Mongodb 如何联接Mongoose中的集合并检索特定字段

我在MERN堆栈的Electron 商务平台上工作.在我的项目中，我有三个架构:User、Product和Cart.购物车架构同时引用用户架构和产品架构.

以下是我的简化架构 struct :

CartModel.js

const mongoose = require("mongoose");
const { Schema, model } = mongoose;

const cartSchema = new Schema(
  {
    user: { type: Schema.Types.ObjectId, ref: "User", required: true },
    product: { type: Schema.Types.ObjectId, ref: "Product", required: true },
    unit: { type: Number, required: true },
  },
  { timestamps: true, versionKey: false }
);

const cartModel = model("Cart", cartSchema);
module.exports = cartModel;

ProductModel.js

const mongoose = require("mongoose");
const { Schema, model } = mongoose;

const productSchema = new Schema(
  {
    title: String,
    short_des: String,
    price: Number,
    discount_price: Number,
    image: String,
    stock: String,
    star: String,
  },
  { timestamps: true, versionKey: false }
);

const productModel = model("Product", productSchema);

module.exports = productModel;

UserModel.js

const mongoose = require("mongoose");
const { Schema, model } = mongoose;

const userSchema = new Schema(
  {
    name: { type: String, required: true },
    email: { type: String, unique: true, required: true },
    password: { type: String, required: true },
  },
  { timestamps: true, versionKey: false }
);

const userModel = model("User", userSchema);

module.exports = userModel;

我的问题是，在我的购物车控制器，我试图定义一个查询加入购物车，用户和产品模型，并试图提取特定的信息，但my query isn't working as expected.

我需要提取按用户分组的每个产品的以下信息:

• 购物车对象ID和单位
• 用户名和邮箱
• 产品名称和价格

我try 在数组中返回结果，这样我就可以在我的react前端中使用map方法来显示数据.

CartController.js

exports.cartList = async (req, res) => {
  try {
    let userId = new mongoose.Types.ObjectId(req.user._id);

    let result = await cartModel.aggregate([
      { $match: { user: userId } },
      {
        $lookup: {
          from: "users", // Name of the User model collection
          localField: "user",
          foreignField: "_id",
          as: "userDetails",
        },
      },
      {
        $lookup: {
          from: "products", // Name of the Product model collection
          localField: "product",
          foreignField: "_id",
          as: "productDetails",
        },
      },
      {
        $group: {
          _id: "$user",
        },
      },
    ]);
    res.status(200).json({ status: true, data: result });
  } catch (error) {
    res.status(200).json({ status: false, data: error.message });
  }
};

购物车模型数据示例如下

{
  "_id": {
    "$oid": "6592be024fc8de3f1771a9e1"
  },
  "product": {
    "$oid": "657fab1586f102e3657bf034"
  },
  "user": {
    "$oid": "6559696bfa9b7df357161a81"
  },
  "createdAt": {
    "$date": "2024-01-01T13:28:34.452Z"
  },
  "unit": 4,
  "updatedAt": {
    "$date": "2024-01-01T13:28:46.865Z"
  }
},
{
  "_id": {
    "$oid": "6592dc014fc8de3f1771bc3f"
  },
  "product": {
    "$oid": "65801d5e2c366e8773ada21f"
  },
  "user": {
    "$oid": "6559696bfa9b7df357161a81"
  },
  "createdAt": {
    "$date": "2024-01-01T15:36:33.420Z"
  },
  "unit": 3,
  "updatedAt": {
    "$date": "2024-01-01T15:36:37.161Z"
  }
}

谁可以提供一个聚合查询的指导或示例，该聚合查询以适合在Reaction中映射的格式从多个集合(购物车、用户和产品)中检索指定的信息？如有任何帮助或建议，我们将不胜感激.谢谢!