猫鼬嵌套参考种群 [英] Mongoose nested reference population

问题描述

我无法理解 mongoose 的 populate 方法背后的一些概念.我首先采用了嵌入式方法，但由于担心大量数据开销和不同步的文档，我尝试将范式更改为 ref 其他文档.

I'm having trouble understanding some of the concepts behind mongoose's populate methods. I had an embedded approach working first, although, as I feared a big overhead of data and out-of-sync documents going around I tried changing the paradigm to ref other documents.

我的架构类似于以下(删除了不相关的属性):

My Schema is similar to the following (removed irrelevant properties):

var userSchema = mongoose.Schema({
    name: {type: String, default:''},
    favorites:{ 
        users:[{type: Schema.Types.ObjectId, ref: this}],
        places:[{type: Schema.Types.ObjectId, ref: PlaceSchema}]
    }
});

module.exports = mongoose.model('User', userSchema);

现在我正在尝试像这样获取用户的收藏夹:

Now I'm trying to get a User's favorites like this:

User.findOne({_id: currentUser}).exec(function(err, user){
  console.log(user);
  if (err)
    throw err;

  if(!user){
    console.log("can't find user");
  }else{ // user found
    user.populate('favorites.users');
    user.populate('favorites.places');

    // do something to the 'user.favorites' object

  }
});

虽然这没有按预期工作，因为 user.favorites.users 和 user.favorites.places 都未定义.

Although this doesn't work as intended, as both user.favorites.users and user.favorites.places come up undefined.

我认为我可以按上述方式填充，但显然，情况并非如此.从我读到的内容来看，我一定遗漏了一些指示(可能)ref 文档的模型的东西?这个流程对我来说很新，我有点迷茫.

I thought that I could populate as above, but apparently, that's not the case. From what I read, I must be missing something indicating (maybe) the model of the ref'ed document? This flow is very new to me and I'm kinda lost.

无论如何我可以通过填充我的查询结果来获得 users 和 places 的数组吗?我尝试将 populate 与 exec 链接起来，但它也不起作用.有没有更好的方法来达到这个结果?

Is there anyway I can get an array of users and places by populating my query result as above? I tried populate chained with exec and it doesn't work either. Is there a better way to achieve this result?

如果需要，在数据库中，User 文档显示为:

In case it's needed, in the DB, a User document shows up as:

{
  "_id": "56c36b330fbc51ba19cc83ff",
  "name": "John Doe",
  "favorites": {
    "places": [],
    "users": [
      "56b9d9a45f1ada8e0c0dee27"
    ]
  }
}

更多细节......我目前正在存储/删除这样的引用 ObjectIds(注意 targetID 是一个字符串):

A couple more details... I'm currently storing/removing the reference ObjectIds like this (note targetID is a String):

user.favorites.users.push({ _id: mongoose.Types.ObjectId(targetID)});
user.favorites.users.pull({ _id: mongoose.Types.ObjectId(targetID)});

另外，我需要用它们各自的文档以及填充users和places，我认为这在我的原始文件中可能不清楚问题.

Also, I need to populate the users and places with their respective documents aswell, I think that might not be clear in my original question.

推荐答案

好吧，我通过适当关注文档(以及@DJeanCar 的 (+1'd) 帮助/指针)找到了我需要的东西.

Well, I figured out what I needed by paying proper attention to the docs (and also with @DJeanCar 's (+1'd) help/pointers).

根据 Mongoose 的 docs 关于跨多个级别填充，我'已经达到了这个解决方案:

By Mongoose's docs regarding Populating across multiple levels, I've reached this solution:

User.findOne({_id: currentUser})
    .populate({path:"favorites.users", populate: "name"})
    .populate({path:"favorites.places", populate: "name"})
    .exec(function(err, user){
      if(err)
        throw err;

      if(!user){
        console.log("couldnt find source user");
      }else{
        // here, user.favorites is populated and I can do what I need with the data
      }
    });

此外，据我所知，您还可以在 populate() 的选项中传递 select: "field field field" ，如果您需要过滤填充后所需的文档字段.

Also, from what I could tell, you can also pass select: "field field field" in populate()'s options, should you need to filter the document fields you require after population.

希望这对有类似问题的人有所帮助！

Hope this helps someone with similar issues!

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