen!</h2>
    </div>
  );
});
const Parent = () => {
  const appRef = useRef(null);
  const handleClick = () => {
    console.log(appRef.current.value);
  };
  return (
    <>
      <App ref={appRef} />
      <button onClick={handleClick}>Click</button>
    </>
  );
};
const rootElement = document.getElementById("root");
ReactDOM.render(<Parent />, rootElement);

工作演示

Answer 2

如果您懒惰并且/或优化在您的应用程序中并不重要，则可以将[{}]的依赖关系传递给useImperativeHandle()，以更新组件重新租赁时，以确保值始终是最新的。

const App = forwardRef((props, ref) => {
  const [phone, setPhone] = useState("");
  useImperativeHandle(
    ref,
    () => ({
      type: "text",
      name: "phone",
      value: phone,
      // other values that you don't have to keep track of via dependency list
    }),
    [{}]
  );