{"id":451,"date":"2023-09-26T19:09:05","date_gmt":"2023-09-26T11:09:05","guid":{"rendered":"https:\/\/www.escook.cn\/?p=451"},"modified":"2023-09-26T21:11:00","modified_gmt":"2023-09-26T13:11:00","slug":"react-hooks-usestate-useref-useimperativehandle","status":"publish","type":"post","link":"https:\/\/www.escook.cn\/index.php\/2023\/09\/26\/react-hooks-usestate-useref-useimperativehandle\/","title":{"rendered":"React Hooks – useState & useRef & useImperativeHandle"},"content":{"rendered":"
\n

\u7248\u6743\u5f52\u4f5c\u8005 \u00a9\u5218\u9f99\u5bbe<\/strong> \u6240\u6709\uff0c\u672c\u6587\u7ae0\u672a\u7ecf\u4f5c\u8005\u5141\u8bb8\uff0c\u7981\u6b62\u79c1\u81ea\u8f6c\u8f7d\uff01<\/p>\n<\/blockquote>\n

1. \u51c6\u5907\u5de5\u4f5c<\/h2>\n
    \n
  1. \n

    \u57fa\u4e8e Vite<\/a> \u521b\u5efa React + TypeScript \u7684\u9879\u76ee\uff0c\u5177\u4f53\u521b\u5efa\u9879\u76ee\u7684\u6b65\u9aa4\uff0c\u8bf7\u53c2\u8003 Vite \u5b98\u65b9\u6587\u6863\u3002<\/p>\n<\/li>\n

  2. \n

    \u5728 Vite \u9879\u76ee\u4e2d\u914d\u7f6e @<\/code> \u8def\u5f84\u63d0\u793a<\/p>\n

      \n
    1. \n

      \u5b89\u88c5 node \u7684\u7c7b\u578b\u58f0\u660e\uff1a<\/p>\n

      npm i -D @types\/node<\/code><\/pre>\n<\/li>\n
    2. \n
      \u914d\u7f6e vite.config.ts<\/code> \u6587\u4ef6\uff1a<\/p>\n
      \/\/ 1. \u4ee5 ES6 \u6a21\u5757\u5316\u7684\u65b9\u5f0f\uff0c\u4ece Node \u7684 path \u6a21\u5757\u4e2d\uff0c\u5bfc\u5165 join \u51fd\u6570\nimport { join } from 'path'\n\n\/\/ https:\/\/vitejs.dev\/config\/\nexport default defineConfig({\nplugins: [react()],\n\/\/ 2. \u5728 resolve.alias \u5bf9\u8c61\u4e0b\uff0c\u914d\u7f6e @ \u7684\u6307\u5411\u8def\u5f84\nresolve: {\n  alias: {\n    '@': join(__dirname, '.\/src\/')\n  }\n}\n})<\/code><\/pre>\n<\/li>\n
    3. \n
      \u914d\u7f6e tsconfig.json<\/code> \u6587\u4ef6\uff0c\u5728 compilerOptions<\/code>  \u8282\u70b9\u4e0b\uff0c\u65b0\u589e "baseUrl": "."<\/code> \u548c "paths": { "@\/*": [ "src\/*" ] }<\/code> \u4e24\u9879\uff1a<\/p>\n
      {\n    \"compilerOptions\": {\n      \/* \u65b0\u589e\u4ee5\u4e0b\u4e24\u4e2a\u914d\u7f6e\u9879\uff0c\u5206\u522b\u662f baseUrl \u548c paths *\/\n      \"baseUrl\": \".\",\n      \"paths\": {\n        \"@\/*\": [\n          \"src\/*\"\n        ]\n      },\n      \"target\": \"ES2020\",\n      \"useDefineForClassFields\": true,\n      \"lib\": [\n        \"ES2020\",\n        \"DOM\",\n        \"DOM.Iterable\"\n      ],\n      \"module\": \"ESNext\",\n      \"skipLibCheck\": true,\n      \/* Bundler mode *\/\n      \"moduleResolution\": \"bundler\",\n      \"allowImportingTsExtensions\": true,\n      \"resolveJsonModule\": true,\n      \"isolatedModules\": true,\n      \"noEmit\": true,\n      \"jsx\": \"react-jsx\",\n      \/* Linting *\/\n      \"strict\": true,\n      \"noUnusedLocals\": true,\n      \"noUnusedParameters\": true,\n      \"noFallthroughCasesInSwitch\": true\n    },\n    \"include\": [\n      \"src\"\n    ],\n    \"references\": [\n      {\n        \"path\": \".\/tsconfig.node.json\"\n      }\n    ]\n}<\/code><\/pre>\n<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n
      2. useState<\/h2>\n
      \u57fa\u672c\u7528\u6cd5<\/h3>\n
      useState<\/strong>\uff0c\u80fd\u8ba9\u51fd\u6570\u7ec4\u4ef6\u62e5\u6709\u81ea\u5df1\u7684\u72b6\u6001\uff0c\u56e0\u6b64\uff0c\u5b83\u662f\u4e00\u4e2a\u7ba1\u7406\u72b6\u6001\u7684 hooks API\u3002\u901a\u8fc7 useState \u53ef\u4ee5\u5b9e\u73b0\u72b6\u6001\u7684\u521d\u59cb\u5316\u3001\u8bfb\u53d6\u3001\u66f4\u65b0\u3002\u57fa\u672c\u8bed\u6cd5\u683c\u5f0f\u5982\u4e0b\uff1a<\/p>\n
      const [\u72b6\u6001\u540d, set\u51fd\u6570] = useState(\u521d\u59cb\u503c)<\/code><\/pre>\n
      \u5176\u4e2d\uff1a\u72b6\u6001\u540d\u6240\u4ee3\u8868\u7684\u6570\u636e\uff0c\u53ef\u4ee5\u88ab\u51fd\u6570\u7ec4\u4ef6\u4f7f\u7528\uff1b\u5982\u679c\u8981\u4fee\u6539\u72b6\u6001\u540d\u6240\u4ee3\u8868\u7684\u6570\u636e\uff0c\u9700\u8981\u8c03\u7528 set \u51fd\u6570<\/strong> \u8fdb\u884c\u4fee\u6539\u3002\u4f8b\u5982\uff1a<\/p>\n
      import { useState } from 'react'\n\nexport function Count() {\n  \/\/ \u5b9a\u4e49\u72b6\u6001 count\uff0c\u5176\u521d\u59cb\u503c\u4e3a 0\n  \/\/ \u5982\u679c\u8981\u4fee\u6539 count \u7684\u503c\uff0c\u9700\u8981\u8c03\u7528 setCount(\u65b0\u503c) \u51fd\u6570\n  const [count, setCount] = useState(0)\n\n  return (\n    <>\n      <!-- \u5728\u51fd\u6570\u7ec4\u4ef6\u5185\uff0c\u4f7f\u7528\u540d\u4e3a count \u7684\u72b6\u6001 -->\n      <h1>\u5f53\u524d\u7684 count \u503c\u4e3a\uff1a{count}<\/h1>\n      <!-- \u70b9\u51fb\u6309\u94ae\u65f6\uff0c\u8c03\u7528 setCount() \u51fd\u6570\uff0c\u4e3a count \u8d4b\u65b0\u503c -->\n      <button onClick={() => setCount(count + 1)}>+1<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
