update dictionary value in swift 3

Question

{
  "error": false,
  "error_msg": "Get trending data.",
  "Total_category": 2,
  "responseData": [
    {
      "categoryName": "Trending",
      "Trending": [
        {
          "category": "Trending",
          "trailerPrice": "",
          "isFavourit": null,
          "isWatchlist": null
        }
      ]
    },
    {
      "categoryName": "Comedy",
      "Comedy": [
        {
          "category": "Comedy",
          "trailerPrice": "",
          "isFavourit": null,
          "isWatchlist": null
        }
      ]
    }

  ]
}

I need for updating the content for specific key **("isFavourit")**, How can possible in swift 3? Update only responseData-> index[1]->comedy[]-> "isFavourit" null to 1.

I can set the values of the dictionary like this responseData[1][Comedy]![0]["isFavourit"] = 1 not working in swift3.

How can set "isFavourit" value 1?

I just tried something like

(arrVideoDetail[1]["comedy"] as! [Dictionary<String,Any>])[0]["isFavourit"] = 1

Above code show error cannot assign to immutable expression of type 'Any?

Did you try searching Stack Overflow? You can't find anything about managing JSON data of this sort? — matt, Aug 09 '17 at 17:33
Consider to map the categories to custom objects (struct or class) and a name `isFavourit` implies to be `Bool` rather than `Int`. — vadian, Aug 09 '17 at 17:34

matt · Answer 1 · 2017-08-10T02:27:41.660

This is really bad JSON. The problem is that the dictionaries in the responseData array do not have consistent keys. The first has keys

  "categoryName": "Trending",
  "Trending": [

But the second has keys

  "categoryName": "Comedy",
  "Comedy": [

This means that you don't know the name of the second key until you've pulled out the value of the categoryName key. So you'll have to stop and do that before you can proceed.

So, let's suppose you have your JSON in a string called json. Then:

    let d1 = try! JSONSerialization.jsonObject(with: json.data(using: .utf8)!)
    let a1 = (d1 as! [String:Any])["responseData"]
    let d2 = (a1 as! [[String:Any]])[1]
    let key = d2["categoryName"] as! String // "Comedy"
    let a2 = d2[key]!
    var d3 = (a2 as! [[String:Any]])[0]
    // ["isWatchlist": <null>, "trailerPrice": , "isFavourit": <null>, "category": Comedy]

Now d3 is the inner dictionary you are looking for and you can modify it as desired.

By the way, this your JSON is a nice example of why this is all going to be so much nicer in Swift 4. We can parse the whole JSON into the properties of a custom struct:

struct MyJson : Decodable {
    let error : Bool
    let error_msg : String
    let Total_category : Int
    let responseData : [ResponseData]
    struct ResponseData : Codable {
        let categoryName : String
        let unknown : [Inner]
        struct Inner : Codable {
            let category : String
            let trailerPrice : String
            let isFavourit : String?
            let isWatchList : String?
        }
        private struct CK : CodingKey {
            var stringValue: String
            init?(stringValue: String) { self.stringValue = stringValue }
            var intValue: Int?
            init?(intValue: Int) { return nil }
        }
        init(from decoder: Decoder) throws {
            let con = try! decoder.container(keyedBy: CK.self)
            self.categoryName = try! con.decode(String.self, forKey:CK(stringValue:"categoryName")!)
            let key = self.categoryName
            self.unknown = try! con.decode([Inner].self, forKey: CK(stringValue:key)!)
        }
    }
}

Having configured our struct, parsing the entire JSON is just one line of code! Assume your JSON is in a variable called json:

let myjson = try JSONDecoder().decode(MyJson.self, from: json.data(using: .utf8)!)

And the value you are trying to access is expressible very simply:

let fav = myjson.responseData[1].unknown[0].isFavourit

So all I have to do is make all my let into var and now they are all settable, as you trying to do.

(For more about this solution, see Swift 4 Decodable with keys not known until decoding time.)

update dictionary value in swift 3

1 Answers1