使用 Mongoose 通过 _id 查找

Question

I am having trouble with a simple findById with mongoose.

Confirmed the item exists in the DB

db.getCollection('stories').find({_id:'572f16439c0d3ffe0bc084a4'})

With mongoose

  Story.findById(topic.storyId, function(err, res) {
    logger.info("res", res);
    assert.isNotNull(res);
  });

won't find it.

I also tried converting to a mongoId, still cannot be found (even though mongoose supposedly does this for you)

var mid = mongoose.Types.ObjectId(storyId);
let story = await Story.findOne({_id: mid}).exec();

I'm actually trying to use this with typescript, hence the await.

I also tried the Story.findById(id) method, still cannot be found.

Is there some gotcha to just finding items by a plain _id field? does the _id have to be in the Schema? (docs say no)

I can find by other values in the Schema, just _id can't be used...

---

update: I wrote a short test for this.

describe("StoryConvert", function() {


  it("should read a list of topics", async function test() {
    let topics = await Topic.find({});

    for (let i = 0; i < topics.length; i ++) {
      let topic = topics[i];
    // topics.forEach( async function(topic) {
      let storyId = topic.storyId;
      let mid = mongoose.Types.ObjectId(storyId);
      let story = await Story.findOne({_id: mid});
      // let story = await Story.findById(topic.storyId).exec();
      // assert.equal(topic.storyId, story._id);
      logger.info("storyId", storyId);
      logger.info("mid", mid);
      logger.info("story", story);
      Story.findOne({_id: storyId}, function(err, res) {
        if (err) {
          logger.error(err);
        } else {
          logger.info("no error");
        }
        logger.info("res1", res);
      });

      Story.findOne({_id: mid}, function(err, res) {
        logger.info("res2", res);
      });

      Story.findById(mid, function(err, res) {
        logger.info("res3", res);
        // assert.isNotNull(res);
      });

    }

  });


});

It will return stuff like

Testing storyId 572f16439c0d3ffe0bc084a4

Testing mid 572f16439c0d3ffe0bc084a4

Testing story null

Testing no error

Testing res1 null

Testing res2 null

Testing res3 null

I noticed that topic.storyId is a string not sure if that would cause any issues mapping to the other table. I tried also adding some type defs

  storyId: {
    type: mongoose.Schema.Types.ObjectId,
    required: false
  }

Answer 1

Because this query finds the doc in the shell:

db.getCollection('stories').find({_id:'572f16439c0d3ffe0bc084a4'})

That means that the type of _id in the document is actually a string, not an ObjectId like Mongoose is expecting.

To find that doc using Mongoose, you'd have to define _id in the schema for Story as:

_id: { type: String }

Answer 2

If your Mongo schema is configured to use Object Id, you query in nodeJS using

models.Foo.findById(id)

where Foo is your model and id is your id. here's a working example

router.get('/:id', function(req, res, next) {
    var id = req.params.id
    models.Foo.findById(id)        
        .lean().exec(function (err, results) {
        if (err) return console.error(err)
        try {
            console.log(results)            
        } catch (error) {
            console.log("errror getting results")
            console.log(error)
        } 
    })
})

In Mongo DB your query would be

{_id:ObjectId('5c09fb04ff03a672a26fb23a')}

Answer 3

One solution is to use mongoose.ObjectId()

const Model = require('./model')
const mongoose = require('mongoose')

Model.find({ id: mongoose.ObjectId(userID) })

It works, but it is weird because we are using id instead of _id

Answer 4

I got into this scenario too. This was how I solved it;

• According to the mongoose documentation , you need to tell mongoose to return the raw js objects, not mongoose documents by passing the lean option and setting it to true. eg

Adventure.findById(id, 'name', { lean: true }, function (err, doc) {});

in your situation, it would be

Story.findById(topic.storyId, { lean: true }, function(err, res) {
    logger.info("res", res);
    assert.isNotNull(res);
});

Answer 5

If _id is the default mongodb key, in your model set the type of _id as this:

_id: mongoose.SchemaTypes.ObjectId

Then usind mongoose you can use a normal find:

YourModel.find({"_id": "5f9a86b77676e180c3089c3d"});

Answer 6

models.findById(id)

TRY THIS ONE . REF LINK : https://www.geeksforgeeks.org/mongoose-findbyid-function/

Answer 7

This is how we do it now:

const { mongoose } = require("mongoose");
YourModel.find({ _id: mongoose.Types.ObjectId("572f16439c0d3ffe0bc084a4") });

Answer 8

Try this

 Story.findOne({_id:"572b19509dac77951ab91a0b"}, function(err, story){
                if (err){
                    console.log("errr",err);
                    //return done(err, null);
                }else{
                    console.log(story);
                }

 });