      \u72b6\u6001\u53d8\u5316\u65f6\uff0c\u4f1a\u89e6\u53d1\u51fd\u6570\u7ec4\u4ef6\u7684\u91cd\u65b0\u6267\u884c<\/h3>\n
      \u5728\u51fd\u6570\u7ec4\u4ef6\u4e2d\u4f7f\u7528 setState \u5b9a\u4e49\u72b6\u6001\u4e4b\u540e\uff0c\u6bcf\u5f53\u72b6\u6001\u53d1\u751f\u53d8\u5316\uff0c\u90fd\u4f1a\u89e6\u53d1\u51fd\u6570\u7ec4\u4ef6\u7684\u91cd\u65b0\u6267\u884c\uff0c\u4ece\u800c\u6839\u636e\u6700\u65b0\u7684\u6570\u636e\u66f4\u65b0\u6e32\u67d3 DOM \u7ed3\u6784<\/strong>\u3002\u4f8b\u5982\uff1a<\/p>\n
      import { useState } from 'react'\n\nexport function Count() {\n  \/\/ \u5b9a\u4e49\u72b6\u6001 count\uff0c\u5176\u521d\u59cb\u503c\u4e3a 0\n  \/\/ \u5982\u679c\u8981\u4fee\u6539 count \u7684\u503c\uff0c\u9700\u8981\u8c03\u7528 setCount(\u65b0\u503c) \u51fd\u6570\n  const [count, setCount] = useState(0)\n\n  \/\/ \u6bcf\u6b21 count \u503c\u53d1\u751f\u53d8\u5316\uff0c\u90fd\u4f1a\u6253\u5370\u4e0b\u9762\u7684\u8fd9\u53e5\u8bdd\uff1a\n  console.log('\u7ec4\u4ef6\u88ab\u91cd\u65b0\u6e32\u67d3\u4e86')\n\n  const add = () => {\n    setCount(count + 1)\n  }\n\n  return (\n    <>\n      <!-- \u5728\u51fd\u6570\u7ec4\u4ef6\u5185\uff0c\u4f7f\u7528\u540d\u4e3a count \u7684\u72b6\u6001 -->\n      <h1>\u5f53\u524d\u7684 count \u503c\u4e3a\uff1a{count}<\/h1>\n      <!-- \u70b9\u51fb\u6309\u94ae\u65f6\uff0c\u5728 add \u5904\u7406\u51fd\u6570\u4e2d\uff0c\u8c03\u7528 setCount() \u51fd\u6570\uff0c\u4e3a count \u8d4b\u65b0\u503c -->\n      <button onClick={add}>+1<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
      \n
      \u6ce8\u610f\uff1a\u5f53\u51fd\u6570\u5f0f\u7ec4\u4ef6\u88ab\u91cd\u65b0\u6267\u884c\u65f6\uff0c\u4e0d\u4f1a\u91cd\u590d\u8c03\u7528 useState() \u7ed9\u6570\u636e\u8d4b\u521d\u503c\uff0c\u800c\u662f\u4f1a\u590d\u7528\u4e0a\u6b21\u7684 state \u503c\u3002<\/p>\n<\/blockquote>\n
      \u4ee5\u51fd\u6570\u7684\u5f62\u5f0f\u4e3a\u72b6\u6001\u8d4b\u521d\u59cb\u503c<\/h3>\n
      \u5728\u4f7f\u7528 useState \u5b9a\u4e49\u72b6\u6001\u65f6\uff0c\u9664\u4e86\u53ef\u4ee5\u76f4\u63a5\u7ed9\u5b9a\u521d\u59cb\u503c<\/strong>\uff0c\u8fd8\u53ef\u4ee5\u901a\u8fc7\u51fd\u6570\u8fd4\u56de\u503c<\/strong>\u7684\u5f62\u5f0f\uff0c\u4e3a\u72b6\u6001\u8d4b\u521d\u59cb\u503c\uff0c\u8bed\u6cd5\u683c\u5f0f\u5982\u4e0b\uff1a<\/p>\n
      const [value, setValue] = useState(() => \u521d\u59cb\u503c)<\/code><\/pre>\n
      \u4f8b\u5982\uff1a<\/p>\n
      export const DateCom: React.FC = () => {\n  \/\/ const [date] = useState({ year: 2023, month: 9, day: 11 })\n  const [date, setDate] = useState(() => {\n    const dt = new Date()\n    return { year: dt.getFullYear(), month: dt.getMonth() + 1, day: dt.getDate() }\n  })\n\n  return (\n    <>\n      <h1>\u4eca\u65e5\u4fe1\u606f\uff1a<\/h1>\n      <p>\u5e74\u4efd\uff1a{date.year}\u5e74<\/p>\n      <p>\u6708\u4efd\uff1a{date.month}\u6708<\/p>\n      <p>\u65e5\u671f\uff1a{date.day}\u65e5<\/p>\n    <\/>\n  )\n}<\/code><\/pre>\n
      \n
      \u6ce8\u610f\uff1a\u4ee5\u51fd\u6570\u7684\u5f62\u5f0f\u4e3a\u72b6\u6001\u8d4b\u521d\u59cb\u503c\u65f6\uff0c\u53ea\u6709\u7ec4\u4ef6\u9996\u6b21\u88ab\u6e32\u67d3\u624d\u4f1a\u6267\u884c fn \u51fd\u6570\uff1b\u5f53\u7ec4\u4ef6\u88ab\u66f4\u65b0\u65f6\uff0c\u4f1a\u4ee5\u66f4\u65b0\u524d\u7684\u503c\u4f5c\u4e3a\u72b6\u6001\u7684\u521d\u59cb\u503c\uff0c\u8d4b\u521d\u59cb\u503c\u7684\u51fd\u6570\u4e0d\u4f1a\u6267\u884c\u3002<\/p>\n<\/blockquote>\n
      useState \u662f\u5f02\u6b65\u53d8\u66f4\u72b6\u6001\u7684<\/h3>\n
      \u8c03\u7528 useState() \u4f1a\u8fd4\u56de\u4e00\u4e2a\u53d8\u66f4\u72b6\u6001\u7684\u51fd\u6570<\/strong>\uff0c\u8fd9\u4e2a\u51fd\u6570\u5185\u90e8\u662f\u4ee5\u5f02\u6b65\u7684\u5f62\u5f0f<\/strong>\u4fee\u6539\u72b6\u6001\u7684\uff0c\u6240\u4ee5\u4fee\u6539\u72b6\u6001\u540e\u65e0\u6cd5\u7acb\u5373\u62ff\u5230\u6700\u65b0\u7684\u72b6\u6001<\/strong>\uff0c\u4f8b\u5982\uff1a<\/p>\n
      export const Count: React.FC = () => {\n  const [count, setCount] = useState(() => 0)\n\n  const add = () => {\n    \/\/ 1. \u8ba9\u6570\u503c\u81ea\u589e+1\n    setCount(count + 1)\n    \/\/ 2. \u6253\u5370 count \u7684\u503c\n    console.log(count)\n  }\n\n  return (\n    <>\n      <h1>\u5f53\u524d\u7684 count \u503c\u4e3a\uff1a{count}<\/h1>\n      <button onClick={add}>+1<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
