Mongoose populate nested array

问题

Assuming the following 3 models:

var CarSchema = new Schema({
  name: {type: String},
  partIds: [{type: Schema.Types.ObjectId, ref: 'Part'}],
});

var PartSchema = new Schema({
  name: {type: String},
  otherIds: [{type: Schema.Types.ObjectId, ref: 'Other'}],
});

var OtherSchema = new Schema({
  name: {type: String}
});

When I query for Cars I can populate the parts:

Car.find().populate('partIds').exec(function(err, cars) {
  // list of cars with partIds populated
});

Is there a way in mongoose to populate the otherIds in the nested parts objects for all the cars.

Car.find().populate('partIds').exec(function(err, cars) {
  // list of cars with partIds populated
  // Try an populate nested
  Part.populate(cars, {path: 'partIds.otherIds'}, function(err, cars) {
    // This does not populate all the otherIds within each part for each car
  });
});

I can probably iterate over each car and try to populate:

Car.find().populate('partIds').exec(function(err, cars) {
  // list of cars with partIds populated

  // Iterate all cars
  cars.forEach(function(car) {
     Part.populate(car, {path: 'partIds.otherIds'}, function(err, cars) {
       // This does not populate all the otherIds within each part for each car
     });
  });
});

Problem there is that I have to use a lib like async to make the populate call for each and wait until all are done and then return.

Possible to do without looping over all cars?

回答1:

Update: Please see Trinh Hoang Nhu's answer for a more compact version that was added in Mongoose 4. Summarized below:

Car
  .find()
  .populate({
    path: 'partIds',
    model: 'Part',
    populate: {
      path: 'otherIds',
      model: 'Other'
    }
  })

Mongoose 3 and below:

Car
  .find()
  .populate('partIds')
  .exec(function(err, docs) {
    if(err) return callback(err);
    Car.populate(docs, {
      path: 'partIds.otherIds',
      model: 'Other'
    },
    function(err, cars) {
      if(err) return callback(err);
      console.log(cars); // This object should now be populated accordingly.
    });
  });

For nested populations like this, you have to tell mongoose the Schema you want to populate from.

回答2:

Use mongoose deepPopulate plugin

car.find().deepPopulate('partIds.otherIds').exec();

回答3:

It's should be better with

Car
.find()
.populate({
    path: 'partIds.othersId'
})

来源：https://stackoverflow.com/questions/28179720/mongoose-populate-nested-array

标签

node.js

mongodb

mongoose

mongoose-populate