MongoDB-更新对象数组中的数组

Question

I have the following structure:

    {
      data: [
        {pos:"0",
         moreData: ["a", "b"]
        },
        {pos:"1",
         moreData: ["a", "c"]
        },
    ]}

I would like to update the above structure with an update. I would like to add a letter to moreData where pos=1. This is how it should look like at the end:

    {
      data: [
        {pos:"0",
         moreData: ["a", "b"]
        },
        {pos:"1",
         moreData: ["a", "c", "d"]
        },
    ]}

I am doing this, at the moment: (using mongoose, but whatever would be fine)

    model.update({"data.pos":"1"},
                 { $push: {data:{ pos:"1", moreData:["d"] } } },
                 { safe: true, upsert: false }, function(err){
    });

All I'm getting is a duplicated "pos":"1" with a "moreData" containing only the new element "d". Any help would be highly appreciated. Thanks in advance!

Answer 1

There's something wrong with your data structure, {"data.pos": 1} selects the whole document (so $push doesn't act as expected):

> db.demo.find({"data.pos": "1"})
{ "_id" : ObjectId("533a850fd15748cc2dc1a17f"), "data" : [  {   "pos" : "0",    "moreData" : [  "a",    "b" ] },    {   "pos" : "1",    "moreData" : [  "a",    "c" ] } ] }

Try adding an id or something to your document:

> db.demo.find({"id": "foo"})
{ "_id" : ObjectId("533a85c9d15748cc2dc1a180"), "id" : "foo", "data" : [    {   "pos" : "0",    "moreData" : [  "a",    "b" ] },    {   "pos" : "1",    "moreData" : [  "a",    "c" ] } ] }
> db.demo.update({"id": "foo"}, {"$push": { "data" : { "pos": "2", "moreData": ["c", "d"]}}})
> db.demo.find({"id": "foo"})
{ "_id" : ObjectId("533a85c9d15748cc2dc1a180"), "data" : [  {   "pos" : "0",    "moreData" : [  "a",    "b" ] },    {   "pos" : "1",    "moreData" : [  "a",    "c" ] },    {   "pos" : "2",    "moreData" : [  "c",    "d" ] } ], "id" : "foo" }

Seems to do what you want.

Answer 2

The problem here is you need to push to the correct array element. You can either do this directly by dot notation and index value or by using the positional $ operator:

 model.update(
     {"data.pos": "1" },
     { "$push": { "data.$.moreData": "d" } },
     function(err, numAffected) {

 })

That should match the selected index of the "data" array in order to perform the update. Beware though, you have nested arrays and you would not be able to match and update an item in the inner array. See the positional operator documentation for this