      \u5728\u4e0a\u8ff0\u4ee3\u7801\u7684\u7b2c8\u884c\uff0c\u6253\u5370\u51fa\u6765\u7684 count \u503c\u662f\u66f4\u65b0\u524d\u7684\u65e7\u503c\uff0c\u800c\u975e\u66f4\u65b0\u540e\u7684\u65b0\u503c\u3002\u8bc1\u660e useState<\/strong> \u662f\u5f02\u6b65\u53d8\u66f4\u72b6\u6001\u7684\u3002<\/p>\n
      \u7ed3\u5408 useEffect \u76d1\u542c\u72b6\u6001\u7684\u53d8\u5316<\/h3>\n
      \u4e3a\u4e86\u80fd\u591f\u76d1\u542c\u5230\u72b6\u6001\u7684\u53d8\u5316\uff0creact \u63d0\u4f9b\u4e86 useEffect<\/strong> \u51fd\u6570\u3002\u5b83\u80fd\u591f\u76d1\u542c\u4f9d\u8d56\u9879\u72b6\u6001\u7684\u53d8\u5316\uff0c\u5e76\u6267\u884c\u5bf9\u5e94\u7684\u56de\u8c03\u51fd\u6570<\/strong>\u3002\u57fa\u672c\u8bed\u6cd5\u683c\u5f0f\u5982\u4e0b\uff1a<\/p>\n
      useEffect(() => { \/* \u4f9d\u8d56\u9879\u53d8\u5316\u65f6\uff0c\u8981\u89e6\u53d1\u7684\u56de\u8c03\u51fd\u6570 *\/ }, [\u4f9d\u8d56\u9879])<\/code><\/pre>\n
      \u4f8b\u5982\uff1a<\/p>\n
      export const Count: React.FC = () => {\n  const [count, setCount] = useState(() => 0)\n\n  const add = () => {\n    setCount(count + 1)\n  }\n\n  \/\/ \u5f53 count \u53d8\u5316\u540e\uff0c\u4f1a\u89e6\u53d1 useEffect \u6307\u5b9a\u7684\u56de\u8c03\u51fd\u6570\n  useEffect(() => {\n    console.log(count)\n  }, [count])\n\n  return (\n    <>\n      <h1>\u5f53\u524d\u7684 count \u503c\u4e3a\uff1a{count}<\/h1>\n      <button onClick={add}>+1<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
      \n
      \u6ce8\u610f\uff1auseEffect \u4e5f\u662f React \u63d0\u4f9b\u7684 Hooks API\uff0c\u540e\u9762\u7684\u8bfe\u7a0b\u4e2d\u4f1a\u5bf9\u5b83\u8fdb\u884c\u8be6\u7ec6\u7684\u4ecb\u7ecd\u3002<\/p>\n<\/blockquote>\n
      \u6ce8\u610f\u4e8b\u9879<\/h3>\n
      1. \u66f4\u65b0\u5bf9\u8c61\u7c7b\u578b\u7684\u503c<\/h4>\n
      \u5982\u679c\u8981\u66f4\u65b0\u5bf9\u8c61\u7c7b\u578b\u7684\u503c\uff0c\u5e76\u89e6\u53d1\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3\uff0c\u5219\u5fc5\u987b\u4f7f\u7528\u5c55\u5f00\u8fd0\u7b97\u7b26<\/strong>\u6216Object.assign()<\/strong>\u751f\u6210\u4e00\u4e2a\u65b0\u5bf9\u8c61\uff0c\u7528\u65b0\u5bf9\u8c61\u8986\u76d6\u65e7\u5bf9\u8c61\uff0c\u624d\u80fd\u6b63\u5e38\u89e6\u53d1\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3\u3002\u793a\u4f8b\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n
      export const UserInfo: React.FC = () => {\n  const [user, setUser] = useState({\n    name: 'zs',\n    age: 12,\n    gender: '\u7537'\n  })\n\n  const updateUserInfo = () => {\n    user.name = 'Jesse Pinkman'\n    \/\/ \u4e0b\u9762\u7684\u5199\u6cd5\u662f\u9519\u8bef\u7684\uff0c\u56e0\u4e3a set \u51fd\u6570\u5185\u90e8\uff0c\u4f1a\u5bf9\u66f4\u65b0\u524d\u540e\u7684\u503c\u8fdb\u884c\u5bf9\u6bd4\uff1b\n    \/\/ \u7531\u4e8e\u66f4\u65b0\u524d\u540e\u7684 user\uff0c\u539f\u503c\u7684\u5f15\u7528\u548c\u65b0\u503c\u7684\u5f15\u7528\u76f8\u540c\uff0c\n    \/\/ \u6240\u4ee5 react \u8ba4\u4e3a\u503c\u6ca1\u6709\u53d1\u751f\u53d8\u5316\uff0c\u4e0d\u4f1a\u89e6\u53d1\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3\u3002\n    \/\/ setUser(user)\n\n    \/\/ \u89e3\u51b3\u65b9\u6848\uff1a\u7528\u65b0\u5bf9\u8c61\u7684\u5f15\u7528\u66ff\u6362\u65e7\u5bf9\u8c61\u7684\u5f15\u7528\uff0c\u5373\u53ef\u6b63\u5e38\u89e6\u53d1\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3\u3002\n    setUser({ ...user })\n    \/\/ setUser(Object.assign({}, user))\n  }\n\n  return (\n    <>\n      <h1>\u7528\u6237\u4fe1\u606f\uff1a<\/h1>\n      <p>\u59d3\u540d\uff1a{user.name}<\/p>\n      <p>\u5e74\u9f84\uff1a{user.age}<\/p>\n      <p>\u6027\u522b\uff1a{user.gender}<\/p>\n\n      <button onClick={updateUserInfo}>\u66f4\u65b0\u7528\u6237\u4fe1\u606f<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
      2. \u89e3\u51b3\u503c\u66f4\u65b0\u4e0d\u53ca\u65f6\u7684 Bug<\/h4>\n
      \u5f53\u8fde\u7eed\u591a\u6b21\u4ee5\u76f8\u540c\u7684\u64cd\u4f5c<\/strong>\u66f4\u65b0\u72b6\u6001\u503c\u65f6\uff0cReact \u5185\u90e8\u4f1a\u5bf9\u4f20\u9012\u8fc7\u6765\u7684\u65b0\u503c\u8fdb\u884c\u6bd4\u8f83\uff0c\u5982\u679c\u503c\u76f8\u540c\uff0c\u5219\u4f1a\u5c4f\u853d\u540e\u7eed\u7684\u66f4\u65b0\u884c\u4e3a\uff0c\u4ece\u800c\u9632\u6b62\u7ec4\u4ef6\u9891\u7e41\u6e32\u67d3\u7684\u95ee\u9898\u3002\u8fd9\u867d\u7136\u63d0\u9ad8\u4e86\u6027\u80fd\uff0c\u4f46\u4e5f\u5e26\u6765\u4e86\u4e00\u4e2a\u4f7f\u7528\u8bef\u533a\uff0c\u4f8b\u5982\uff1a<\/p>\n
