[英]React renders my Component before it actually has Data
所以我很難解決這個問題......通常我只會做一個“ComponentDidMount”但是因為我試圖避免使用類並且只使用反應鈎子我被問題困住了。
我的組件在從 API 獲取任何數據之前呈現,因此我的 .map 函數將無法工作,因為它沒有收到任何數據。
商店.js
import React, { useEffect, useState } from "react";
import { useSelector, useDispatch } from "react-redux";
import { listShops } from "../../Redux/actions/shopActions";
const Shop = () => {
const userShop = useSelector(state => state.shop);
const auth = useSelector(state => state.auth);
const dispatch = useDispatch();
useEffect(() => {
dispatch(listShops(auth));
}, []);
console.log("Look at my userShop",userShop.shop)
return (
<div>
{userShop.map(shop=>(<div>{shop}</div>))}
{console.log("How often do I Render?")}
</div>
);
};
export default Shop;
ShopAction.js
import {GET_SHOPS} from "./types";
export const listShops = userData => async dispatch =>{
const userId = userData.user.id;
await axios.get(`/api/shops/shops/user/${userId}`)
.then(
res => {
const user = res.data;
dispatch({
type: GET_SHOPS,
payload: user.shops
})})
}
shopReducer.js
const initialState = {}
export default function(state = initialState, action) {
switch (action.type) {
case GET_SHOPS:
return {
...state,
shop:action.payload
}
default:
return state;
}
}
if(!userShop){
return <h1>loading<h1>;
}
return (
<div>
{userShop.map(shop=>(<div>{shop}</div>))}
</div>
);
如果state.shop
使用短路評估undefined
則返回一個空數組:
const userShop = useSelector(state => state.shop || []);
return (
<div>
{userShop && userShop.map(shop=>(<div>{shop}</div>))}
</div>
);
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