使用 findOneAndUpdate $pull 并填充不更新或填充

Question

这是我的数据：

{
    "_id" : ObjectId("594e762b03cc52508686ceef"),
    "_members" : [ 
        "59527bd5e521801bf07eab98", 
        "594ecca47a699d1775c2a2db"
    ],
}

我想59527bd5e521801bf07eab98从_members.

后架构：

const PostsSchema = new Schema({
    // ...
    _members: [{ type: Schema.Types.ObjectId, ref: 'user' }],
    // ...
})

用户架构：

const UserSchema = new Schema({
    // ...
    posts : [{ type: Schema.Types.ObjectId, ref: 'post' }],
    // ...
})

查找和更新：

let id = mongoose.mongo.ObjectID(req.params.id)
let member = mongoose.mongo.ObjectID(req.params.member)
let populateQuery = [
    {path:'_members', select:'_id'}
]

Post.
findOneAndUpdate(
    {'_id' : id} ,
    {
       $pull: { '_members': { '_id': member }}
     },
     {'new': true}
).
populate(populateQuery).
exec(
  function (err, data) {
    res.send(data)
  }
);

Answer 1

有趣的是model，.populate()在这种情况下，“人口”似乎只能通过指定选项来工作。

此外，您只需要member直接提供 ，$pull因为_id实际上不是属性，直到“填充”。该"_members"数组只是ObjectId其Post自身内的一个值数组。所以直接提供输入：

Post.findOneAndUpdate(
  {'_id' : id} ,
  {
    $pull: { '_members': member }
  },
  {'new': true}
)
.populate({path:'_members', select:'_id', model: 'user' })
.exec(function(err,post) {
  if (err) throw err; // or something
  res.send(post)
})

或与承诺

Post.findOneAndUpdate(
  {'_id' : id} ,
  {
    $pull: { '_members':  member }
  },
  {'new': true}
)
.populate({path:'_members', select:'_id', model: 'user' })
.then(post => res.send(post))
.catch(err => console.error(err));  // or something

交替调用Model.populate()：

Post.findOneAndUpdate(
  {'_id' : id} ,
  {
    $pull: { '_members': member }
  },
  {'new': true}
).exec(function(err,post) {
  if (err) throw err; // or something

  Post.populate(post, {path:'_members', select:'_id', model: 'user' },function(err,post) {
    if (err) throw err; // or something
    res.send(post);   // now populated
  }
})

或者交替使用承诺：

Post.findOneAndUpdate(
  {'_id' : id} ,
  {
    $pull: { '_members': member }
  },
  {'new': true}
)
.then(post => Post.populate(post, {path:'_members', select:'_id', model: 'user' }))
.then(post => res.send(post))      // also populated
.catch(err => console.error(err))    // or whichever

.populate()当您只要求返回_id已嵌入文档中的字段时，有点不确定为什么要调用，但这是另一种情况。有了这个model选项，人口实际上发生在这里。

作为一个独立的演示：

const async = require('async'),
    mongoose = require('mongoose'),
    Schema = mongoose.Schema;

mongoose.Promise = global.Promise;
mongoose.set('debug',true);
mongoose.connect('mongodb://localhost/test');

const relSchema = new Schema({ c: String });
const testSchema = new Schema({
  a: String,
  b: [{ type: Schema.Types.ObjectId, rel: 'Rel' }]
})

const Test = mongoose.model('Test', testSchema);
const Rel = mongoose.model('Rel', relSchema);

function log(data) {
  console.log(JSON.stringify(data, undefined, 2))
}

async.series(
  [
    (callback) =>
      async.each(mongoose.models,(model,callback) =>
        model.remove({},callback),callback),

    (callback) =>
      async.waterfall(
        [

          (callback) => Rel.create([{ c: 2 },{ c: 3 },{ c: 4 }],callback),


          (rels,callback) => Test.create({ a: 1, b: rels },(err,test) => {
            if (err) callback(err);
            log(test);
            callback(err,test.b.slice(1,3))
          }),

          (rels,calback) =>
            Test.findOneAndUpdate(
              { 'a': 1 },
              { '$pull': { 'b': rels[0] } },
              { 'new': true }
            )
            .populate({ path: 'b', model: 'Rel' })
            .exec((err,test) => {
              if (err) callback(err);
              log(test);
              callback(err);
            })

        ],
        callback
      )

  ],
  (err) => {
    if (err) throw err;
    mongoose.disconnect();
  }
)

和输出：

Mongoose: tests.remove({}, {})
Mongoose: rels.remove({}, {})
Mongoose: rels.insert({ c: '2', _id: ObjectId("595714579afd8860e56d2ec7"), __v: 0 })
Mongoose: rels.insert({ c: '3', _id: ObjectId("595714579afd8860e56d2ec8"), __v: 0 })
Mongoose: rels.insert({ c: '4', _id: ObjectId("595714579afd8860e56d2ec9"), __v: 0 })
Mongoose: tests.insert({ a: '1', _id: ObjectId("595714579afd8860e56d2eca"), b: [ ObjectId("595714579afd8860e56d2ec7"), ObjectId("595714579afd8860e56d2ec8"), ObjectId("595714579afd8860e56d2ec9") ], __v: 0 })
{
  "__v": 0,
  "a": "1",
  "_id": "595714579afd8860e56d2eca",
  "b": [
    "595714579afd8860e56d2ec7",
    "595714579afd8860e56d2ec8",
    "595714579afd8860e56d2ec9"
  ]
}
Mongoose: tests.findAndModify({ a: '1' }, [], { '$pull': { b: ObjectId("595714579afd8860e56d2ec8") } }, { new: true, upsert: false, remove: false, fields: {} })
Mongoose: rels.find({ _id: { '$in': [ ObjectId("595714579afd8860e56d2ec7"), ObjectId("595714579afd8860e56d2ec9") ] } }, { fields: {} })
{
  "_id": "595714579afd8860e56d2eca",
  "a": "1",
  "__v": 0,
  "b": [
    {
      "_id": "595714579afd8860e56d2ec7",
      "c": "2",
      "__v": 0
    },
    {
      "_id": "595714579afd8860e56d2ec9",
      "c": "4",
      "__v": 0
    }
  ]
}