      export const Count: React.FC = () => {\n  const [count, setCount] = useState(() => 0)\n\n  const add = () => {\n    \/\/ 1. \u5e0c\u671b\u8ba9 count \u503c\u4ece 0 \u81ea\u589e\u5230 1\n    setCount(count + 1)\n    \/\/ 2. \u5e0c\u671b\u8ba9 count \u503c\u4ece 1 \u81ea\u589e\u5230 2\n    setCount(count + 1)\n  }\n\n  return (\n    <>\n      <h1>\u5f53\u524d\u7684 count \u503c\u4e3a\uff1a{count}<\/h1>\n      <button onClick={add}>+1<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
      \u7ecf\u8fc7\u6d4b\u8bd5\uff0c\u6211\u4eec\u53d1\u73b0\u4e0a\u8ff0\u4ee3\u7801\u6267\u884c\u7684\u7ed3\u679c\uff0c\u53ea\u662f\u8ba9 count \u4ece 0 \u53d8\u6210\u4e86 1\uff0c\u6700\u7ec8\u7684 count \u503c\u5e76\u4e0d\u662f 2\u3002Why\uff1f<\/p>\n
      \u56e0\u4e3a setCount<\/code> \u662f\u5f02\u6b65\u5730\u66f4\u65b0\u72b6\u6001\u503c\u7684\uff0c\u6240\u4ee5\u524d\u540e\u4e24\u6b21\u8c03\u7528 setCount<\/code> \u4f20\u9012\u8fdb\u53bb\u7684\u65b0\u503c\u90fd\u662f 1\u3002React \u5185\u90e8\u5982\u679c\u9047\u5230\u4e24\u6b21\u76f8\u540c\u7684\u72b6\u6001\uff0c\u5219\u4f1a\u9ed8\u8ba4\u963b\u6b62\u7ec4\u4ef6\u518d\u6b21\u66f4\u65b0\u3002<\/p>\n
      \u4e3a\u4e86\u89e3\u51b3\u4e0a\u8ff0\u7684\u95ee\u9898\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u51fd\u6570\u7684\u65b9\u5f0f<\/strong>\u7ed9\u72b6\u6001\u8d4b\u65b0\u503c\u3002\u5f53\u51fd\u6570\u6267\u884c\u65f6\u624d\u901a\u8fc7\u51fd\u6570\u7684\u5f62\u53c2\uff0c\u62ff\u5230\u5f53\u524d\u7684\u72b6\u6001\u503c\uff0c\u5e76\u57fa\u4e8e\u5b83\u8fd4\u56de\u65b0\u7684\u72b6\u6001\u503c\u3002\u793a\u4f8b\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n
      export const Count: React.FC = () => {\n  const [count, setCount] = useState(() => 0)\n\n  const add = () => {\n    \/\/ \u4f20\u9012\u4e86\u66f4\u65b0\u72b6\u6001\u7684\u51fd\u6570\u8fdb\u53bb\n    setCount((c) => c + 1)\n    setCount((c) => c + 1)\n  }\n\n  return (\n    <>\n      <h1>\u5f53\u524d\u7684 count \u503c\u4e3a\uff1a{count}<\/h1>\n      <button onClick={add}>+1<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
      3. \u4f7f\u7528 setState \u6a21\u62df\u7ec4\u4ef6\u7684\u5f3a\u5236\u5237\u65b0<\/h4>\n
      \u5728\u51fd\u6570\u7ec4\u4ef6\u4e2d\uff0c\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7 useState \u6765\u6a21\u62df forceUpdate \u7684\u5f3a\u5236\u5237\u65b0\u64cd\u4f5c<\/strong>\u3002\u56e0\u4e3a\u53ea\u8981 useState \u7684\u72b6\u6001\u53d1\u751f\u4e86\u53d8\u5316\uff0c\u5c31\u4f1a\u89e6\u53d1\u51fd\u6570\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3\uff0c\u4ece\u800c\u8fbe\u5230\u5f3a\u5236\u5237\u65b0\u7684\u76ee\u7684\u3002\u5177\u4f53\u7684\u4ee3\u7801\u793a\u4f8b\u5982\u4e0b\uff1a<\/p>\n
      export const FUpdate: React.FC = () => {\n  const [, forceUpdate] = useState({})\n\n  \/\/ \u6bcf\u6b21\u8c03\u7528 onRefresh \u51fd\u6570\uff0c\u90fd\u4f1a\u7ed9 forceUpdate \u4f20\u9012\u4e00\u4e2a\u65b0\u5bf9\u8c61\n  \/\/ \u4ece\u800c\u89e6\u53d1\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3\n  const onRefresh = () => forceUpdate({})\n\n  return (\n    <>\n      <button onClick={onRefresh}>\u70b9\u51fb\u5f3a\u5236\u5237\u65b0 --- {Date.now()}<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
      \n
      \u6ce8\u610f\uff1a\u56e0\u4e3a\u6bcf\u6b21\u4f20\u5165\u7684\u5bf9\u8c61\u7684\u5730\u5740\u4e0d\u540c\uff0c\u6240\u4ee5\u4e00\u5b9a\u4f1a\u4f7f\u7ec4\u4ef6\u5237\u65b0\u3002<\/p>\n<\/blockquote>\n
      3. useRef<\/h2>\n
      useRef \u51fd\u6570\u8fd4\u56de\u4e00\u4e2a\u53ef\u53d8\u7684 ref \u5bf9\u8c61\uff0c\u8be5\u5bf9\u8c61\u53ea\u6709\u4e00\u4e2a current<\/strong> \u5c5e\u6027\u3002\u53ef\u4ee5\u5728\u8c03\u7528 useRef \u51fd\u6570\u65f6\u4e3a\u5176\u6307\u5b9a\u521d\u59cb\u503c\u3002\u5e76\u4e14\u8fd9\u4e2a\u8fd4\u56de\u7684 ref \u5bf9\u8c61\u5728\u7ec4\u4ef6\u7684\u6574\u4e2a\u751f\u547d\u5468\u671f\u5185\u4fdd\u6301\u4e0d\u53d8\u3002\u8bed\u6cd5\u683c\u5f0f\u5982\u4e0b\uff1a<\/p>\n
      \/\/ 1. \u5bfc\u5165 useRef\nimport { useRef } from 'react'\n\/\/ 2. \u8c03\u7528 useRef \u521b\u5efa ref \u5bf9\u8c61\nconst refObj = useRef(\u521d\u59cb\u503c)\n\/\/ 3. \u901a\u8fc7 ref.current \u8bbf\u95ee ref \u4e2d\u5b58\u50a8\u7684\u503c\nconsole.log(refObj.current)<\/code><\/pre>\n
      useRef \u51fd\u6570\u7528\u6765\u89e3\u51b3\u4ee5\u4e0b\u4e24\u4e2a\u95ee\u9898\uff1a<\/p>\n
        \n
      1. \u83b7\u53d6 DOM \u5143\u7d20<\/strong>\u6216\u5b50\u7ec4\u4ef6<\/strong>\u7684\u5b9e\u4f8b\u5bf9\u8c61\uff1b<\/li>\n
      2. \u5b58\u50a8\u6e32\u67d3\u5468\u671f\u4e4b\u95f4\u5171\u4eab\u7684\u6570\u636e<\/strong>\uff1b<\/li>\n<\/ol>\n
        \u83b7\u53d6 DOM\u5143\u7d20\u7684\u5b9e\u4f8b<\/h3>\n
        \u4e0b\u9762\u7684\u4ee3\u7801\u6f14\u793a\u4e86\u5982\u4f55\u83b7\u53d6 Input \u5143\u7d20\u7684\u5b9e\u4f8b\uff0c\u5e76\u8c03\u7528\u5176 DOM API\u3002<\/p>\n
