猫鼬填充引用返回未定义

Question

I am fairly new to mongoose so I have probably missed something here.

I have two Collections "Company" & "User" I am trying to get all Users who belong to a company but The users array on the company is returning undefined instead of what I would expect to be the user objects.

I have read through the documentation and populate seemed to be a step in the right direction however, it doesn't mention at any stage (that I could see) how to save into an array I assume I need to push the objects to the emails property on the user object?

I come from a very mysql heavy background and I maybe doing somethings incorrectly would appreciate if someone could explain how MongoDB handles relationships?

Company Schema

const companySchema = new Schema({
    name: String,
    slug: String,
    _creator: { type: Schema.Types.ObjectId, ref: 'User' },
    users: [{ type: Schema.Types.ObjectId, ref: 'User' }],
    created_at: Date,
    updated_at: Date
});

module.exports = mongoose.model('Company', companySchema);

User Schema

const userSchema = new Schema({
    first_name: String,
    last_name: String,
    username: String,
    password: String,
    companies: [{ type: Schema.Types.ObjectId, ref: 'Company' }],
    created_at: Date,
    updated_at: Date
});

module.exports = mongoose.model('User', userSchema);

Save the user

const dave = new User({
    first_name: 'Dave',
    last_name: 'Hewitt',
    username: 'moshie',
    password: '123456789',
    updated_at: new Date()
});

dave.save()
    .then(function (user) {
        const indigoTree = new Company({
            name: 'IndigoTree',
            slug: 'indigotree',
            _creator: dave._id,
            updated_at: new Date()
        });

        indigoTree.users.push(user);

        return indigoTree.save();
    })
    .then(function (company) {
        console.log(company);
    })
    .catch(function (error) {
        console.log(error);
    });

Check the user

Company.find({}).populate('users').exec()
   .then(function (doc) {
       doc.users // undefined?
   });

Any ideas?

Answer 1

As per API Docs , Mongoose's find() returns an array collections instead of single item.

For findOne() it is a potentially-null single document, find() a list of documents, count() the number of documents, update() the number of documents affected, etc

Company.find({}).populate('users').exec().then((doc) => {
    console.log(doc[0].users); // prints users array
});

Answer 2

You are pushing user into the users array. Instead of that you need to push user's Id into the array ie user._id .

Replace:

indigoTree.users.push(user);

With:

indigoTree.users.push(user._id);

Also, find() query returns array of documents , so you need to use doc[0].users , not doc.users .

Company.find({}).populate('users').exec()
   .then(function (doc) {
       doc[0].users // undefined? -> change here, it wont come undefined
   });

Alternatively , you can use findOne() instead of find() , which returns an object . In that case you can use doc.users

  Company.findOne({_id: someCompanyId}).populate('users').exec()
   .then(function (doc) {
       doc.users // it wont come undefined
   });