Mongoose $pull operator not removing ObjectID from array

Question

In my application, I have a post schema (shown below):

const postSchema = new mongoose.Schema({
    file: {
        type: String,
        required: true
    },
    caption: {
        type: String,
        maxLength: 2000 
    },
    user: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'User'
    },
    likeNum: {
        type: Number,
        default: 0,
        min: 0
    },
    likes: [{
        type: mongoose.Schema.Types.ObjectId
    }]
})

I want to remove an objectid from the likes array when a user request is sent.

Route:

const post = await Post.findOne({_id: req.params.postid})
const user = req.user._id

post.update({}, {$pull: {likes: user}})
post.likeNum--
await post.save()
res.send('Unliked')

However the objectid is not removed from the array when the route is called. Can anyone spot why? Thanks.

UPDATE:

const user = mongoose.Types.ObjectId(req.user._id)

UPDATE 2:

Post.updateOne({_id: req.params.postid}, { $pull: { likes: mongoose.Types.ObjectId(req.user._id) } })
post.likeNum--
await post.save()
res.send('Unliked')

try converting _id to object id using mongoose.Types.ObjectId(req.user._id) — turivishal
– turivishal, Commented Feb 7, 2021 at 16:57
@turivishal Hello. This still has not removed the object id from the likes array. See update code above. — NodeReact020
– NodeReact020, Commented Feb 7, 2021 at 17:00
you are doing update operation on find object, just do separate query await Post.update({}, { $pull: { likes: mongoose.Types.ObjectId(req.user._id) } }) — turivishal
– turivishal, Commented Feb 7, 2021 at 17:02
@turivishal Hi this has still not worked. Please check updated code above — NodeReact020
– NodeReact020, Commented Feb 7, 2021 at 17:05
put await before query and no need to post.save() command because updateOne will save transaction, and if it still not work then try to convert your query {_id: mongoose.Types.ObjectId(req.params.postid)} — turivishal
– turivishal, Commented Feb 7, 2021 at 17:08

turivishal · Accepted Answer · 2021-02-07 17:16:01Z

5

You can do both operations in a single query no need to findOne,

convert req.user._id to object id using mongoose.Types.ObjectId
$inc to decrees the counts of likeNum

await Post.updateOne(
  { _id:  req.params.postid },
  {
    $pull: { likes: mongoose.Types.ObjectId(req.user._id) },
    $inc: { likeNum: -1 }
  }
);
res.send('Unliked');

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answered Feb 7, 2021 at 17:16

turivishal

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