Transform JSON objects to an new array

Question

How to transform JSON structure to an new array using Swift?

Initial JSON

{
  "group1": {
    "1/30/21": 100,
    "1/31/21": 200
  },
  "group2": {
    "1/30/21": 200,
    "1/31/21": 300
  },
  "group3": {
    "1/30/21": 300,
    "1/31/21": 500
  }
}

The array I'd like to convert would be like:

[
  {
    "group1": 100,
    "group2": 200,
    "group3": 300,
    "date": "1/30/21",
  },
  {
    "group1": 200,
    "group2": 300,
    "group3": 500,
    "date": "1/31/21",
  }
]

And how dynamic is the data, could there be more groups or more dates per group? Have you tried anything yourself you can share? — Joakim Danielson
– Joakim Danielson, Commented Feb 6, 2021 at 16:28
Yes, it could be more groups and more dates per group but each size of object is same — android1751
– android1751, Commented Feb 6, 2021 at 16:37

Joakim Danielson · Accepted Answer · 2021-02-06 18:22:48Z

2

First use JSONSerialization to convert the json to a dictionary

let dictionary = try JSONSerialization.jsonObject(with: jsonIn.data(using: .utf8)!) as! [String: [String: Int]]

Then in two steps convert to the expected format by first creating a dictionary where the date is the key and groups and numbers (as a tuples) are the values

var temp = [String: [(String, Int)]]()

dictionary.forEach { key, value in
    for (innerKey, innerValue) in value {
        temp[innerKey, default: []].append((key, innerValue))
    }
}

Then use this dictionary to create the array of dictionaries

let output = temp.map { (key, tuples) -> [String: Any] in
    var result = [String: Any]()
    for tuple in tuples {
        result[tuple.0] = tuple.1
    }
    result["date"] = key
    return result
}

and then back to json

let jsonOut = try JSONSerialization.data(withJSONObject: output)

edited Feb 6, 2021 at 18:22

answered Feb 6, 2021 at 18:16

Joakim Danielson

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