Push object to a mongoose array and check for duplicate fields inside the array objects

Question

I am trying to push a notification object to a mongoDB array with the follow condition:

Check if there is a notification inside the array with the same postId If yes: return that object If no: create a new notification object

I'm using node with Mongoose ODM. In some other questions online they give this as an answer:

user.update({'notifications.postId': {$ne: post._id}}, {$push: { 'notifications': {type: 'POST', postId: post._id}}}, function(err, doc) {
  .....
});

But this didn't work for me.

Below you find the structure of the mongodb document.

{
    "_id": {
        "$oid": "56631b22067ee41847dab6bb"
    },
    "unreadNotifications": 0,
    "notifications": [
      {
        "type": "POST",
        "postId": {
          "$oid": "5666b78b61eb95bc03d47a71"
        },
        "_id": {
          "$oid": "56782daa395840efd4ed3f7a"
        },
        "createdAt": {
          "$date": "2015-12-21T16:49:46.903Z"
        },
        "events": []
      }    
    ]
    "created": {
        "$date": "2015-12-05T17:13:06.782Z"
    },
    "lastName": "Power",
    "firstName": "John",
    "__v": 0
}

@BobS Can you update your question to include your schema? That's key in figuring out why what you're trying isn't working. — JohnnyHK
– JohnnyHK, Commented Jan 1, 2016 at 16:46
you can try the answers given in this question stackoverflow.com/questions/13190370/… — ashishkumar148
– ashishkumar148, Commented Jan 2, 2016 at 12:02

MooYeol Prescott Lee · Accepted Answer · 2015-12-28 11:09:39Z

Note that Schema#update method will not updating records because there are no matched records described by specified match condition.

Anyway, You can create your own method on your User Schema.

Example

UserSchema.method('sendNotification', function (post, done) {
    var notification = null;

    for (var i = 0, len = this.notifications.length ; i < len ; i++) {
        notification = this.notifications[i];
        if (notification.postId.equals(post._id)) {
            return done(null, notification);
        }
    }

    notification = {
        type: 'POST',
        postId: post._id
    };

    this.update({
        $push: {
            notifications: notification
        }
    }, function (e, doc) {
        if (e) { return done(e); }
        return done(null, notification);
    });
});

You can use this method after model was created.

User.findOne({
    email: '[email protected]'
}).exec(function (e, john) {
    john.sendNotification(post, function (e, notification) {
        if (e) { console.log('Ah snap! There are an error.'); }
        console.log('notification: ', notification);
    });
});

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