Mongoose 填充多个文档不起作用？

Question

以下是我的模型。我想将碎片集合中的数据填充到我的流中。

流：

var mongoose = require("mongoose");
var mongoosePaginate = require('mongoose-paginate');
var Schema = mongoose.Schema;

// Declare schema
var streamSchema = Schema({
    user_id: {
        type: String,
        required: true
    },
    public_key: {
        type: String
    },
    private_key: {
        type: String
    },
    title: {
        type: String,
        required: true
    },
    description: {
        type: String,
        required: true
    },
    particle: [{
        type: Schema.Types.ObjectId,
        ref: 'Piece'
    }],
    created_at: {
        type: Date,
        default: Date.now,
        index: 1 // Note 1
    },
});

streamSchema.plugin(mongoosePaginate);

// Export schema
// Model.paginate()
mongoose.model("Stream", streamSchema);

片断：

var mongoose = require("mongoose");
var mongoosePaginate = require('mongoose-paginate');

// Declare schema
var pieceSchema = new mongoose.Schema({
    stream_id: {
        type: String,
        required: true
    },
    particle: {
        type: Object
    },
    order: {
        type: Number,
        default: 1
    },
    entries_number: {
        type: Number,
        default: 0
    },
    last_entry_at: {
        type: Date
    },
    created_at: {
        type: Date,
        default: Date.now,
        index: 1 // Note 1
    },
});

pieceSchema.plugin(mongoosePaginate);

// Export schema
// Model.paginate()
mongoose.model("Piece", pieceSchema);

我的查询：

Stream
.findOne({
    public_key: publicKey
})
.select("-data -weather -location")
.populate('particle', 'particle') // only return the particle
.exec(function (err, stream) {
  if (err) return handleError(err);

  console.log(stream);

});

结果：

{ _id: 580f69e0922112dd54a9f4e1,
  user_id: '579f52bc53d9e8cc14f504da',
  title: 'Dustbox 108',
  description: '....',
  public_key: 'HIGENfU96Hejy7y',
  private_key: 'RcWrwGaGpDVHO4WQ',
  alias: 'dustbox_108',
  __v: 0,
  created_at: 2016-10-25T14:19:12.008Z,
  particle: []
 }

我追求的结果：

{ _id: 580f69e0922112dd54a9f4e1,
user_id: '579f52bc53d9e8cc14f504da',
title: 'Dustbox 108',
description: '....',
public_key: 'HIGENfU96Hejy7y',
private_key: 'RcWrwGaGpDVHO4WQ',
alias: 'dustbox_108',
__v: 0,
created_at: 2016-10-25T14:19:12.008Z,
particle: [{
        "timestamp" : [ 
            1490385416748.0, 
            1490385457814.0
        ],
        "PM" : [ 
            null, 
            null
        ],
        "Particles" : [ 
            "100", 
            "100"
        ]
    }]
}

有可能吗？

这是 Piece 模型的示例文档：

{
    "_id" : ObjectId("58d57a08b2541e37c7fe5827"),
    "stream_id" : "580f69e0922112dd54a9f4e1",
    "particle" : {
        "timestamp" : [ 
            1490385416748.0, 
            1490385457814.0
        ],
        "PM" : [ 
            null, 
            null
        ],
        "Particles" : [ 
            "100", 
            "100"
        ]
    },
    "created_at" : ISODate("2017-03-24T19:56:56.735Z"),
    "entries_number" : 2,
    "order" : 1,
    "__v" : 0,
    "last_entry_at" : ISODate("2017-03-24T19:57:37.814Z")
}

有什么想法吗？

编辑：

最新输出：

...
particle: [ { _id: 58d57a08b2541e37c7fe5827, particle: [Object] } ],
...

仍然不是我想要的......

Answer 1

因为“粒子”字段是指子文档的字段，它本身就是一个对象，您必须在两个级别上填充。

.populate({
    path: 'particle',
    populate: { path: 'piece.particle' }
  })

查看文档（跨多个级别填充）：http://mongoosejs.com/docs/populate.html