Update/Insert an element in a nested stringified array of a mongoDB document

Question

My collection has this structure:

{
    "_id" : "7ZEc8dkbs4tLwhW24",
    "title" : "title",
    "json" :

        {
            \"cells\":[
                {
                    \"type\":\"model\",
                    \"size\":{\"width\":100,\"height\":40},
                    \"id\":\"11dc3b6f-2f61-473c-90d7-08f16e7d277a\",
                    \"attrs\":{
                        \"text\":{\"text\":\"content\"},
                        \"a\":{\"xlink:href\":\"http://website.com\",\"xlink:show\":\"replace\",\"cursor\":\"pointer\"}
                    }
                }
            ]
        }
}

Now I need to insert/update the field json.cells.attrs.a in my meteor app. All informations I got are _id (document ID) and id (id of element in cells). If a doesn't exist, the element should be created.

My attempt is not correct, as the query isn't looking for the elemID to get the correct element in the cells-array:

var linkObject = {"xlink:href":"http://newURL.com","xlink:show":"replace","cursor":"pointer"};
var docID = '7ZEc8dkbs4tLwhW24';
var elemID = '11dc3b6f-2f61-473c-90d7-08f16e7d277a'; // How to search for this 'id'?

var result = Collection.findOne({ _id: docID });
var json = JSON.parse(result.json);

// find id = elemID in 'json'
// add/update 'a'

// update json in mongoDB document

Abdullah Rasheed · Accepted Answer · 2015-11-02 20:48:14Z

1

In your code you are only adding the docID as criteria in your query. You must add the elemID to your query criteria. Then after that you can use dot.notation and the $(Positional Operator) to update the a property of the attrs object. You can do it like this:

Collection.update(
    {"_id" : docID , "json.cells.id" : elemID },
    {$set: { "json.cells.$.attrs.a" : linkObject}}
}

$set, will create the field if the field does not exist. You can use the $ Positional Operator if you don't know the array position.

edited Nov 2, 2015 at 20:48

answered Nov 2, 2015 at 19:34

Abdullah Rasheed

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8 Comments

user3142695 Over a year ago

What does false and true mean?

Abdullah Rasheed Over a year ago

Check out my edited answer, but they were options. You can see how to add options in mongo > 2.6 here: docs.mongodb.org/manual/reference/method/db.collection.update/…

user3142695 Over a year ago

db.collection.find({"_id" : '7ZEc8dkbs4tLwhW24' , "json.cells.id" : '11dc3b6f-2f61-473c-90d7-08f16e7d277a' }).pretty() doesn't give me any result.

user3142695 Over a year ago

I just see that in the DB the data looks like: "json" : "{\"cells\":[... I think the slashes inside of json make some trouble, right?

Abdullah Rasheed Over a year ago

in the mongodb shell can you post how your data looks when you run. db.collection.find({"_id" : "7ZEc8dkbs4tLwhW24")})

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