使用数组内的模式流行模式的字段（猫鼬）答案

【问题标题】：Popular a field of a schema with a schema that is inside an array (Moongose)使用数组内的模式流行模式的字段（猫鼬）
【发布时间】：2021-02-16 17:38:36
【问题描述】：

我需要获取指向city_id的数据，它是一个Schema，它链接到另一个Schema的数组。

This is the Schema called Companies and I need to get information about the city

{
"_id": "5fa1484a34a032ac5687b1c2",
"name": "Company",
"address": "Address",
"email": "email@email.com",
"phone": 123456789,
"city_id": "5fa147b607f466ac1d536bd0",
"__v": 0

现在，这是城市模式。我有一个位置架构，其中包含一个国家关系：

import Country from './countrySchema';
const locationSchema = new Schema({
    region: {
       type: String,
       required: true,
       unique: true,
       dropDups: true
    },
    locations: [Country.schema]
},{ timestamps: true});

const locationModel = model("Location", locationSchema);

这是 Country Schema，其中包含 City 关系：

import City from './CitySchema';
const countrySchema = new Schema({
    country_name: {
        type: String,
        required: true,
        unique: true,
        dropDups: true
    },
    cities: [City.schema]
},{ _id: true, timestamps: true });

const countryModel = model("Country", countrySchema);

这是城市架构：

const citySchema = new Schema({
    city_name: {
        type: String,
        required: true,
        unique: true,
        dropDups: true
    }
},{ _id: true, timestamps: true });

const cityModel = model("City", citySchema);

最后，这看起来像：

"_id": "5fa147b607f466ac1d536bce",
  "locations": [
    {
      "_id": "5fa147b607f466ac1d536bcf",
      "country_name": "Colombia",
      "cities": [
        {
          "_id": "5fa147b607f466ac1d536bd0",
          "city_name": "Medellín",
          "createdAt": "2020-11-03T12:06:14.914Z",
          "updatedAt": "2020-11-03T12:06:14.914Z"
        },
        {
          "_id": "5fa147b607f466ac1d536bd1",
          "city_name": "Bogotá",
          "createdAt": "2020-11-03T12:06:14.914Z",
          "updatedAt": "2020-11-03T12:06:14.914Z"
        }
      ],
      "createdAt": "2020-11-03T12:06:14.914Z",
      "updatedAt": "2020-11-03T12:06:14.914Z"
    },

如何获取城市信息？非常感谢。

【问题讨论】：

标签： arrays mongodb mongoose mongodb-query

【解决方案1】：

试试这个：

 locationModel.findOne({_id:"5fa147b607f466ac1d536bce"})
      .populate({ path:"locations",{path:"cities"}})
      .exec((err,location) => {
               if(err) reject(err);
               return resolve(location);   
            })`

【讨论】：