What is the best way get subdocument's property with ObjectId?

Question

What is the best way get subdocument's property with ObjectId?

I have 2 collections: Docs and Types. In Docs i have document:

{
    '_id': ObjectId('0000'),
    'name': 'someName',
    'type': ObjectId('1111') // id i have
}

In Types:

{
    '_id': ObjectId('2222'),
    'for': 'Docs',
    'types': [
        {
            '_id': ObjectId('1111'), // type i need
            'name': 'someType' // want to get this name
        }
         // , and so on
    ]
}

After Docs.findOne({_id: '0000'}) i have type = ObjectId('1111') (id of 'someType'). What is the best way to get someType's name value?

javascript
node.js
mongodb
mongoose

Answer 1

You can use the $ positional operator in your field selection parameter to findOne to pull out just the matching element:

Types.findOne({'types._id': someTypeId}, {'types.$': 1}, function (err, type) {
    if (type) {
        console.log('Type name is: ' + type.types[0].name);
    }
});