在React-Redux中计算小计

Question

我建立了一个商店，并试图找到在UI上显示SubTotal的正确方法…我的代码"Cart"我想放置计算SubTotal函数的位置如下:

import React, { Component } from "react"
import { Card, CardBody, CardHeader, CardTitle, Row, Col } from "reactstrap"
import PanelHeader from "components/PanelHeader/PanelHeader.js"
import { connect } from "react-redux";
import { removeCart} from "../redux/actions";

class Cart extends Component {
removeFromCart = (product) => {
const cartProducts = this.props.cart 
const updatedCartProducts = cartProducts.filter(item => item.id !== product.id);

}

render () {
const cartProducts = this.props.cart
const subtotal = (cartProducts.quantity * cartProducts.price).toFixed(2);

return (
<>
<PanelHeader size="sm" />
<div className="content">
<Row>
<Col xs={12}>
<Card>
<CardHeader>
<CardTitle tag="h4">Products List</CardTitle>
</CardHeader>
<CardBody>
<table class="table table-striped table-hover">
<thead>
<tr>
<th scope="col"><strong>#</strong></th>
<th scope="col"><strong>Name</strong></th>
<th scope="col"><strong>Code Item</strong></th>
<th scope="col"><strong>Quantity</strong></th>
<th scope="col"><strong>Price</strong></th>
<th scope="col"><strong>Sub Total</strong></th>

</tr>
</thead>
<tbody>
{cartProducts.map((cartProduct, index) => (             
<tr key={cartProduct.id}>
<th scope="row">{index +1}</th>
<td>{cartProduct.title}</td>
<td>{cartProduct.code}</td>
<td>{cartProduct.quantity}</td>
<td>{cartProduct.price}</td>
<td>{subtotal}</td>
<td><button onClick ={() => this.props.removeCart(cartProduct)} className="btn btn-danger cart-button px-4">Remove</button></td>
</tr>))}
</tbody>
</table>
</CardBody>
</Card>
</Col>
</Row>
</div>
</>
)
}
}

const mapStateToProps = (state)=> {
return {
cart: state.cart
}
}
const mapDispatchToProps = (dispatch) => { 
return {
removeCart: (product) => {dispatch(removeCart(product))}
}
}
export default connect(mapStateToProps, mapDispatchToProps)(Cart);

和我的redux文件，其中addToCart和removeFromCart是如下:

import { ADD_TO_CART } from './constants'
import { REMOVE_FROM_CART } from './constants'
// import { ADD_QUANTITY} from './constants'
// import { SUB_QUANTITY}  from './constants'
// import { EMPTY_CART}  from './constants'

const initialState = {
cart: [],
}
const ShoppinReducer = (state = initialState, action) => {
switch (action.type) {
case ADD_TO_CART:
let newCart = [...state.cart]
let itemIndex = state.cart.findIndex(obj => obj.id === action.payload.id)
let currItem = state.cart[itemIndex]
if (currItem) {
currItem.quantity = parseInt(currItem.quantity) + 1
state.cart[itemIndex] = currItem
newCart = [...state.cart]
}
else {
newCart = newCart.concat(action.payload)
}
return {
cart: newCart
}
case REMOVE_FROM_CART:
const cart = [...state.cart]
const updatedCart = cart.filter(item => item.id !== action.payload.id)
return {
...state,
cart: updatedCart
}

default:
return state
}
}
export default ShoppinReducer

我知道最好不要使用redux来实现SubTotal，但是我发布了它以征求任何建议!请记住代码:

const subtotal = (cartProducts.quantity * cartProducts.price).toFixed(2);

不工作，所以我正试图找到另一种方法!谢谢你的帮助!

Answer 1

我发现了什么是错误的，我更新了我的问题的答案，以供将来参考:

语法非常简单:

<td>{cartProduct.price * cartProduct.quantity}</td>

然而，这段代码在我的UI上收到NaN。所以，我必须改变我的对象数组。我在CartProduct price前面有一个$符号，所以每次我点击addToCart这个NaN时都会返回给我。通过从CartProducts中删除$符号，我上面发布的代码工作得很好!