React Native Redux 购物车应用问题

分类：编程问答

如何解决React Native Redux 购物车应用问题

我正在尝试制作一个应用程序，允许用户在我的 DetailsComponent.js 页面中选择“添加到购物车”。我目前正在更新我的商店中名为“cart”的数组，其 ID 对应于商店内产品数组中的产品。我已经检查了调试器，并且产品 ID 已正确添加到购物车数组中。 我正在使用以下代码在我的购物车页面上显示与我的购物车中的产品 ID 匹配的产品，但我的购物车目前没有显示任何内容。

CartComponent.js

import React,{ Component } from 'react';
import { FlatList,View,Text,Alert } from 'react-native';
import { ListItem } from 'react-native-elements';
import { connect } from 'react-redux';
import { baseUrl } from '../shared/baseUrl';
import { Loading } from './LoadingComponent';
import { removeCart } from '../redux/ActionCreators';


const mapStateToProps = state => {
    return {
        products: state.products,cart: state.cart
    }
}

const mapDispatchToProps =  dispatch => ({
    removeCart: (id) => dispatch(removeCart(id))
});

class CartScreen extends Component {
    
    render() {

        const renderMenuItem = ({item,index}) => {
            return(
               <ListItem 
                    key={index}    
                    bottomDivider
                >
                   <ListItem.Content>
                        <ListItem.Title>
                            {item.name}
                        </ListItem.Title>
                        <ListItem.Subtitle>
                            {item.quantity} chargers: ${item.price}
                        </ListItem.Subtitle>
                   </ListItem.Content>
                   
               </ListItem>
            );
        }
        if (this.props.cart.isLoading) {
            return(
                <Loading />
            )
        }
        else if (this.props.cart.errMess) {
            return(
                <Text>{this.props.cart.errMess}</Text>
            )
        }
        else {
            return(
            <View>
                <Text>
                    Cart
                </Text>
                <FlatList
                    data={this.props.products.products.filter(product => this.props.cart.cart.some(el => el === product.id))}
                    renderItem={renderMenuItem}
                    keyExtractor={item => item.id.toString()}
                />
            </View>
            );
        }
    }
}
export default connect(mapStateToProps,mapDispatchToProps)(CartScreen);

我已经包含了我的其他文件以获取更多信息。

我有不同的 DropDownPicker 值对应于我的 redux 商店中的产品 ID。商店中的这些商品具有要在 CartComponent.js 中使用的数量和价格值。

DetailsComponent.js

import React,{ Component } from 'react';
import { Text,Image,Button,FlatList,StyleSheet,ScrollView} from 'react-native';
import DropDownPicker from 'react-native-dropdown-picker';
import { baseUrl } from '../shared/baseUrl';
import { connect } from 'react-redux';
import { Loading } from './LoadingComponent';
import { postCart } from '../redux/ActionCreators';


const mapStateToProps = state => {
    return{
        chargers: state.chargers,utensils: state.utensils,orders: state.orders,products: state.products
    }
}

const mapDispatchToProps = dispatch => ({
    postCart: (id) => dispatch(postCart(id))
})

class DetailsScreen extends Component {
    constructor(props) {
        super();
        this.state = {
            itemId: '',orderAmount: '',orderPrice: ''
        }
    }

    addToCart(id) {
        this.props.postCart(id);
    }

    render() {
        const categoryName = this.props.route.params.categoryName;
        const productId = this.props.route.params.menuId;                  
        const item = this.props[categoryName][categoryName][productId];
        if (categoryName === "chargers") {
            if (productId === 0) {
                var amounts = [
                    {label: '50',value: '1'},{label: '100',value: '2'},{label: '150',value: '3'},{label: '200',value: '4'},{label: '250',value: '5'},{label: '300',value: '6'},{label: '350',value: '7'},{label: '400',value: '8'},{label: '450',value: '9'},{label: '500',value: '10'},{label: '550',value: '11'},{label: '600',value: '12'},];
            }
            else if (productId === 1) {
                var amounts = [
                    {label: '50',value: '14'},value: '15'},value: '16'},value: '17'},value: '18'},value: '19'},value: '20'},value: '21'},value: '22'},value: '23'},value: '24'},value: '25'},];
            }
            else if (productId === 2) {
                var amounts = [
                    {label: '50',value: '27'},value: '28'},value: '29'},value: '30'},value: '31'},value: '32'},value: '33'},value: '34'},value: '35'},value: '36'},value: '37'},value: '38'},];
            }
        }
        else if (categoryName === "utensils") {
            if (productId === 0) {
                var amounts = [
                    {label: '1',value: '40'},{label: '2',value: '41'},{label: '3',value: '42'},{label: '4',value: '43'},{label: '5',value: '44'},];
            }
            else if (productId === 1) {
                var amounts = [
                    {label: '1',value: '46'},value: '47'},value: '48'},value: '49'},value: '50'},];
            }
                
