In meteorjs with mongodb how do I set a var in an nested array

Question

How do I change the ans to other int and increase retry by 1 in courseList.quizScore on an update statement in mongodb with meteorjs?

Below is my query which is not working I am using $set, is this the correct operate to use? Can i use $set and $inc in the one update statement?

collection.jsx

Meteor.users.update({
    _id: Meteor.userId(),
    "courseList.courseId": courseId,
    "courseList.quizScore.qnNum": qnNum,
}, {
    $set: {
        "courseList.quizScore.$.ans": selectedAns
    }
})

mongoDB

{
  "_id": "yo8Mi2jKtoNSzgLDL",
  "courseList": [
    {
      "courseId": "nJmu5HW7g3wjWo47P",
      "classId": "3RniSRC3NurDRwZ2x",
      "quizScore": [
        {
          "qnNum": 0,
          "ans": 0,
          "retry": 1
        },
        {
          "qnNum": 1,
          "ans": 0,
          "retry": 1
        }
      ],
      "status": "Not Started"
    },
    {
      "courseId": "5ge2grte3wjWo4rh",
      "classId": "bffbeRC3NurDRtbf",
      "quizScore": [
        {
          "qnNum": 0,
          "ans": 1,
          "retry": 1
        },
        {
          "qnNum": 1,
          "ans": 2,
          "retry": 3
        }
      ],
      "status": "Not Started"
    }
  ]
}

zangw · Accepted Answer · 2016-03-21 10:06:25Z

1

There is an array within an array in your data, there is no easy way to reference the nested sub-array quizScore unless you know the position in this sub-array you want to update.

You can access the outer array courseList through $, and to access the inner array quizScore through position. Here is one sample code to update the first element of quizeScore matching courseId through using $set and $inc in one update statement.

Meteor.users.update(
          {_id: Meteor.userId(), 
          'courseList.courseId': courseId}, 
          {$set: {'courseList.$.quizScore.0.ans': selectedAns}, 
           $inc: {'courseList.$.quizScore.0.retry': 1}
          });

answered Mar 21, 2016 at 10:06

zangw

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