React组件间数据传递：从子组件向父组件通信的最佳实践

// InputField.js
export default function InputField({ onSubmit }) { // 接受 onSubmit prop
  function handleSubmit(e) {
    e.preventDefault(); // 阻止浏览器重新加载页面

    const form = e.target;
    const inputVal = form.myInput.value; // 获取输入框的值

    console.log("Input value from child:", inputVal);

    // 调用父组件传入的回调函数，并将输入值传递给它
    if (onSubmit) {
      onSubmit(inputVal); 
    }
  }

  return (
    <form method="post" onSubmit={handleSubmit}>
      <input name="myInput" id="adress-field" placeholder="Enter address" autoComplete="on" />
      <button type="submit" id="adress-button">Send</button>
    </form>
  );
}

// App.js
import './App.css';
import AccountNumber from "./components/AccountNumber";
import InputField from "./components/InputField";
import { useEffect, useState } from "react";

function App() {
  // 状态用于存储从InputField接收到的搜索值
  const [searchValue, setSearchValue] = useState(''); // 初始化为空字符串，避免首次渲染时请求 'null'

  // token fetch 相关的状态
  const [tokens, setTokens] = useState([]);
  const [loading, setLoading] = useState(false);

  // 定义一个回调函数，用于接收InputField传递过来的值
  const handleSearchSubmit = (val) => {
    setSearchValue(val); // 更新searchValue状态
  };

  // useEffect 钩子用于处理副作用，例如数据获取
  useEffect(() => {
    // 只有当 searchValue 有效时才进行数据请求
    if (searchValue) { 
      setLoading(true);
      fetch(`https://api.multiversx.com/accounts/${searchValue}/tokens`)
        .then(response => response.json())
        .then(json => setTokens(json))
        .catch(error => {
          console.error("Error fetching tokens:", error);
          setTokens([]); // 请求失败时清空或重置tokens
        })
        .finally(() => {
          setLoading(false);
        });
    } else {
      // 如果 searchValue 为空，可以清空tokens或显示提示
      setTokens([]);
      setLoading(false);
    }
    console.log("Current tokens state:", tokens); // 注意：这里可能打印的是旧的tokens状态
  }, [searchValue]); // 依赖数组中包含 searchValue，当其改变时重新运行 effect

  function round(nr, ten) {
    return Math.round(nr * ten) / ten;
  }

  function numberWithSpaces(nr) {
    return nr.toString().replace(/\B(?=(\d{3})+(?!\d))/g, " ");
  }

  return (
    <content className="content">
        <div className="up-side">
            <div className="account-number-box">
                <p id="p-account-number">Total number of accounts</p>
                <p id="account-number"><AccountNumber/></p>
            </div>
            <div className="adress-search">
                {/* 正确地渲染 InputField 组件，并传递回调函数 */}
                <InputField onSubmit={handleSearchSubmit} /> 
            </div>
            {/* 可以显示当前的搜索值以供调试 */}
            <p>Current Search Value: {searchValue}</p>
        </div>
        <div className="down-side">
            <table className="Token-section-output">
              {loading ? (
                <div>Loading...</div>
              ) : (
                <>
                  <h1>Tokens</h1>
                  <table className='Token-section-output' border={0}>
                    <tr className='token-row-type'>
                      <th className='token-column'>Name</th>
                      <th className='center-column'>Price</th>
                      <th>Hold</th>
                    </tr>
                    <tr className="space20"/>

                    {tokens.map(token => (
                      <tr className='token-row' key={token.id}>
                        <td className='token-column'>
                        <img className="img-Tokens" src = {token?.assets?.pngUrl ?? "img/Question.png"} /> 
                          <p>{token.name}</p> 
                        </td>
                        <td className='center-column'> <p>${round(token.price, 10000000)}</p> </td>
                        <td> 
                          <p>{round(token.balance / Math.pow(10, token.decimals), 10000000)}</p> 
                          <p className='token-hold'>${round(token.valueUsd, 10000000)}</p>
                        </td>
                      </tr>
                    ))}
                  </table>
                </>
              )}
            </table>
        </div>   
    </content>
  );
}

export default App;