Mongoose - 聚合查找未按预期填充字段

Question

我有一个具有以下结构的帖子模型：

const postSchema = new mongoose.Schema(
    {
        caption: { type: String, maxLength: 2000 },
        creator: { type: mongoose.Schema.Types.ObjectId, ref: "User" },
    },
    { timestamps: true }
)

creator

字段引用

User model

，其结构如下：

const userSchema = new mongoose.Schema({
    username: {
        type: String,
        required: true,
    },
    followers: [
        {
            type: mongoose.Schema.Types.ObjectId,
            ref: "User",
        },
    ],
})

我对

aggregation

模型执行以下

Post

查询，以返回某些帖子，并填充

creator

字段。

creator

字段已填充，但是

followers

属性作为

ObjectIds

数组返回，但我也想填充

followers

字段。

当前聚合查询：

let postQuery = Post.aggregate([
    {
        $lookup: {
            from: "users",
            localField: "creator",
            foreignField: "_id",
            as: "creatorDoc",
        },
    },
    {
        $match: {
            "creatorDoc.username": username,
            "creatorDoc.followers": { $nin: [req.user._id] },
        },
    },
    {
        $project: {
            _id: 1,
            caption: 1,
            "creatorDoc.username": 1,
            "creatorDoc.followers": 1,
        },
    },
    {
        $unwind: "$creatorDoc",
    },
]).then((result) => {
    console.log(result)
    res.send(result)
})

结果：（请注意，我希望填充

followers

字段，但它返回一个对象 id 数组：

[
  {
    "_id": "66294f6765bf3ddfc42f0a9d",
    "caption": "dedededede",
    "creatorDoc": {
      // Username displays as expected
      "username": "sam",
      // I want to populate this array 
      "followers": [
        "6626753edc14c52c550834fd"
      ]
    }
  }
]

如何使用此

aggregation

查询填充关注者数组？谢谢。

Answer 1

参考“User”大写。你能像这个“用户”一样尝试吗？

const postSchema = new mongoose.Schema(
    {
        caption: { type: String, maxLength: 2000 },
        creator: { type: mongoose.Schema.Types.ObjectId, ref: "user" },
    },
    { timestamps: true }
)