当引用正确时，猫鼬填充返回空数组

Question

我已经在VisionModel.js和PictureModel.js中创建了以下两个模型Vision和Picture：

if (Game.Player.Character.GetVehicleIsTryingToEnter() == stretch && isEnteringCar == false)
        {
            isEnteringCar = true;
            Game.Player.Character.Task.EnterVehicle(stretch, VehicleSeat.RightRear);
            isEnteringCar = false;
        }

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

var visionSchema = new Schema({
    title: String,
    pictures: [{ type: Schema.Types.ObjectId, ref: 'Picture' }]

}, { timestamps: true });

module.exports = mongoose.model('Vision', visionSchema, 'visions');

现在，当我获得Vision文档时，我希望将所有图片附加到该文档中：

var mongoose = require('mongoose');

var Schema = mongoose.Schema;

var pictureSchema = new Schema({
    visionId: {type: Schema.Types.ObjectId, ref: 'Vision'},
    formatOriginalUrl: String
    
}, { timestamps: true });
module.exports = mongoose.model('Picture', pictureSchema, 'pictures');

但是它不起作用，并返回图片的空数组

{

    VisionModel
    .findById("5cfbb1fbdc38da8f145a8d41")
    .populate('pictures')

    .exec(function (err, result) {
        res.send(result);
     });

}

我找不到错误，我们将不胜感激。