Querying for Object in Mongoose Sub Array

问题

I have a Schema that looks like this:

var LibrarySchema = new Schema({
    id: String,
    contactNumber: String,
    collections: [{
        id: String,
        description: String
        subCollections: [{
            id: String,
            description: String,
            recentlyUpdated: Boolean
        }, {
            id: String,
            description: String,
            recentlyUpdated: Boolean
        }]
    }]
})

module.exports = mongoose.model('Library', LibrarySchema); 

All the ID's are unique. There can be multiple Libraries inside a District (another array).

My question is, how would I query into the nested arrays to get the desired object? To be more precise, how would I get a specific subCollection object, given a Library ID, Collection ID, and subCollection ID.

回答1:

You can use this query:

Library.find({
  'id': libraryID,
  'collections.id': CollectionID,
  'collections.subCollections.id': subCollectionID
}, { 'collections.subCollections.$': 1 }, function(err, data) {
  console.log(err, data);
})

来源：https://stackoverflow.com/questions/37666138/querying-for-object-in-mongoose-sub-array