当张贴到数据库时，I'我得到了一个“;可以't在它们被发送错误之后设置报头”;

在这个问题中，我发布了从开始到结束的完整销售数据流，因为我不知道错误在哪里。在我的应用程序中，我在Checkout组件中调用一个名为handlePay（）的函数，该函数反过来调用一个称为makeSale（）的操作创建者。makeSale（）然后在router.js中向服务器发出POST请求，服务器将使用mongose在数据库中处理此销售。控制台的错误读取

"/Users/marcushurney/Desktop/p.O.S/nod_module/mongodb/lib/utils.js:98process.nextTick（function（）｛throw-err；｝）；^

错误：发送邮件头后无法设置邮件头。"

我不确定与router.js或前端其他地方的数据库通信的代码中是否存在此错误。前端的组件名为Checkout.jsx，处理销售的函数是handlePay（），其关联的操作创建者是makeSale（）。

Checkout.jsx

handlePay: function() {
        var props = {
            user_id: this.props.activeUser._id, //This sale will belong to the user that is logged in (global state)
            items: [], //All the items in the cart will be added to the sale below (global state)
            total: this.props.cartTotal //Total price of the sale is drawn from the global state
        }

        this.props.cart.map((product) => {
            var item = {};
            item.name = product.name;
            item.product_id = product._id;
            item.cartQuantity = product.cartQuantity;
            item.priceValue = product.price;
            props.items.push(item);
        });
        var jsonProps = JSON.stringify(props); //converts properties into json before sending them to the server
        this.props.makeSale(jsonProps); 
    }

actions/index.js

export function makeSale(props) {
    var config = {headers: {'authorization' : localStorage.getItem('token')}};
    var request = axios.post('/makeSale', props, config); //This will store the sale in the database and also return it
    return {
        type: MAKE_SALE,
        payload: request //Sends sale along to be used in sale_reducer.js
    };
}

router.js

    //Adds a new sale to the database
    //Getting error "can't set headers after they are sent"
    app.post('/makeSale', function(req, res, next){
        var sale = new Sale();
        sale.owner = req.body.user_id;
        sale.total = req.body.total;
        req.body.items.map((item)=> {
            //pushs an item from the request object into the items array           contained in the sale document
            sale.items.push({
                item: item.product_id,
                itemName: item.name,
                cartQuantity: parseInt(item.cartQuantity), //adds cartQuantity to sale
                price: parseFloat(item.priceValue)
            });

            Product.findById(item.product_id)
            .then((product) => {
                //finds the item to be sold in the database and updates its quantity field based on the quantity being sold
                product.quantity -= item.cartQuantity; 
                //resets the product's cartQuantity to 1
                product.cartQuantity = 1;
                product.save(function(err) {
                    if (err) { 
                        return next(err); 
                    } else {
                        return next();
                        // return res.status(200).json(product);
                    }
                });
            }, (error) => {
              return next(error);
            });
        });
        //gives the sale a date field equal to current date
        sale.date = new Date();
        //saves and returns the sale
        sale.save(function(err) {
            if (err) { return next(err); }
            return res.status(200).json(sale); //Returns the sale so that it can be used in the sale_reducer.js
        });
    });

这是猫鼬-->sale.js的销售模型

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var SalesSchema = new Schema({
    owner: { type: Schema.Types.ObjectId, ref: 'User'},
    total: { type: Number, default: 0},
    items: [{
        item: { type: Schema.Types.ObjectId, ref: 'Product'},
        itemName: { type: String, default: "no name provided"},
        cartQuantity: { type: Number, default: 1 },
        price: { type: Number, default: 0 }
    }],
    date: Date
});
module.exports = mongoose.model('Sale', SalesSchema);