如何在猫鼬中异步填充嵌套对象？

Question

I'm struggling with population in mongoose. Assuming I have a large document with many nested objects which not always got Schemas or are simply Type.Mixed.

A Schema for this document would be something like this:

{
    token: String,
    group: String,
    connectionStatus: String,
    activeQuestLine: String,
    quests:
    {
        exposition: [
            {
                content: { type: mongoose.Schema.Types.ObjectId, ref: 'Quest' },
                status: String,
                trigger:
                {
                    name: String,
                    param: mongoose.Schema.Types.Mixed
                },
                subQuests:
                [
                    {
                        content: { type: mongoose.Schema.Types.ObjectId, ref: 'Quest' },
                        status: String,
                        trigger:
                        {
                            name: String,
                            param: mongoose.Schema.Types.Mixed
                        }
                    }
                ]
            }
        ],
        conflict: [
            {
                content: { type: mongoose.Schema.Types.ObjectId, ref: 'Quest' },
                status: String
            }
        ],
        resolution: [
            {
                content: { type: mongoose.Schema.Types.ObjectId, ref: 'Quest' },
                status: String
            }
        ]
    },
    inventory:
    {
        maxSlots: Number,
        slots: [
            {
                itemType: String,
                content: mongoose.Schema.Types.Mixed,
                empty: Boolean
            }
        ]
    }
};

So I would ''findOne'' this type of document once, save it and then when needed populate certain parts for my specific use cases. As far as I can see most questions to this topic refer to saving the populated document after manipulating it, but I want to keep the document as it is and just pass the (populated) data to some other function.

For example I just want to get all ''subQuests'' of a certain quest of the exposition property. Where those could also have their ''subQuests'', yes there should be a recursive Schema, but for now this isn't the main problem. The problem is that I want to iterate over it like this:

async.forEachSeries(
   questInfo.subQuests,
   function (subQuestInfo, eachCallback)
   { 
       QuestManager.getQuest(subQuestInfo.content, function (subQuest)
       {
           if (!subQuest) throw 'SubQuest ' + subQuestInfo.content + ' not found';
           subQuestInfo.content = subQuest;
           eachCallback();
       });
   },
   function (err)
   {
       if (err) throw err;
       activeQuests.push(questInfo);
   });

With questInfo being extracted from the main document and passed as argument to that functionality. But at this line:

subQuestInfo.content = subQuest;

the value of 'content' is still just the ObjectId, so the previous value. My assignment has obviously no impact! It is a kind of manual population try, is there a better way to solve this?

Thank you for your time.

Answer 1

Assuming you have a Quest schema with quest.subQuests member, i'd go like this:

Quest.methods.getSubQuests = function(done) {
  var getSubQuestFns = this.subQuests.map(function(subQuest) {
    return QuestManager.getQuest.bind(QuestManager, subQuest.content)
  })
  async.parallel(getSubQuestFns, done)
}

// get some Quest instance
quest.getSubQuests(function(err, subQuests) {
  // whatever
})

(This won't modify the original quest doc.)