        import React, { useRef } from 'react'\n\nexport const InputFocus: React.FC = () => {\n  \/\/ 1. \u521b\u5efa ref \u5f15\u7528\n  const iptRef = useRef<HTMLInputElement>(null)\n\n  const getFocus = () => {\n    \/\/ 3. \u8c03\u7528 focus API\uff0c\u8ba9\u6587\u672c\u6846\u83b7\u53d6\u7126\u70b9\n    iptRef.current?.focus()\n  }\n\n  return (\n    <>\n      {\/* 2. \u7ed1\u5b9a ref \u5f15\u7528 *\/}\n      <input type="text" ref={iptRef} \/>\n      <button onClick={getFocus}>\u70b9\u51fb\u83b7\u53d6\u7126\u70b9<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
        \u5b58\u50a8\u6e32\u67d3\u5468\u671f\u4e4b\u95f4\u7684\u5171\u4eab\u6570\u636e<\/h3>\n
        \u57fa\u4e8e useRef \u521b\u5efa\u540d\u4e3a prevCountRef<\/code> \u7684\u6570\u636e\u5bf9\u8c61\uff0c\u7528\u6765\u5b58\u50a8\u4e0a\u4e00\u6b21\u7684\u65e7 count \u503c\u3002\u6bcf\u5f53\u70b9\u51fb\u6309\u94ae\u89e6\u53d1 count \u81ea\u589e\u65f6\uff0c\u90fd\u628a\u6700\u65b0\u7684\u65e7\u503c\u8d4b\u503c\u7ed9 prevCountRef.current<\/code> \u5373\u53ef\uff1a<\/p>\n
        export const Counter: React.FC = () => {\n  \/\/ \u9ed8\u8ba4\u503c\u4e3a 0\n  const [count, setCount] = useState(0)\n\n  \/\/ \u9ed8\u8ba4\u503c\u4e3a undefined\n  const prevCountRef = useRef<number>()\n\n  const add = () => {\n    \/\/ \u70b9\u51fb\u6309\u94ae\u65f6\uff0c\u8ba9 count \u503c\u5f02\u6b65 +1\n    setCount((c) => c + 1)\n    \/\/ \u540c\u65f6\uff0c\u628a count \u6240\u4ee3\u8868\u7684\u65e7\u503c\u8bb0\u5f55\u5230 prevCountRef \u4e2d\n    prevCountRef.current = count\n  }\n\n  return (\n    <>\n      <h1>\n        \u65b0\u503c\u662f\uff1a{count}\uff0c\u65e7\u503c\u662f\uff1a{prevCountRef.current}\n      <\/h1>\n      <button onClick={add}>+1<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
        \u6ce8\u610f\u4e8b\u9879<\/h3>\n
        1. \u7ec4\u4ef6 rerender \u65f6 useRef \u4e0d\u4f1a\u88ab\u91cd\u590d\u521d\u59cb\u5316<\/h4>\n
        \u5728 RefTimer<\/strong> \u7ec4\u4ef6\u4e2d\uff0c\u70b9\u51fb +1 \u6309\u94ae<\/strong>\uff0c\u4f1a\u8ba9 count \u503c\u81ea\u589e\uff0c\u4ece\u800c\u89e6\u53d1 RefTimer \u7ec4\u4ef6\u7684 rerender<\/strong>\u3002\u4f46\u662f\uff0c\u6211\u4eec\u53d1\u73b0 RefTimer \u7ec4\u4ef6\u4e2d\u7684\u65f6\u95f4\u6233\u4fdd\u6301\u4e0d\u53d8\uff0c\u8fd9\u8bf4\u660e\u7ec4\u4ef6\u6bcf\u6b21\u6e32\u67d3\uff0c\u4e0d\u4f1a\u91cd\u590d\u8c03\u7528 useRef \u51fd\u6570\u8fdb\u884c\u521d\u59cb\u5316<\/strong>\u3002\u793a\u4f8b\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n
        export const RefTimer: React.FC = () => {\n  const [count, setCount] = useState(0)\n  const time = useRef(Date.now())\n\n  console.log('\u7ec4\u4ef6\u88ab\u6e32\u67d3\u4e86')\n\n  return (\n    <>\n      <h3>\n        count\u503c\u662f\uff1a{count}, \u65f6\u95f4\u6233\u662f\uff1a{time.current}\n      <\/h3>\n      <button onClick={() => setCount((prev) => prev + 1)}>+1<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
        2. ref.current \u53d8\u5316\u65f6\u4e0d\u4f1a\u9020\u6210\u7ec4\u4ef6\u7684 rerender<\/h4>\n
        \u70b9\u51fb\u7ed9 ref \u8d4b\u65b0\u503c<\/strong>\u7684\u6309\u94ae\u65f6\uff0c\u4e3a time.current<\/code> \u8d4b\u65b0\u503c\uff0c\u6267\u884c\u7684\u7ed3\u679c\u662f\uff1a<\/p>\n
          \n
        1. \u7ec8\u7aef\u4e2d\u8f93\u51fa\u4e86\u6700\u65b0\u7684 time.current<\/code> \u7684\u503c<\/li>\n
        2. \u6ca1\u6709\u89e6\u53d1 RefTimer<\/strong> \u7ec4\u4ef6\u7684 rerender<\/li>\n<\/ol>\n
          \u8fd9\u8bc1\u660e\u4e86 ref.current \u53d8\u5316\u65f6\u4e0d\u4f1a\u9020\u6210\u7ec4\u4ef6\u7684 rerender\uff0c\u793a\u4f8b\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n
          export const RefTimer: React.FC = () => {\n  const [count, setCount] = useState(0)\n  const time = useRef(Date.now())\n\n  const updateTime = () => {\n    time.current = Date.now()\n    console.log(time.current)\n  }\n\n  console.log('\u7ec4\u4ef6\u88ab\u6e32\u67d3\u4e86')\n\n  return (\n    <>\n      <h3>\n        count\u503c\u662f\uff1a{count}, \u65f6\u95f4\u6233\u662f\uff1a{time.current}\n      <\/h3>\n      <button onClick={() => setCount((prev) => prev + 1)}>+1<\/button>\n      <button onClick={updateTime}>\u7ed9ref\u8d4b\u65b0\u503c<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
          3. ref.current \u4e0d\u80fd\u4f5c\u4e3a\u5176\u5b83 Hooks \u7684\u4f9d\u8d56\u9879<\/h4>\n
