聚合来自不同模式的数据，其中一个模式具有数组类型对象

Question

我有 2 个不同的架构（即用户、帖子），用户有一个对象，即追随者，它是数组数据类型，我正在尝试聚合来自用户的所有帖子，这些用户具有 req.user.id 或登录“Followers”数组中的用户ID。

这是用户架构：

followers: [

{
  user: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "user",
  },
},]

这是我正在使用的获取请求：

try {

 const posts = await Post.aggregate([
   {
     $lookup: {
       from: "users",
       localField: "user",
       foreignField: "followers.user",
       as: "followers",
     },
   },{$match: {'followers.user' : req.user.id }}
])
res.json(posts);

这将返回：[ ] 作为输出

Answer 1

followers: [

  {
    user: {
     type: mongoose.Schema.Types.ObjectId,
     ref: "user",
  },
},]

如果上面的字段关注者在 Post 模式中，

 const posts = await Post.aggregate([
 {
   $lookup: {
     from: "users",
     localField: "followers.user",  <- field relation in Post
     foreignField: "_id", <- field objectId in users maybe "_id" 
     as: "followers",
   },
 },{$match: {'followers.user' : req.user.id }}
 ])

如果上面的字段关注者在用户模式中，

 const posts = await Post.aggregate([
 {
   $lookup: {
     from: "users",
     localField: "user",  <- field relation in Post
     foreignField: "_id", <- field objectId in users maybe "_id" 
     as: "user",
   },
   },{$match: {'user.followers.user' : req.user.id }}
 ])