Dynamically create Meteor.js MongoDB query

For some reason I am having a hard time getting this to work. I have a Mongo collection called "cats" and another called "rows". The field cat

in 'cats' is currentCat

. Then I want to be able to update the document in "rows" by referencing an existing document from _id

. No problem. But for each, currentCat

I want to add an element to the document "rows" with currentCat

as a field and something else as a value ( currentPer

). I came up with this:

var cats = Cats.find({owner: Meteor.userId()}, {fields: {cat: 1, per: 1}});

cats.forEach(function(cats) { //Inserts the rest of the row
  var currentCat = cats['cat'];
  var currentPer = cats['per'];
  var currentAmount = Math.round(amount*currentPer*100)/100;

  Rows.update(
    { _id: row },
    { $push: { currentCat: currentAmount } }
  );
});

      

        
        
        
      

    

( row

is the ID of the document I want to change)

Of course it doesn't work as expected and just inserts ...{currentCat: 57}

instead of the variable's value currentCat

. Then I tried to create a request object (as described here ):

var query = ({ _id: row }, { $push: { currentCat: currentAmount } })

It also failed, but this time with a remarkably descriptive error message:

Error: Invalid modifier. Modifier must be an object.

Any help would be greatly appreciated, as I have spent hours and countless google searches (although the answer is probably obvious and I just can't see it - I'm still trying to get used to Meteor after PHP).

EDIT . I want the finished document to look something like this:

 { "_id" : "PshEYKebccw7eYaTo", 
   "createdAt" : ISODate("2014-11-26T00:52:51.840Z"),
   "cat1" : 312,
   "cat2" : 564,
   "owner" : "GiWCb8jXbPfzyc5ZF",
   "text" : "asdf" 
}