Insert an unique object in an object array with mongoose

Question

I'm inserting an object in an array of object with mongoose. My object is like:

   name: {
    type: String,
    unique: true,
    required: true
},
translations: [{
    tag: {
        type: String,
        unique: true,
        required: true
    },
    meaning: {
        type: String,
        required: true
    }
}]

I would like my code to throw an error when there are already an object in "translation" with the same 'tag' value.

I'm currently doing this :

Language.update(
    {name: languageName},
    {$addToSet: { 'translations': {
        tag: aNewTag,
        meaning: aNewTranslation
    }}}, {
        upsert: false
    }, function(err) {
        if (err) console.log(err);
        else console.log('This is spartaaa!!!');
    }
);

I don't think this is possible with one operation in MongoDb. You will have to check the document first, and then update or throw the exception. — Josh C.
– Josh C., Commented Mar 2, 2014 at 23:10
It think you are missing the meaning of $addToSet. The point is that it will keep things unique. Anything value you pass in that is already there will not update the array/set. If your items are not unique already, you don't have a set. — Neil Lunn
– Neil Lunn, Commented Mar 3, 2014 at 0:58

Dennis van der Schagt · Accepted Answer · 2015-05-29 21:17:39Z

1

You could check the WriteResult in the update callback and then throw an error if there was no modification, like this:

Language.update(
  {
    name: languageName
  }, {
    $addToSet: {
      'translations': {
        tag: aNewTag,
        meaning: aNewTranslation
  }}}, {
    upsert: false
  }, function(err, result) {
    if (err) {
      console.log(err);
    } else if (result.nModified === 0) {
      throw Error('Object is not unique, no duplicate inserted.');
    } else {
      console.log('This is spartaaa!!!');
    }
});

More information about the WriteResult for updates can be found in the mongoose documentation.

edited May 29, 2015 at 21:17

answered May 29, 2015 at 9:57

Dennis van der Schagt

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