[英]Cannot read property 'type' of undefined in Redux
我正在編寫反應功能組件,它應該從服務器獲取一些數據。 我正在使用 redux,但出現錯誤“無法讀取未定義的屬性‘類型’”
幫助我,請找出我的錯誤
這是我的反應組件 Products.js。 我認為導出部分可能存在錯誤。 父組件 Products.js (App.js) 也包裹在 Provider 上
import React, { useState, useEffect } from 'react';
import { connect } from 'react-redux';
import { fetchProducts } from '../actions/productActions';
import { productsReducer } from '../reducers/productReducers'
function Products({ store, products, cartItems, setCartItems }) {
useEffect(() => {
store.dispatch(productsReducer())
})
const [product, setProduct] = useState(null);
return (
<div>
{
!products
? (<div>Loading...</div>)
:
(<ul className="products">
{products.map(product => (
<li key={product._id}>
<div className="product">
<a href={"#" + product._id}>
<img src={product.image} alt={product.title} />
<p>{product.title}</p>
</a>
<div className="product-price">
<div>${product.price}</div>
<button>Add To Cart</button>
</div>
</div>
</li>
))}
</ul>)
}
</div >
)
}
export default connect((state) => ({ products: state.products.items }), {
fetchProducts,
})(Products);
這是我的 store.js
import { createStore, applyMiddleware, compose, combineReducers } from 'redux';
import thunk from 'redux-thunk';
import { productsReducer } from './reducers/productReducers';
const initialState = {};
const composeEnhancer = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ || compose;
const store = createStore(
combineReducers({
products: productsReducer,
}),
initialState,
composeEnhancer(applyMiddleware(thunk))
)
export default store;
我的減速器,我在這個文件中遇到錯誤(無法讀取未定義的屬性“類型”),也許,我在傳輸錯誤“操作”
import { FETCH_PRODUCTS } from "../types";
export const productsReducer = (state = {}, action) => {
switch (action.type) {
case FETCH_PRODUCTS:
console.log('it work!')
return { items: action.payload };
default:
return state;
}
};
我的行動
import { FETCH_PRODUCTS } from "../types";
export const fetchProducts = () => async (dispatch) => {
const res = await fetch("/api/products");
const data = await res.json();
console.log(data);
dispatch({
type: FETCH_PRODUCTS,
payload: data,
});
};
和我的類型
export const FETCH_PRODUCTS = "FETCH_PRODUCTS"
這是關於 redux 的研究項目,但在 class 組件上的原始教師編寫代碼中。 原始代碼在這里和這里
如果我像源代碼一樣編寫 class 組件,一切正常,所以我認為這是錯誤的原因
dispatch
function 期望 redux 動作作為參數,而不是減速器。 在你的情況下:
import { fetchProducts } from '../actions/productActions';
function Products({ store, products, cartItems, setCartItems }) {
useEffect(() => {
store.dispatch(fetchProducts());
})
...
}
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