          \u7531\u4e8e ref.current \u503c\u7684\u53d8\u5316\u4e0d\u4f1a\u9020\u6210\u7ec4\u4ef6\u7684 rerender\uff0c\u800c\u4e14 React \u4e5f\u4e0d\u4f1a\u8ddf\u8e2a ref.current \u7684\u53d8\u5316\uff0c\u56e0\u6b64 ref.current \u4e0d\u53ef\u4ee5\u4f5c\u4e3a\u5176\u5b83 hooks\uff08useMemo\u3001useCallback\u3001useEffect \u7b49\uff09 \u7684\u4f9d\u8d56\u9879\u3002<\/p>\n
          export const RefTimer: React.FC = () => {\n  const [count, setCount] = useState(0)\n  const time = useRef(Date.now())\n\n  const updateTime = () => {\n    time.current = Date.now()\n    console.log(time.current)\n  }\n\n  console.log('\u7ec4\u4ef6\u88ab\u6e32\u67d3\u4e86')\n\n  useEffect(() => {\n    console.log('time \u7684\u503c\u53d1\u751f\u4e86\u53d8\u5316\uff1a' + time.current)\n  }, [time.current])\n\n  return (\n    <>\n      <h3>\n        count\u503c\u662f\uff1a{count}, \u65f6\u95f4\u6233\u662f\uff1a{time.current}\n      <\/h3>\n      <button onClick={() => setCount((prev) => prev + 1)}>+1<\/button>\n      <button onClick={updateTime}>\u7ed9ref\u8d4b\u65b0\u503c<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
          \u5728\u4e0a\u9762\u7684\u4ee3\u7801\u4e2d\uff0c\u7ec4\u4ef6\u9996\u6b21\u6e32\u67d3\u5b8c\u6210\u540e\uff0c\u5fc5\u7136\u4f1a\u89e6\u53d1\u4e00\u6b21 useEffect \u7684\u6267\u884c\u3002\u4f46\u662f\uff0c\u5f53 time.current \u53d1\u751f\u53d8\u5316\u65f6\uff0c\u5e76\u4e0d\u4f1a\u89e6\u53d1 useEffect \u7684\u91cd\u65b0\u6267\u884c\u3002\u56e0\u6b64\uff0c\u4e0d\u80fd\u628a ref.current \u4f5c\u4e3a\u5176\u5b83 hooks \u7684\u4f9d\u8d56\u9879\u3002<\/p>\n
          4. forwardRef<\/h2>\n
          ref \u7684\u4f5c\u7528\u662f\u83b7\u53d6\u5b9e\u4f8b\uff0c\u4f46\u7531\u4e8e\u51fd\u6570\u7ec4\u4ef6\u4e0d\u5b58\u5728\u5b9e\u4f8b\uff0c\u56e0\u6b64\u65e0\u6cd5\u901a\u8fc7 ref \u83b7\u53d6\u51fd\u6570\u7ec4\u4ef6\u7684\u5b9e\u4f8b\u5f15\u7528\u3002\u800c React.forwardRef<\/code> \u5c31\u662f\u7528\u6765\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u7684\u3002<\/p>\n
          React.forwardRef<\/code> \u4f1a\u521b\u5efa\u4e00\u4e2a React \u7ec4\u4ef6\uff0c\u8fd9\u4e2a\u7ec4\u4ef6\u80fd\u591f\u5c06\u5176\u63a5\u6536\u5230\u7684 ref \u5c5e\u6027\u8f6c\u53d1\u5230\u81ea\u5df1\u7684\u7ec4\u4ef6\u6811\u3002<\/p>\n
          \u65e0\u6cd5\u76f4\u63a5\u4f7f\u7528 ref \u5f15\u7528\u51fd\u6570\u5f0f\u7ec4\u4ef6<\/h3>\n
          \u5728\u4e0b\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u7236\u7ec4\u4ef6 Father<\/strong> \u60f3\u901a\u8fc7 ref \u5f15\u7528\u5b50\u7ec4\u4ef6 Child<\/strong>\uff0c\u6b64\u65f6\u4ee3\u7801\u4f1a\u62a5\u9519\uff0c\u56e0\u4e3a\u51fd\u6570\u5f0f\u7ec4\u4ef6\u6ca1\u6709\u5b9e\u4f8b\u5bf9\u8c61\uff0c\u65e0\u6cd5\u88ab\u76f4\u63a5\u5f15\u7528\uff1a<\/p>\n
          \/\/ \u7236\u7ec4\u4ef6\nexport const Father: React.FC = () => {\n  const childRef = useRef()\n\n  return (\n    <>\n      <h1>Father \u7236\u7ec4\u4ef6<\/h1>\n      <hr \/>\n      <!-- \u4e0b\u9762\u8fd9\u884c\u4ee3\u7801\u4e2d\u7684 ref \u4f7f\u7528\u4e0d\u6b63\u786e\uff0c\u56e0\u4e3a Child \u7ec4\u4ef6\u662f\u51fd\u6570\u5f0f\u7ec4\u4ef6\uff0c\u65e0\u6cd5\u88ab\u76f4\u63a5\u5f15\u7528 -->\n      <Child ref={childRef} \/>\n    <\/>\n  )\n}<\/code><\/pre>\n
          Child \u7ec4\u4ef6\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n
          \/\/ \u5b50\u7ec4\u4ef6\uff08\u5b9e\u73b0\u70b9\u51fb\u6309\u94ae\uff0c\u6570\u503c\u52a0\u51cf\u7684\u64cd\u4f5c\uff09\nconst Child: React.FC = () => {\n  const [count, setCount] = useState(0)\n\n  const add = (step: number) => {\n    setCount((prev) => (prev += step))\n  }\n\n  return (\n    <>\n      <h3>Child \u5b50\u7ec4\u4ef6 {count}<\/h3>\n      <button onClick={() => add(-1)}>-1<\/button>\n      <button onClick={() => add(1)}>+1<\/button>\n    <\/>\n  )\n}<\/code><\/pre>\n
          \u6ce8\u610f\uff1a\u4e0a\u9762\u7684\u4ee3\u7801\u65e0\u6cd5\u6b63\u5e38\u8fd0\u884c\uff0c\u4f1a\u5728\u7ec8\u7aef\u63d0\u793a\u5982\u4e0b\u7684 Warning \u8b66\u544a\uff1a<\/p>\n
          Warning: \nFunction components cannot be given refs. Attempts to access this ref will fail. \nDid you mean to use React.forwardRef()?<\/code><\/pre>\n
          \n
          \u9519\u8bef\u63d0\u793a\u4e2d\u6709\u89e3\u51b3\u6b64\u95ee\u9898\u7684\u5173\u952e\u63d0\u793a\uff1aDid you mean to use React.forwardRef()<\/strong>?<\/p>\n<\/blockquote>\n
          forwardRef \u7684\u57fa\u672c\u4f7f\u7528<\/h3>\n
          \u5728\u4f7f\u7528\u51fd\u6570\u7ec4\u4ef6\u65f6\uff0c\u6211\u4eec\u65e0\u6cd5\u76f4\u63a5\u4f7f\u7528 ref \u5f15\u7528\u51fd\u6570\u5f0f\u7ec4\u4ef6\uff0c\u4e0b\u9762\u7684\u4ee3\u7801\u4f1a\u4ea7\u751f\u62a5\u9519\uff1a<\/p>\n
          const childRef = useRef(null)\nreturn <Child ref={inputRef} \/><\/code><\/pre>\n
