mongoose Mongoose Population Simple Populate

Example

Mongoose populate is used to show data for referenced documents from other collections.

Lets say we have a Person model that has referenced documents called Address.

Person Model

var Person = mongoose.model('Person', {
    fname: String,
    mname: String,
    lname: String,
    address: {type: Schema.Types.ObjectId, ref: 'Address'}
});

Address Model

var Address = mongoose.model('Address', {
    houseNum: String,
    street: String,
    city: String,
    state: String,
    country: String
});

To populate Address inside Person using it's ObjectId, using let's say findOne(), use the populate() function and add the field key address as the first parameter.

Person.findOne({_id: req.params.id})
    .populate('address') // <- use the populate() function
    .exec(function(err, person) {
        // do something.
        // variable `person` contains the final populated data
    });

Or

Person.findOne({_id: req.params.id}, function(err, person) {
    // do something
    // variable `person` contains the final populated data
})
.populate('address');

The query above should produce the document below.

Person Doc

{
    "_id":"123abc",
    "fname":"John",
    "mname":"Kennedy",
    "lname":"Doe",
    "address":"456def" // <- Address' Id
}

Address Doc

{
    "_id":"456def",
    "houseNum":"2",
    "street":"Street 2",
    "city":"City of the dead",
    "state":"AB",
    "country:"PH"
}

Populated Doc

 {
    "_id":"123abc",
    "fname":"John",
    "mname":"Kennedy",
    "lname":"Doe",
    "address":{
        "_id":"456def",
        "houseNum":"2",
        "street":"Street 2",
        "city":"City of the dead",
        "state":"AB",
        "country:"PH"
    }
}