Write to a nested schema nodejs mongoose using push

app.post('/comment', function(req, res){
    if (req.user) {
      models.users.findOne({name: req.user.username}, function(err, userdata){
        var picture = userdata.photo;
        var now = new Date();
        code_id = req.param('code_id');
        models.codes.findById(code_id, function(err, code){
          if (err) return handleError(err);
          code.comments.push({user: req.user.username, user_photo: picture, body: req.param('comment'), date_commented: now});
          var doc = code.comments[0];
          console.log(doc);
          code.save(function(err) {
            console.log('error check');
            if(err) { throw err; }
            console.log('saved');
            res.redirect('/code/'+code_id);
          });
        });
      });
    }
  });