          \u56e0\u4e3a\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0c\u4f60\u81ea\u5df1\u7684\u7ec4\u4ef6\u4e0d\u4f1a\u66b4\u9732\u5b83\u4eec\u5185\u90e8 DOM \u8282\u70b9\u7684 ref\u3002<\/p>\n
          \u6b63\u786e\u7684\u65b9\u6cd5\u662f\u4f7f\u7528 React.forwardRef()<\/code> \u628a\u51fd\u6570\u5f0f\u7ec4\u4ef6\u5305\u88c5\u8d77\u6765\uff0c\u4f8b\u5982 Child \u5b50\u7ec4\u4ef6\u7684\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n
          \/\/ \u88ab\u5305\u88c5\u7684\u51fd\u6570\u5f0f\u7ec4\u4ef6\uff0c\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f props\uff0c\u7b2c\u4e8c\u4e2a\u53c2\u6570\u662f\u8f6c\u53d1\u8fc7\u6765\u7684 ref\nconst Child = React.forwardRef((props, ref) => {\n  \/\/ \u7701\u7565\u5b50\u7ec4\u4ef6\u5185\u90e8\u7684\u5177\u4f53\u5b9e\u73b0\n})<\/code><\/pre>\n
          \u7136\u540e\uff0c\u5728\u7236\u7ec4\u4ef6 Father \u4e2d\uff0c\u5c31\u53ef\u4ee5\u7ed9\u5b50\u7ec4\u4ef6 Child \u7ed1\u5b9a ref \u4e86\uff1a<\/p>\n
          \/\/ \u7236\u7ec4\u4ef6\nexport const Father: React.FC = () => {\n  const childRef = useRef()\n\n  \/\/ \u6309\u94ae\u7684\u70b9\u51fb\u4e8b\u4ef6\u5904\u7406\u51fd\u6570\n  const onShowRef = () => {\n    console.log(childRef.current)\n  }\n\n  return (\n    <>\n      <h1>Father \u7236\u7ec4\u4ef6<\/h1>\n      {\/* \u70b9\u51fb\u6309\u94ae\uff0c\u6253\u5370 ref \u7684\u503c *\/}\n      <button onClick={onShowRef}>show Ref<\/button>\n      <hr \/>\n      <Child ref={childRef} \/>\n    <\/>\n  )\n}<\/code><\/pre>\n
          \n
          \u6ce8\u610f\uff1a\u6b64\u65f6\u7236\u7ec4\u4ef6 Father \u4e2d\u83b7\u53d6\u5230\u7684 ref.current \u662f null\uff0c\u56e0\u4e3a\u5b50\u7ec4\u4ef6 Child \u6ca1\u6709\u5411\u5916\u66b4\u9732\u4efb\u4f55\u81ea\u5df1\u5185\u90e8\u7684\u4e1c\u897f\u3002<\/p>\n<\/blockquote>\n
          5. useImperativeHandle<\/h2>\n
          \u76f4\u63a5\u4f7f\u7528 ref \u83b7\u53d6 DOM \u5b9e\u4f8b\uff0c\u4f1a\u5168\u9762\u66b4\u9732 DOM \u5b9e\u4f8b\u4e0a\u7684 API\uff0c\u4ece\u800c\u5bfc\u81f4\u5916\u90e8\u4f7f\u7528 ref \u65f6\u6709\u66f4\u5927\u7684\u81ea\u7531\u5ea6\u3002\u5728\u5b9e\u9645\u5f00\u53d1\u4e2d\uff0c\u6211\u4eec\u5e94\u8be5\u4e25\u683c\u63a7\u5236 ref \u7684\u66b4\u9732\u9897\u7c92\u5ea6\uff0c\u63a7\u5236\u5b83\u80fd\u8c03\u7528\u7684\u65b9\u6cd5\uff0c\u53ea\u5411\u5916\u66b4\u9732\u4e3b\u8981\u7684\u529f\u80fd\u51fd\u6570\uff0c\u5176\u5b83\u529f\u80fd\u51fd\u6570\u4e0d\u66b4\u9732\u3002<\/p>\n
          React \u5b98\u65b9\u63d0\u4f9b useImperativeHandle \u7684\u76ee\u7684\uff0c\u5c31\u662f\u8ba9\u4f60\u5728\u4f7f\u7528 ref \u65f6\u53ef\u4ee5\u81ea\u5b9a\u4e49\u66b4\u9732\u7ed9\u5916\u90e8\u7ec4\u4ef6\u54ea\u4e9b\u529f\u80fd\u51fd\u6570\u6216\u5c5e\u6027\u3002<\/p>\n
          \u5b83\u7684\u8bed\u6cd5\u7ed3\u6784\u5982\u4e0b\uff1a<\/p>\n
          useImperativeHandle(\u901a\u8fc7forwardRef\u63a5\u6536\u5230\u7684\u7236\u7ec4\u4ef6\u7684ref\u5bf9\u8c61, () => \u81ea\u5b9a\u4e49ref\u5bf9\u8c61, [\u4f9d\u8d56\u9879\u6570\u7ec4])<\/code><\/pre>\n
          \u5176\u4e2d\uff0c\u7b2c\u4e09\u4e2a\u53c2\u6570\uff08\u4f9d\u8d56\u9879\u6570\u7ec4\uff09\u662f\u53ef\u9009\u7684\u3002<\/p>\n
          useImperativeHandle \u7684\u57fa\u672c\u4f7f\u7528<\/h3>\n
          \u5728\u88ab React.forwardRef()<\/code> \u5305\u88f9\u7684\u7ec4\u4ef6\u4e2d\uff0c\u9700\u8981\u7ed3\u5408 useImperativeHandle<\/code> \u8fd9\u4e2a hooks API\uff0c\u5411\u5916\u6309\u9700\u66b4\u9732\u5b50\u7ec4\u4ef6\u5185\u7684\u6210\u5458\uff1a<\/p>\n
          import React, { useRef, useState, useImperativeHandle } from 'react'\n\n\/\/ \u5b50\u7ec4\u4ef6\nconst Child = React.forwardRef((_, ref) => {\n  const [count, setCount] = useState(0)\n\n  const add = (step: number) => {\n    setCount((prev) => (prev += step))\n  }\n\n  \/\/ 1. \u5411\u5916\u66b4\u9732\u4e00\u4e2a\u7a7a\u5bf9\u8c61\n  \/\/ 2. useImperativeHandle(ref, () => ({}))\n  \/\/ \u5411\u5916\u66b4\u9732\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5176\u4e2d\u5305\u542b\u4e86 name \u548c age \u4e24\u4e2a\u5c5e\u6027\n  useImperativeHandle(ref, () => ({\n    name: 'liulongbin',\n    age: 22\n  }))\n\n  return (\n    <>\n      <h3>Child \u5b50\u7ec4\u4ef6 {count}<\/h3>\n      <button onClick={() => add(-1)}>-1<\/button>\n      <button onClick={() => add(1)}>+1<\/button>\n    <\/>\n  )\n})<\/code><\/pre>\n
          \u57fa\u4e8e useImperativeHandle \u6309\u9700\u5411\u5916\u66b4\u9732\u6210\u5458<\/h3>\n
          \u5728\u5b50\u7ec4\u4ef6\u4e2d\uff0c\u5411\u5916\u66b4\u9732 count \u548c setCount \u8fd9\u4e24\u4e2a\u6210\u5458\uff1a<\/p>\n
