CODEWITHSUNDEEP
mongodbmongoosemongoose-populate
Shih-Min Lee
Shih-Min Lee

Reputation: 9750

mongo mongoose populate subdocument returns null

I am trying to use node & mongoose's populate method to kind of 'join' 2 collections on query. The following is my schema setup: 

var mongoose = require('mongoose'),
Schema = mongoose.Schema;

var ShopSchema = new Schema({
  ssss: { type: Schema.Types.ObjectId, required :true, ref: 'Stat' },
  ratings: [RatingSchema]
});

var RatingSchema = new Schema({
  stat: { type: Schema.Types.ObjectId, required :true, ref: 'Stat' }
}, {_id: false});

Also I have setup the Stat mongoose model so that the queries works without error (but the result is not what I expected).

I tried to perform the following queries: 

ShopSchema.statics.load = function(id, cb) {
  this.findOne({
    _id: id
  }).populate('ssss', '_id stat_id').exec(cb);
};
mongoose.model('Shop', ShopSchema);

This gives me the correct result and the ssss is correctly referenced. The result is something like this .

"ssss":{"_id":"5406839ad5c5d9c5d47091f0","stat_id":1}

However, the following query gives me the wrong result. 

ShopSchema.statics.load = function(id, cb) {
  this.findOne({
    _id: id
  }).populate('ratings.stat', '_id stat_id').exec(cb);
};
mongoose.model('Shop', ShopSchema);

This gives me ratings.stat = null for all results. Could someone tell me what I did wrong? Thanks.

Upvotes: 1

Views: 1424

Answers (1)

Shih-Min Lee
Shih-Min Lee

Reputation: 9750

I just found the answer by trial and error..... in the last example ShopSchema is declared before the RatingSchema. So I am guessing Mongoose doesn't know exactly what is happening inside RatingSchema and making the populate returns an error. So if you declare RatingSchema before the ShopSchema and the populate method is working like a charm..

Upvotes: 1

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