猫鼬虚拟填充无限循环

Question

我正在尝试使用与之相关的教程来填充标签，当我在查询中使用.populate（）时，它可以工作，但是当我直接在模型上进行操作时，我会有一个inifite循环。

这是我的代码：

Tag.js

const mongoose = require("mongoose");

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

tagSchema.virtual("tutorials", {
  ref: "Tutorial",
  foreignField: "tags",
  localField: "_id"
});

tagSchema.pre(/^find/, function(next) {
  // That's the code that causes an infinite loop
  this.populate({
    path: "tutorials",
    select: "-__v"
  });

  next();
});

const Tag = mongoose.model("Tag", tagSchema);

module.exports = Tag;

Tutorial.js

const mongoose = require('mongoose');

const tutorialSchema = new mongoose.Schema({
  title: {
    type: String,
    required: true,
    unique: true,
    trim: true
  },
  tags: {
    type: [
      {
        type: mongoose.Schema.ObjectId,
        ref: 'Tag'
      }
    ]
  }
});

const Tutorial = mongoose.model('Tutorial', tutorialSchema);

module.exports = Tutorial;

我想知道导致无限循环的原因，为什么它对查询有效但对模型无效？谢谢！

修改

这是有效的代码

Tag.js

const mongoose = require("mongoose");

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

tagSchema.virtual("tutorials", {
  ref: "Tutorial",
  foreignField: "tags",
  localField: "_id"
});

const Tag = mongoose.model("Tag", tagSchema);

module.exports = Tag;

Tutorial.js

const mongoose = require('mongoose');

const tutorialSchema = new mongoose.Schema({
  title: {
    type: String,
    required: true,
    unique: true,
    trim: true
  },
  tags: {
    type: [
      {
        type: mongoose.Schema.ObjectId,
        ref: 'Tag'
      }
    ]
  }
});

const Tutorial = mongoose.model('Tutorial', tutorialSchema);

module.exports = Tutorial;

TagController.js

const Tag = require('./../models/tagModel');

exports.getAllTags = async (req, res) => {
  try {
    const docs = await Tag.find().populate({
      path: 'tutorials',
      select: '-__v'
    });

    res.status(200).json({
      // some code
    });
  } catch(err) => {
    // some code
  }
});

Answer 1

我最近遇到了一个相同的问题，花了相当长的时间才弄清楚，在我的情况下，两个查询相互填充并导致无限循环。