Question

I have a schema like this (simplified)

var Language = new Schema({
    name: String
});
var PartOfSpeech = new Schema({
    name: String,
    language: { type: ObjectId, ref: "Language" }
});
var Attribute = new Schema({
    name: String,
    partOfSpeech: { type: ObjectId, ref: "PartOfSpeech" }
});

Is there an easy way to query MongoDB, such that given the _id of a language, it returns a result set containing all PartOfSpeech entries referencing that language, and all the Attribute entries referencing each part of speech?

The result set would look something like this:

[
   {
     name: "Noun",
     attributes: [
       { name: "Plural" },
       { name: "Possessive" }
     ]
   },
   {
     name: "Verb",
     attributes: [
       { name: "Past" },
       { name: "Future" }
     ]
   }
]

Is there a straightforward way to do this in Mongoose?

Answer 1

something like this

PartOfSpeech.find({ language: langId }, function (err, parts) {
  if (err) return done(err);

  var pending = parts.length;
  if (0 === pending) return done(null, parts);

  parts.forEach(function (part) {
    Attr.find({ partOfSpeech: part }, function (err, attributes) {
      if (err) return done(err, parts);
      part.attributes = attributes;
      if (--pending) return;
      done(null, parts)
    })
  });
})