我如何防止我的产品列表在父组件购物车状态更新时重新呈现？

Question

我有一个 Main.js 组件，路由到各种组件，包括 Listing.js.

Main：它包含添加到购物车的产品数组作为状态。
List：商品的listing。它包含数据库中所有产品的状态。

我的问题： 当我通过单击列表组件中的按钮将产品添加到购物车时，它会将产品添加到购物车，更新状态 [=38= Main 组件的 ]cart。这样做时，List 组件重新呈现，并且我松开了访问者在列表中设置的所有过滤器。

我想阻止 List 在其父组件的购物车状态发生变化时重新呈现。你知道怎么做吗？我试过 shouldComponentUpdate，但没有成功。

Main.js（父组件）

import React from 'react';
import {Switch, Route, withRouter, Link} from "react-router-dom";
import {List} from "./Listing/List";

class Main extends React.Component
{
    state={
        cart:[],
    };

    removeFromCart = product => //REMOVES PRODUCT FROM CART
    {
        let cart = this.state.cart;
        cart.map(item => {
            if(item._id === product._id)
            {
                item.count--;
                return item;
            }
        });
        cart = cart.filter(item => item.count > 0);
        this.setState({cart:cart}, () => {sessionStorage.setItem('cart', JSON.stringify(cart));});
    };

    addToCart = product => //ADD PRODUCT TO CART
    {
        let cart = this.state.cart;
        let productExists = this.state.cart.map(item => {return item._id === product._id}).includes(true);

        if(productExists)
        {
            cart = cart.map(item => {
                if(item._id === product._id)
                {
                    item.count++;
                    return item;
                }
                else
                {
                    return item;
                }
            });
        }
        else
        {
            product.count = 1;
            cart.push(product);
        }

        this.setState({cart: cart}, () => {sessionStorage.setItem('cart', JSON.stringify(cart));});
    };

    componentWillMount()
    {
        if(sessionStorage.getItem('cart')) this.setState({cart:JSON.parse(sessionStorage.getItem('cart'))});
    }

    render() {
        return (
            <div className='main'>
                <Header cart={this.state.cart} />
                <Switch>
                    <Route path='/listing' component={() => <List addToCart={this.addToCart} />} />
                </Switch>
            </div>
        );
    }
}

export default withRouter(Main);

List.js，产品列表：

import React from "react";
import {Product} from "./Product";
import Data from '../../Utils/Data';
import {Search} from "./Search/Search";

export class List extends React.Component
{

    state = {
        serie: '',
        products: [],
        filteredProducts: [],
    };

    addToCart = this.props.addToCart;

    obtainProducts = (request = {}) => //searches for products in database
    {
        Data.products.obtain(request).then(products => {
            this.setState({products:products, filteredProducts: products});
        });
    };

    displayProducts = () => {
        //Only products that has title
        const products = this.state.filteredProducts.filter(product => {return product.title;});

        //Returns REACT COMPONENT
        return products.map(product => {
            return <Product
                key={product._id}
                product={product}
                addToCart={this.addToCart}
            />
        });
    };

    searchHandler = (collection, types) =>
    {

        let filteredProducts = this.state.products;
        if(collection.length)
            filteredProducts = filteredProducts.filter(product => {return collection.includes(product.series);});
        if(types.length)
            filteredProducts = filteredProducts.filter(product => {return types.includes(product.type);});

        this.setState({filteredProducts: filteredProducts});
    };

    componentWillMount()
    {
        //init products collection
        this.obtainProducts();
    }

    render()
    {
        const productComponents = this.displayProducts();
        console.log('test');
        return(
            <section className='listing'>
                <Search searchHandler={this.searchHandler} />
                <div className='listing-content grid-4 has-gutter'>
                    {productComponents}
                </div>
            </section>
        )
    }
}

Answer 1

如果您将匿名函数传递给路由中的 component 属性，它每次都会重新呈现。相反，将您的路线设置为：

<Route path='/listing' render={() => <List addToCart={this.addToCart} />} />

引用自反应路由器 docs:

When you use component (instead of render or children, below) the router uses React.createElement to create a new React element from the given component. That means if you provide an inline function to the component prop, you would create a new component every render. This results in the existing component unmounting and the new component mounting instead of just updating the existing component. When using an inline function for inline rendering, use the render or the children prop

Answer 2

在 React 的匿名函数中包装元素将导致该元素在每次渲染时重新实例化（在某些情况下）。

我认为问题在于您如何使用 Route 组件。使用 children 道具可能会使这更直观。

<Route path='/listing'>
 <List addToCart={this.addToCart} />
</Route>

我如何防止我的产品列表在父组件购物车状态更新时重新呈现？

How could I prevent my product list to rerender while parent component cart state updates?

javascript

reactjs

components

react-component

react-state-management