Mongoosejs Virtual populate不检索foregin集合

Question

这是答案集。

var mongoose = require("mongoose");
var answerSchema = new mongoose.Schema ({
    questionId:String,
    username:String,
    answered:Boolean
});


answerSchema.virtual('quest', {
ref: 'Question',
localField: 'questionId',
foreignField: '_id'
},{ toObject : {virtuals:true} }, { toJSON: { virtuals:true } });

及以下是我用来尝试填充＆＃34;问题＆＃34;的查询。基于id的模型。但是我只回复了＆＃34;答案＆＃34;收集，即使有基于foregin集合中的ID的数据。我究竟做错了什么 ？编辑：我使用的是Mongoose版本＆＃34; ^ 4.6.7＆＃34;

Answer.findOne({questionId:"58497379b0094008fe202b62"}).populate('quest').exec(function(error, vals) {
console.log(vals) }); // vals does not have the foregin collection related fields.