未捕获的类型错误:对象不可迭代 --> 使用带有 Reducer 的上下文
2022-02-01
2014
我正在学习将 useContext 和 useReducer 结合使用,但出现了一个我还没能弄清楚的错误:
Uncaught TypeError: object is not iterable (cannot read property Symbol(Symbol.iterator))
它发生在解构 MealItemForm.js 中的上下文之后。我尝试在 createContext 中设置默认值,使用和不使用花括号导入等等。我试图在子组件内调度该函数。有什么想法吗?
MealItemForm.js
import React,{useContext} from 'react';
import MeatContext from '../store/meat-context';
import Input from './Input';
import styles from "./MealItemForm.module.css"
function MealItemForm(props) {
const [meatState,dispatchMeatState]=useContext(MeatContext)
const handleClick=(event)=>{
event.preventDefault();
}
return (
<form className={styles.form}>
<Input/>
<button onClick={handleClick}>+ Add</button>
</form>
);
}
export default MealItemForm;
meat-context.js
import React,{useReducer,useState} from 'react';
const MeatContext = React.createContext({meatState:[]});
export function MeatContextProvider(props) {
const meatReducer = (state, action) => {
if (action.type === 'ADD_MEAT') {
return [...meatState];
}
return { };
};
const [meatState, dispatchMeatState] = useReducer(meatReducer,
[
]
);
return (
<MeatContext.Provider value={{meatState:meatState,dispatchMeatState:dispatchMeatState}}>
{props.children}
</MeatContext.Provider>
);
}
export default MeatContext
2个回答
提供给
Context
的值是一个对象
{meatState:meatState,dispatchMeatState:dispatchMeatState}
但是您在获取值时使用了数组解构
const [meatState, dispatchMeatState ] = useContext(MeatContext)
使用对象解构应该可以解决这个问题,
const { meatState, dispatchMeatState } = useContext(MeatContext)
Badal Saibo
2022-02-01
用{object}重组,而不是[array]解决问题
Ohiare Nathaniel
2022-09-06