如何从一个组件导入一个函数对另一个组件做出反应以呈现它？

Question

我正在使用钩子在 react 中进行我的第一个测试。 我创建了一个“地理”组件来在屏幕上显示坐标

import React, { useEffect, useState } from 'react';


function useCoordinates() {
    const [coordinates, setCoordinates] = useState({
        latitude: null,
        longitude: null
    });
    let geoId;

    useEffect(() => {
        geoId = window.navigator.geolocation.watchPosition(position => {
            setCoordinates({
                latitude: position.coords.latitude,
                longitude: position.coords.longitude
            });
        });
        return () => {
            navigator.geolocation.clearWatch(geoId);
        };
    });

    return coordinates;
}

export default function coordinates() {
    const coordinates = useCoordinates();

    return coordinates.latitude == null ? (
        <div>Loading ...</div>
    ) : (
        <div>
            <h2>Latitude: {coordinates.latitude}</h2>
            <h2>Longitude: {coordinates.longitude}</h2>
        </div>
    )
}

现在我正在尝试将它导入到我的“应用程序”组件中以呈现它。 我已经导入了组件和函数，并在“应用程序”组件的“渲染”中调用它，这是我想要显示它的地方。

import React, { useState } from "react";
import "./App.css";
import { sum } from "./lib/math";
import geo, { coordinates } from './components/geo';

function App() {
  const [param1, setParam1] = useState(0);
  const [param2, setParam2] = useState(0);
  const [result, setResult] = useState(0);

  const handleSum = () => {
    setResult(sum(param1, param2));
    setParam1(0);
    setParam2(0);
  };

  const [count, setCount] = useState(0);

  return (
    <div className="App">
      <div>
        <input
          id="param1"
          type="number"
          value={param1}
          onChange={(e) => setParam1(e.target.value)}
        />

        <input
          id="param2"
          type="number"
          value={param2}
          onChange={(e) => setParam2(e.target.value)}
        />

        <button id="sum" onClick={handleSum}>
          Sumar
        </button>

        <p id="result">{result}</p>
      </div>
      <div>
        Count is: {count}
        <button onClick={() => setCount(count + 1)}>Increase</button>
      </div>
      <coordinates />
    </div>
  );
}

export default App;

控制台返回以下错误“在既不是 React 函数组件也不是自定义 React Hook 函数的函数“坐标”中调用了 React Hook“useCoordinates”。

我究竟做错了什么？ 我应该如何导入它？

Answer 1

导入语句不正确，您也没有导出 customHook。

export function useCoordinates() { // maybe export this if you want to use this else where
    const [coordinates, setCoordinates] = useState({
        latitude: null,
        longitude: null
    });
    let geoId;

    useEffect(() => {
        geoId = window.navigator.geolocation.watchPosition(position => {
            setCoordinates({
                latitude: position.coords.latitude,
                longitude: position.coords.longitude
            });
        });
        return () => {
            navigator.geolocation.clearWatch(geoId);
        };
    });

    return coordinates;
}

export default function Coordinates() { // Pascal case is best for components
    const coordinates = useCoordinates();

    return coordinates.latitude == null ? (
        <div>Loading ...</div>
    ) : (
        <div>
            <h2>Latitude: {coordinates.latitude}</h2>
            <h2>Longitude: {coordinates.longitude}</h2>
        </div>
    )
}

假设您只想导入组件，导入应该是这样的：

import Coordinates from './components/geo';

用它作为

<Coordinates/>