Updating an array item using NodeJS, MongoDB & Monk

Question

I have a data set like this:

{ 
  name : 'Doc Name',
  photos: [
      {
        name: 'photo1',
        url: 'http://.....'
      },
      {
        name: 'photo2',
        url: 'http://......'
      }
   ],
   etc ...

Using Monk https://github.com/LearnBoost/monk how do I update photo2? I can use an index as I am iterating over the fields at the moment.

My current attempt below gives me an error, and I can't use a variable for the JSON selector (as in the index).

collection.update({_id: data._id}, {photos[i].data: filename}, function(err, updatedata) {

            });

Peculium

Answer 1

Updating items at a position in an array can be done using the positional $ operator

collection.update( 
    { _id: data.id, "photos.name": "photo2" }, 
    { $set: { "photos.$.data": "yourdata" } }
)

Cerecloth

Of note, this only works when ONE (1) sub-document is found. If you want to update more than 1 sub-document, go vote for the bug. jira.mongodb.org/browse/SERVER-1243 – Sepaloid

@Sepaloid Technically that was a "feature request" and it's actually been fulfilled. There is of course a different question about that particular request How to Update Multiple Array Elements in mongodb, of which that link there is my answer on how you actually do that with the new MongoDB feature. – Cerecloth

Answer 2

So I found a solution to my problem but there may be some better options and I will leave it unanswered. But for anyone else with the same issue this is what I did:

I extracted the MongoDB document as an object in Node.js, manipulated the document, and then replaced the entire array in a single update statement. For example here is some pseudo code:

collection.find({id: 1}, function(err, doc){
    for(i=0; i< doc.array.length; i++) {
          //do what you gotta do
          doc.array[i].property = 'new value';
    }
    collection.update({id: 1}, {$set : {"doc.array": doc.array}}, function(err,doc){
          console.log(err);
    }
})

Peculium