Processing JSON creates a normal array instead of JSON object

Question

The JSON coming from an external web API looks like this:

[{matches:
    [{
      "match_something":"123",
      "match_something_else":"Potato",
      "match_events":
      [{
          "event_id":"42",
          "event_desc":"redcard",
       },
       {
           "event_id":"1",
           ..
      }]
    },
    // more matches

So, match array with an event array within it for each match.

The relevant processing code looks like this:

        _.each(matches, function(match) {
            var results = new Results({
                _id: match.match_id,
                match_date: match.match_formatted_date,
                ft_score: match.match_ft_score,
                match_events:[]
            });
            events = match.match_events;
            _.each(events, function(event) {
               results.match_events.push({
                   _id:event.event_id,
                   match_id:event.event_match_id,
                   type:event.event_type,
                   team:event.event_team,
                   player:event.event_player,
               });
            });
            results_array.push(results);
        });
        return results_array

This is the schema for the model (shortened for brevity):

var resultsSchema = new db.mongoose.Schema({
        _id:Number,
        match_date:String,
        status:String,
        ...
        match_events:[{
            _id: Number,
            match_id: Number,
            type:String,
            ...
        }]
    });

And then, what I see from my database (mongo) once this completes is the following JSON (removed extra attributes for clarity):

[
{"_id":1931559, "ft_score":"[0-0]","__v":0,
    "match_events":   
        ["19315591","19315592","19315593","19315594"]},

Which just has me baffled. The ID's are correct, I checked against the server data. And the processing code is just creating an array of these ID's, instead of a JSON object for each event.

Shouldn't it be shown as:

..."match_events":
    [{"_id:" "19315591", ...}]

I am not familiar with this database, but isn't the _id reserved? I mean are you sure you can define an object with _id in a nested structure? It seems like it interprets that as an internal link, or something like that. I'd try it out without _id... The code seems to be okay, so this is a strange bug... — inf3rno
– inf3rno, Commented Sep 5, 2014 at 2:14
Yep the problem was with the schema declaration as pointed out in the other answer below. I did remove the _id though just in case that would cause issues in the future. Thanks — goralph
– goralph, Commented Sep 5, 2014 at 2:21
@inf3rno Mongoose will use whatever "type" you declare explicitly for _id in the schema, or implicitly adds a ObjectId where you do not define it. It will even try to "cast" arguments supplied as a string to the correct type where it can. — Neil Lunn
– Neil Lunn, Commented Sep 5, 2014 at 2:52
I am not sure whether this is good or bad. I mean it is hard to debug if there are no error messages... At least it should send a console.warn()... — inf3rno
– inf3rno, Commented Sep 5, 2014 at 2:59

Neil Lunn · Accepted Answer · 2014-09-05 02:15:52Z

3

Your schema definition is the problem here. Mongoose uses the "type" keyword to determine the datatype, so it thinks that "match_events" is an array of "String".

Declare like this instead:

var resultSchema = new Schema({
  _id: Number,
  status: String,
  match_events: [{
    _id: { type: Number },
    type: { type: String }
  }]
});

Or better yet like this:

var eventSchema = new Schema({
  _id: Number,
  type: String
});

var resultSchema = new Schema({
  _id: Number,
  status: String,
  match_events: [eventSchema]
});

answered Sep 5, 2014 at 2:15

Neil Lunn

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4 Comments

goralph Over a year ago

Worked like a charm straight away. Thank you for the extra effort with the second implementation. Also thanks again for the help Neil, appreciate it.

inf3rno Over a year ago

Nice, at least the reserved word part was true :-)

goralph Over a year ago

Ah actually! Just had a look and mongo assigned an _id to each internal structure when I had removed _id from the schema. So it looks like it's required :)

inf3rno Over a year ago

At least we know that too :-)

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