[英]How to update an array using useState Hook
我試圖從 URL 獲取數據並將結果作為 JSON 格式,然后在我的狀態中不存儲對象結果。 但它總是返回一個空數組。
const [genres, setGenres] = useState([]);
useEffect(() => {
const getGenres = async () => {
fetch("https://quote-garden.herokuapp.com/api/v2/genres")
.then((response) => response.json())
.then((data) => {
for (const g of data.genres) {
setGenres((oldGenres) => [...oldGenres, g]);
}
});
};
getGenres();
}, []);
這是代碼:我看不出問題出在哪里。 ps:我刪除了導入所以代碼更具可讀性
import React, { useEffect, useState } from "react";
function App() {
const [quoteOfTheDay, setQuoteOfTheDay] = useState("");
const [authorOfQod, setAuthorOfQod] = useState("");
useEffect(() => {
const getQuoteOfTheDay = async () => {
fetch("https://quotes.rest/qod?language=en")
.then((response) => response.json())
.then((data) => {
const qod = data.contents.quotes[0].quote;
const author = data.contents.quotes[0].author;
setQuoteOfTheDay(qod);
setAuthorOfQod(author);
});
};
getQuoteOfTheDay();
}, []);
const [genres, setGenres] = useState([]);
useEffect(() => {
const getGenres = async () => {
fetch("https://quote-garden.herokuapp.com/api/v2/genres")
.then((response) => response.json())
.then((data) => {
for (const g of data.genres) {
setGenres((oldGenres) => [...oldGenres, g]);
}
});
console.log(genres); // genres always empty
};
getGenres();
}, []);
return (
<div className="app">
<Head quoteOfTheDay={quoteOfTheDay} author={authorOfQod} />
<div className="app__category">
<QuoteCategory genre="sport" />
</div>
</div>
);
}
export default App;
非常感謝
我認為如果你改變它應該有效
for (const g of data.genres) {
setGenres((oldGenres) => [...oldGenres, g]);
}
到
setGenres((oldGenres) => [...oldGenres, ...data.genres]);
你確定嗎
useEffect(() => {
const getGenres = async () => {
fetch("https://quote-garden.herokuapp.com/api/v2/genres")
.then((response) => response.json())
.then((data) => {
setGenres(data.genres);
});
};
getGenres();
}, []);
是不足夠的? :)
向上。 如果你開始了,你可以使用async-await
語法直到結束。 它看起來更整潔。
useEffect(() => {
const getGenres = async () => {
const response = await fetch("https://quote-garden.herokuapp.com/api/v2/genres");
const { genres } = await response.json();
setGenres(genres);
};
getGenres();
}, []);
你應該把genresState
作為你的依賴
const [genresState, setGenres] = useState([])
useEffect(() => {
const getGenres = async () => {
const response = await fetch("https://quote-garden.herokuapp.com/api/v2/genres");
const { genres } = await response.json();
setGenres(genres);
};
getGenres();
}, [genresState]);
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