How to set an property of a specific object in an array? mongodb

Question

I have a mongodb document, for a project object:

{
  members: [
    { _id: ObjectId(1), 
      active: true },
    { _id: ObjectId(2),
      active: false }
  ]
}

I'd like to change project.members[1].active = true , while only knowing ObjectId(2) during the initial query. Is there a way to do this without using findOne and manually looping over the members array and checking for equivalence of the ObjectId?

Answer 1

This works. The stuff after this section may work in the future.

Using http://docs.mongodb.org/manual/reference/operator/update/positional/ , I figured it out.

db.collection('projects').findAndModify(
  {                                                          // Query
    "_id": ObjectId(id),
    "members._id": ObjectId(user_id) 
  },
  [[]],                                                      // Ordering
  {                                                          // Update parameters
    $set: { "members.$.active": true }
  }, 
  {new: true},                                               // Options
  function(err, project) {
    // do stuff
});

Since the $ positional operator selects the first query match, it'll $set the active property for only that object in the array.

UPDATE: The following won't work... yet. $pull and $push cannot be used simultaneously currently, but is under consideration .

"err": "Field name duplication not allowed with modifiers"

I think I can use a $pull and a $push to achieve what I need.

db.collection('projects').findAndModify(
  {                                                          // Query
    "_id": ObjectId(id),
    "members": { $elemMatch: { _id: ObjectId(user_id) } } },
  [[]],                                                      // Ordering
  {                                                          // Update parameters
    $pull: { "members": { $elemMatch: { _id: ObjectId(user_id) } } }, 
    $push: { "members": ObjectId(user_id), active: true }
  }, 
  {new: true},                                               // Options
  function(err, project) {
    // do stuff
});

The "members" line of the query is optional - adding this line will restrict the update so that only users already in the members array can get changed. If it is removed, then running this will overwrite or create a new member.