Using Kotlin to parse nested json array/object

Question

I've read a few posts on here saying to use gson or something else. Android Kotlin parsing nested JSON

I am planning on switching to gson later but wondering how to parse with kotlin.

JSON object:

{
  "childScoresList": [
    {
      "child_id": "1",
      "score_date": "2022-03-27",
      "category_id": "1",
      "category_name": "Preschool Math",
      "classes": [
        {
          "category_name": "Preschool Math",
          "class_name": "Number Blocks",
          "class_id": "1",
          "class_description": "Ones, Tens, Hundreds Blocks used to create given numbers.",
          "skills": [
            {
              "skill_id": "1",
              "skill_name": "Place Value",
              "skill_description": "Knowing the place value of specific elements.",
              "skill_score": "50"
            }
          ]
        }
      ]
    }
  ]
}

Kotlin code:

val obj = JSONObject(response.toString())
val jsonArray = obj.getJSONArray("childScoresList")
for (i in 0 until jsonArray.length()) {
    val categoryName = jsonArray.getJSONObject(i).getString("category_name")
}

How do I get data in class_name? I tried various things but could not get it to work.

I'd prefer Jackson - it's the JSON library recommended by Spring. I'd guess that you have to walk the tree to get to class name: childScoresList[i].classes[j].class_name — duffymo
– duffymo, Commented Jun 2, 2022 at 16:59

Majid Ahmadi Jebeli · Accepted Answer · 2022-06-02 17:13:09Z

1

You must first get JSONArray from the object according to the following code and then access the class_name variable

val obj = JSONObject(js)
val jsonArray = obj.getJSONArray("childScoresList")
for (i in 0 until jsonArray.length()) {
    val classes = jsonArray.getJSONObject(i).getJSONArray("classes")
    for (x in 0 until classes.length()) {
        val categoryName = classes.getJSONObject(x).getString("category_name")
        val className = classes.getJSONObject(x).getString("class_name")
    }
}

answered Jun 2, 2022 at 17:13

Majid Ahmadi Jebeli

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2 Comments

IgorGanapolsky Over a year ago

How do we parse multiple objects in the array?

Majid Ahmadi Jebeli Over a year ago

@IgorGanapolsky With this line, you can see the objects inside the array: val object = jsonArray.getJSONObject(i)

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