          \/\/ \u5b50\u7ec4\u4ef6\nconst Child = React.forwardRef((_, ref) => {\n  const [count, setCount] = useState(0)\n\n  const add = (step: number) => {\n    setCount((prev) => (prev += step))\n  }\n\n  \/\/ \u5411\u5916\u66b4\u9732 count \u7684\u503c\u548c setCount \u51fd\u6570\n  useImperativeHandle(ref, () => ({\n    count,\n    setCount\n  }))\n\n  return (\n    <>\n      <h3>Child \u5b50\u7ec4\u4ef6 {count}<\/h3>\n      <button onClick={() => add(-1)}>-1<\/button>\n      <button onClick={() => add(1)}>+1<\/button>\n    <\/>\n  )\n})<\/code><\/pre>\n
          \u5728\u7236\u7ec4\u4ef6\u4e2d\uff0c\u6dfb\u52a0\u4e00\u4e2a\u91cd\u7f6e\u6309\u94ae\uff0c\u5f53\u70b9\u51fb\u91cd\u7f6e\u6309\u94ae\u65f6\uff0c\u8c03\u7528 ref \u5411\u5916\u66b4\u9732\u7684 setCount \u51fd\u6570\uff0c\u628a\u5b50\u7ec4\u4ef6\u5185\u90e8\u7684 count \u91cd\u7f6e\u4e3a 0\u3002\u793a\u4f8b\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n
          \/\/ \u7236\u7ec4\u4ef6\nexport const Father: React.FC = () => {\n  const childRef = useRef<{ count: number; setCount: (value: number) => void }>(null)\n\n  \/\/ \u6309\u94ae\u7684\u70b9\u51fb\u4e8b\u4ef6\u5904\u7406\u51fd\u6570\n  const onShowRef = () => {\n    console.log(childRef.current)\n  }\n\n  \/\/ \u91cd\u7f6e\u6309\u94ae\u7684\u70b9\u51fb\u4e8b\u4ef6\u5904\u7406\u51fd\u6570\n  const onReset = () => {\n    childRef.current?.setCount(0)\n  }\n\n  return (\n    <>\n      <h1>Father \u7236\u7ec4\u4ef6<\/h1>\n      {\/* \u70b9\u51fb\u6309\u94ae\uff0c\u6253\u5370 ref \u7684\u503c *\/}\n      <button onClick={onShowRef}>show Ref<\/button>\n      {\/* \u70b9\u51fb\u6309\u94ae\uff0c\u91cd\u7f6e\u6570\u636e\u4e3a 0 *\/}\n      <button onClick={onReset}>\u91cd\u7f6e<\/button>\n      <hr \/>\n      <Child ref={childRef} \/>\n    <\/>\n  )\n}<\/code><\/pre>\n
          \u63a7\u5236\u6210\u5458\u66b4\u9732\u7684\u7c92\u5ea6<\/h3>\n
          \u5728 Child \u5b50\u7ec4\u4ef6\u4e2d\uff0c\u6211\u4eec\u5e0c\u671b\u5bf9\u5916\u66b4\u9732\u4e00\u4e2a\u91cd\u7f6e count<\/code> \u4e3a 0 \u7684\u51fd\u6570\uff0c\u800c\u4e0d\u5e0c\u671b\u76f4\u63a5\u628a setCount()<\/code> \u66b4\u9732\u51fa\u53bb\uff0c\u56e0\u4e3a\u7236\u7ec4\u4ef6\u8c03\u7528 setCount()<\/code> \u65f6\u53ef\u4ee5\u4f20\u4efb\u4f55\u6570\u503c\u3002\u56e0\u6b64\uff0c\u6211\u4eec\u53ef\u4ee5\u57fa\u4e8e useImperativeHandle\uff0c\u5411\u5916\u63d0\u4f9b\u4e00\u4e2a reset()<\/code> \u51fd\u6570\u800c\u975e\u76f4\u63a5\u628a setCount()<\/code> \u66b4\u9732\u51fa\u53bb\uff1a<\/p>\n
          \/\/ \u5b50\u7ec4\u4ef6\nconst Child = React.forwardRef((_, ref) => {\n  const [count, setCount] = useState(0)\n\n  const add = (step: number) => {\n    setCount((prev) => (prev += step))\n  }\n\n  \/\/ \u5411\u5916\u66b4\u9732 count \u7684\u503c\u548c reset \u51fd\u6570\n  useImperativeHandle(ref, () => ({\n    count,\n    \/\/ \u5728\u7ec4\u4ef6\u5185\u90e8\u5c01\u88c5\u4e00\u4e2a\u91cd\u7f6e\u4e3a 0 \u7684\u51fd\u6570\uff0cAPI \u7684\u7c92\u5ea6\u66f4\u5c0f\n    reset: () => setCount(0)\n  }))\n\n  return (\n    <>\n      <h3>Child \u5b50\u7ec4\u4ef6 {count}<\/h3>\n      <button onClick={() => add(-1)}>-1<\/button>\n      <button onClick={() => add(1)}>+1<\/button>\n    <\/>\n  )\n})<\/code><\/pre>\n
          \u5728\u7236\u7ec4\u4ef6\u4e2d\uff0c\u8c03\u7528 ref.current.reset() \u5373\u53ef\u628a\u6570\u636e\u91cd\u7f6e\u4e3a 0\uff1a<\/p>\n
          \/\/ \u7236\u7ec4\u4ef6\nexport const Father: React.FC = () => {\n  const childRef = useRef<{ count: number; reset: () => void }>(null)\n\n  \/\/ \u6309\u94ae\u7684\u70b9\u51fb\u4e8b\u4ef6\u5904\u7406\u51fd\u6570\n  const onShowRef = () => {\n    console.log(childRef.current)\n  }\n\n  \/\/ \u91cd\u7f6e\u6309\u94ae\u7684\u70b9\u51fb\u4e8b\u4ef6\u5904\u7406\u51fd\u6570\n  const onReset = () => {\n    childRef.current?.reset()\n  }\n\n  return (\n    <>\n      <h1>Father \u7236\u7ec4\u4ef6<\/h1>\n      {\/* \u70b9\u51fb\u6309\u94ae\uff0c\u6253\u5370 ref \u7684\u503c *\/}\n      <button onClick={onShowRef}>show Ref<\/button>\n      {\/* \u70b9\u51fb\u6309\u94ae\uff0c\u91cd\u7f6e\u6570\u636e\u4e3a 0 *\/}\n      <button onClick={onReset}>\u91cd\u7f6e<\/button>\n      <hr \/>\n      <Child ref={childRef} \/>\n    <\/>\n  )\n}<\/code><\/pre>\n
          useImperativeHandle \u7684\u7b2c\u4e09\u4e2a\u53c2\u6570<\/h3>\n
          \u518d\u6765\u56de\u987e\u4e00\u4e0b useImperativeHandle \u7684\u53c2\u6570\u9879\uff1a<\/p>\n
          useImperativeHandle(ref, createHandle, [deps])<\/code><\/pre>\n