javascript - 如何使项目列表在删除项目时自动更新渲染列表？

Question

我正在使用 Redux 构建网络购物车。我的购物车正在运行，除非我删除购物车上的商品时，页面需要刷新或更改才能呈现更改。当项目被删除时如何显示更改？这是我的购物车组件:

import React, { Component } from 'react';
import {addCart} from './Shop';
import { removeCart } from '../../actions'; 
import { connect } from 'react-redux';

export class Cart extends Component {
    constructor(props) {
        super(props);
        this.state = {items: this.props.cart,cart: [],total: 0};
    }

    handleClick(item) {
        this.props.onCartRemove(item);
    } 

    ...
    render() {
        return(
            <div className= "Webcart" id="Webcart">
                <div id='WebcartWrapper'>
                    <ul id='webCartList'>
                        {this.state.items.map((item, index) => {
                            return <li className='cartItems' key={'cartItems_'+index}>
                                <h4>{item.item}</h4>
                                <p>Size: {item.size}</p>
                                <p>Price: {item.price}</p>
                                <button onClick={() => this.handleClick(item)}>Remove</button>
                            </li>
                        })}
                    </ul>
                    <div>Total: ${this.countTotal()}</div>
                </div>
            </div>
        );
    }
}

const mapDispatchToProps = (dispatch) => {
    return {
        onCartAdd: (cart) => {
            dispatch(addCart(cart));
        },
        onCartRemove: (item) => {
            dispatch(removeCart(item));
        },
    }
}

function mapStateToProps(state) {
  return { cart: state.cart };
}

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

这些是我的操作:

export const ADD_CART = 'ADD_CART';
export const REMOVE_CART = 'REMOVE_CART';

export function addCart(item){
    return {
        type: ADD_CART,
        payload: item
    }
};

export function removeCart(item){
    return{
        type:REMOVE_CART,
        payload: item
    }
};

这些是我的 reducer :

import {ADD_CART} from './actions';
import {REMOVE_CART} from './actions';
import { REHYDRATE } from 'redux-persist/constants';

export default Reducer;

var initialState = {
  cart:{},
  data: [],
  url: "/api/comments",
  pollInterval: 2000
};

function Reducer(state = initialState, action){
    switch(action.type){
        case REHYDRATE:
                if (action.payload && action.payload.cart) {
                    return { ...state, ...action.payload.cart };
                }
            return state;

            case ADD_CART:
                return {
                    ...state,
                    cart: [...state.cart, action.payload]
                }

            case REMOVE_CART:
                return {
                    ...state,
                    cart: state.cart.filter((item) => action.payload !== item)
                }



            default:
                return state; 
    };
}

如果需要更多我的代码，请询问。如何让网络购物车列表在删除商品时自动更新？

Answer 1

您需要更新您的状态以使其再次渲染..

在购物车组件中，只需添加功能

...
componentWillReceiveProps(nextprops)
{
 this.setState({
  items: nextprops.cart
 })
}
...

*) componentWillReceiveProps 会在handleClick中的execdispatch()之后调用，将reducers中的新闻数据返回到cart组件的this.props中。

在您的代码中例如:

export class Cart extends Component {
    constructor(props) {
        ...
    }

    componentWillReceiveProps(nextprops)
    {
     this.setState({
      items: nextprops.cart
     })
    }

    handleClick(item) {
        ...
    } 

    render() {
    ...
    }
}