        }
        
        
        if (this.props[categoryName].isLoading) {
            return(
                <Loading />
            )
        }
        else if (this.props[categoryName].errMess) {
            return(
                <Text>
                    {this.props[categoryName][categoryName].errMess}
                </Text>
            )
        }
        else {
            return(
                <ScrollView>
                    <Text style={styles.title}>
                        {item.name}
                    </Text>
                    <Text>
                        {item.category}
                    </Text>
                    <View style={{flex: 1,flexDirection: 'row'}}>
                        <Image
                            style={styles.image}
                            source={{uri: baseUrl + item.image}}
                        />
                        <DropDownPicker
                            items={amounts}
                            defaultNull
                            placeholder="Select amount"
                            containerStyle={{height: 40,width: 100}}
                            itemStyle={{
                                justifyContent: 'flex-start'
                            }}
                            onChangeItem={item => this.setState({
                                itemId: this.props.products.products[item.value].id,orderAmount: this.props.products.products[item.value].quantity,orderPrice: this.props.products.products[item.value].price
                            })}
                        />
                    </View>
                    
                    <Text>
                        {item.description}
                    </Text>
                    
                    <Text>
                        Your order is {this.state.orderAmount} {this.props[categoryName][categoryName][productId].name} chargers for ${this.state.orderPrice}
                    </Text>
                    <Button
                        title='Add to Cart'
                        color="#f194ff"
                        onPress={() => this.addToCart(this.state.itemId)}
                    />
    
                </ScrollView>
            )
        }
        
    }
}

const styles = StyleSheet.create({
    container: {
      flex: 1,},image: {
        resizeMode: "contain",height: 200,width: 200
    },title: {
      fontSize: 32,});

export default connect(mapStateToProps,mapDispatchToProps)(DetailsScreen);

以下代码示例是我的 redux 文件。为了便于阅读，我仅使用购物车信息对其进行了简化。

ActionCreators.js

export const fetchCart = () => (dispatch) => {
    
    dispatch(cartLoading());

    return fetch(baseUrl + 'cart')
    .then(response => {
        if (response.ok) {
            return response;
        } else {
            var error = new Error('Error ' + response.status + ': ' + response.statusText);
            error.response = response;
            throw error;
        }
        },error => {
            var errmess = new Error(error.message);
            throw errmess;
        })
    .then(response => response.json())
    .then(cart => dispatch(addCart(cart)))
    .catch(error => dispatch(cartFailed(error.message)));
};

export const cartLoading = () => ({
    type: ActionTypes.CART_LOADING
});

export const cartFailed = (errmess) => ({
    type: ActionTypes.CART_FAILED,payload: errmess
});

export const postCart = (id) => (dispatch) => {
    const newCart = {
        id: id
    };
    setTimeout(() => {
        dispatch(addToCart(newCart));
    },2000);
};

export const addToCart = (cart) => ({
    type: ActionTypes.ADD_TO_CART,payload: cart
});

export const addCart = (id) => ({
    type: ActionTypes.ADD_CART,payload: id
});

export const removeCart = (id) => ({
    type: ActionTypes.REMOVE_CART,payload: id
});

ActionTypes.js

export const POST_CART = 'POST_CART';
export const ADD_TO_CART = 'ADD_TO_CART';
export const ADD_CART = 'ADD_CART';
export const REMOVE_CART = 'REMOVE_CART';
export const CART_LOADING = 'CART_LOADING';
export const CART_FAILED = 'CART_FAILED';

cart.js

import * as ActionTypes from './ActionTypes';

export const cart = (
    state = { 
        isLoading: true,errMess: null,cart:[]
    },action) => {
        switch (action.type) {
            case ActionTypes.ADD_CART:
                return {...state,isLoading: false,cart: action.payload};
    
            case ActionTypes.CART_LOADING:
                return {...state,isLoading: true,cart: []};
    
            case ActionTypes.CART_FAILED:
                return {...state,errMess: action.payload};

            case ActionTypes.ADD_TO_CART:
                var newCart = action.payload;
                return {...state,cart: state.cart.concat(newCart) };
    
            default:
                return state;
        }
    };

以下是我的 db.json 文件。我已将一项项目输入到购物车数组中进行测试，但它也没有显示在购物车中。还简化了此文件以仅显示少数产品以提高可读性。

"products": [
        {
            "id": 0,"name": "Ezywhip Pro","category": "chargers","label": "","featured": false,"description": "Ezywhip Pro Cream Chargers,Made by MOSA","image": "images/ezywhip.png","quantity": 0,"price": 0
        },{
            "id": 1,"category": "ezy","quantity": 50,"price": 40
        },{
            "id": 2,"quantity": 100,"price": 70
        },{
            "id": 3,"quantity": 150,"price": 110
        }
    ],"cart": [
        {
            "id": 1
        }
    ]
}

如果有人能解释我做错了什么，将不胜感激。

解决方法

我通过更改以下内容使其工作：

export const addToCart = (id) => ({
    type: ActionTypes.ADD_TO_CART,payload: id
});

不确定这是否会导致任何问题，但为了安全起见，我将其更改为 id。

这就是导致主要问题的原因，我需要使用 el.id 来指定我在数据中与之比较的内容。

<FlatList
  data={this.props.products.products.filter(product => this.props.carts.carts.some(el => el.id === product.id))}
  renderItem={renderMenuItem}
  keyExtractor={item => item.id.toString()}
/>

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