Delete an array element from a document with Mongoose

Question

I am having a schema called ReferralHistory. It contains set of users and array of referred users.

ReferralHistory

var mongoose = require('mongoose');
var refferalHistorySchema = new mongoose.Schema({
    user: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'User',
        unique: true
    },

    referrals: [{
        type: mongoose.Schema.Types.ObjectId,
        ref: 'User'
    }],
});
var ReferralHistoryModel = mongoose.model('ReferralHistory', refferalHistorySchema);
module.exports = {
    referralHistory: ReferralHistoryModel
}

I need to delete a particular user from referrals array in the collection ReferralHistory[Here i only know id of referred user].How can i achieve this?

Edit

Collection

I tried

db.referralhistories.update({ "u_referrals": "593281ef966d7f0eeb94db3d" }, { "$pull": { "u_referrals": "593281ef966d7f0eeb94db3d" } });

O/P

But document is not updating.

Answer 1

You use the $pull operator with .update(). So assuming referredId as the value you know

ReferralHistoryModel.update(
  { "referrals": referredId },
  { "$pull": { "referrals": referredId } },
  { "multi": true },
  function(err,status) {

  }
)

Noting the { "multi": true } means the update can be applied to more than one matched document in the collection. If you really only intend to match and update one document then you don't include that option since updating only the first match is the default.

If you want to be more specific and also have the "user" to match, then you can do:

ReferralHistoryModel.update(
  { "user": userId, "referrals": referredId },
  { "$pull": { "referrals": referredId } },
  { "multi": true },
  function(err,status) {

  }
)

And then the match needs both values to be present as opposed to any ReferralhistoryModel documents which matched the referredId you supplied.