Avoid push/addToSet null value to mongodb array

Question

When using $push or $addToSet operator in mongoose, and the value I give (friend.id) is null or undefined, it will push a null element to the array.

dbUser.findByIdAndUpdate(
 _id,
 {
  $addToSet: {
  'friendsBlackList': friendB.id ,
  'FriendsWhiteList': friendW.id ,
  },
  },
  { new: true, upsert: true }
});

How to avoid pushing a null element? Can it be controlled in the mongoose schema? Thank you for your suggestions.

Why can't you check the value of friend.id before issuing the query? — Sede
– Sede, Commented Nov 25, 2015 at 1:39
Yes, but What if there are two push operations? I updated my question — SrvfUser
– SrvfUser, Commented Nov 25, 2015 at 1:43
@Sulliwane You still didn't answer the question. It seems like the easiest way to do this is to check if the values you want to push are null beforehand. — David says Reinstate Monica
– David says Reinstate Monica, Commented Nov 25, 2015 at 2:44
@DavidGrinberg because I have two fields in the push operation, and sometimes friendB.id is null, but friendW.id is not. So even if I check the value beforehand, I cannot skip the operation (or it won't push the value that is not null). But maybe I should just split my push operations in two...so I can check value as suggested — SrvfUser
– SrvfUser, Commented Nov 25, 2015 at 2:48

David says Reinstate Monica · Accepted Answer · 2015-11-25 02:57:00Z

2

I'm not familiar with Mongoose and its syntax, but what your describing can be done with the following pseudocode:

var update = { $addToSet:{}};
if(friendB.id !=null){
    update.$addToSet.friendsBlackList = friendB.id
}
if(friendW.id !=null){
    update.$addToSet.friendsWhiteList = friendW.id
}

dbUser.findByIdAndUpdate(_id,update,{ new: true, upsert: true });

Some drivers (ie Morphia) have options you can set to ignore null and empty values. You should check if Mongoose has such options as well.

answered Nov 25, 2015 at 2:57

David says Reinstate Monica

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