find by _id with Mongoose

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')}