我正在使用 useEffect 获取 API,并且 API 响应正确,例如
{response: {message: "This is a image link", status: "success"}, error: null}
第二次,当我收到下一个 API 调用响应时,如果出现错误,则旧响应不会被删除。显示是这样的
{response: {message: "This is a image link", status: "success"}, error: TypeError}
我工作this获取API的教程代码
检查我的确切代码代码沙箱
import React, { useState } from "react";
import ReactDOM from "react-dom";
import "./styles.css";
const useFetch = (url, options) => {
console.log("useFetch");
const [response, setResponse] = React.useState(null);
const [error, setError] = React.useState(null);
React.useEffect(() => {
const FetchData = async () => {
try {
const res = await fetch(url, options);
const json = await res.json();
setResponse(json);
// console.log("json - ", json);
} catch (error) {
// console.log("error - ", error);
setError(error);
}
};
FetchData();
}, [url]);
return { response, error };
};
function App() {
const API_URL = `https://dog.ceo/api/breeds/image/random`;
const [apiUrl, setApiUrl] = useState(API_URL);
const res = useFetch(apiUrl, {});
console.log("res - ", res);
if (!res.response) {
return <div>Loading...</div>;
}
const apiCallAgain = () => {
const apiUrl = `https://d.ceo/api/breeds/image/q`;
setApiUrl(apiUrl);
};
const dogName = res.response.status;
const imageUrl = res.response.message;
return (
<div className="App">
<div>
<button onClick={apiCallAgain}>API Call</button>
<h3>{dogName}</h3>
<div>
<img src={imageUrl} alt="avatar" />
</div>
</div>
</div>
);
}
const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);
打开控制台并检查res
默认对象。现在点击API Call
按钮并检查res
再次反对。当我使用 useState 时null
那么为什么在开始时会显示旧状态?