Mongoose 通过引用字段查找

Question

我有一个这样的频道架构：

const channelSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      unique: true
    }
  }
);

这是反馈模式：

const feedbackSchema = new mongoose.Schema({
  channelId: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "channel",
    require: true
  }
});

如何按频道名称查找反馈？

Feedback.find({channelId.name : 'something'})

谢谢

Answer 1

您无法查询不存在的对象的属性，我建议先查询频道，获取 id 并从那里进行查找。

const channel = await Channel.findOne({ name });
const feedback = await Feedback.find({ channelId: channel._id })

Answer 2

由于您没有从通道架构到反馈架构的任何参考，您可以使用猫鼬的populate-virtuals 功能。

所需的更改如下：

1-) 像这样替换您的频道架构以使用虚拟填充：

const mongoose = require("mongoose");

const channelSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      unique: true
    }
  },
  {
    toJSON: { virtuals: true }
  }
);

// Virtual populate
channelSchema.virtual("feedbacks", {
  ref: "feedback",
  foreignField: "channelId",
  localField: "_id"
});

module.exports = mongoose.model("channel", channelSchema);

2-) 使用以下查询查找给定频道名称的反馈：

请注意，我在查询中对通道名称进行了硬编码，您可以从请求正文或请求查询或请求参数中读取它。

router.get("/feedback", async (req, res) => {
  const result = await Channel.findOne({ name: "Channel 1" }).populate({
    path: "feedbacks"
  });

  res.send(result);
});

响应会是这样的：

[
  {
    "_id": "5de5509476a9c34048c1d23d",
    "name": "Channel 1",
    "__v": 0,
    "feedbacks": [
      {
        "_id": "5de5512d7d87de2d4c6b38d2",
        "channelId": "5de5509476a9c34048c1d23d",
        "__v": 0
      },
      {
        "_id": "5de551357d87de2d4c6b38d3",
        "channelId": "5de5509476a9c34048c1d23d",
        "__v": 0
      }
    ],
    "id": "5de5509476a9c34048c1d23d"
  }
]

或者如果您只对反馈感兴趣，您可以通过result.feedbacks 访问它们：

router.get("/feedback", async (req, res) => {
  const result = await Channel.findOne({ name: "Channel 1" }).populate({
    path: "feedbacks"
  });

  res.send(result.feedbacks);
});

这会给你一系列这样的反馈：

[
    {
        "_id": "5de5512d7d87de2d4c6b38d2",
        "channelId": "5de5509476a9c34048c1d23d",
        "__v": 0
    },
    {
        "_id": "5de551357d87de2d4c6b38d3",
        "channelId": "5de5509476a9c34048c1d23d",
        "__v": 0
    }
]

Answer 3

您可以使用插件mongoose-find-by-reference。

Step.1 安装

npm i -S mongoose-find-by-reference

npm link Github link

Step.2 plugin()插件

const mongoose = require("mongoose");

// Require mongoose-find-by-reference
const { MongooseFindByReference } = require('mongoose-find-by-reference');

await mongoose.connect("mongodb://localhost:27017/test")

const channelSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      unique: true
    }
  }
);


const feedbackSchema = new mongoose.Schema({
  channelId: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "channel",
    require: true
  }
});

// Execute function plugin() on schema with Reference paths
feedbackSchema.plugin(MongooseFindByReference);


const Channel= mongoose.model('channel', channelSchema );
const Feedback= mongoose.model('feedback', feedbackSchema );

Step.3 随便用！

const { _id } = await Channel.create({ name: "C" })

await Feedback.create({channelId : _id})

/** Its conditions will be auto automatically replaced with :
{
  channelId: {
    $in: [
      /* ObjectIDs for Eligible channels */
    ],
  },
}
 */
const findResult = await Feedback.find({channelId.name : 'C'})