How to decode a JSON property with different types?

Question

I have a JSON

{
"tvShow": {
    "id": 5348,
    "name": "Supernatural",
    "permalink": "supernatural",
    "url": "http://www.episodate.com/tv-show/supernatural",
    "description": "Supernatural is an American fantasy horror television series created by Eric Kripke. It was first broadcast on September 13, 2005, on The WB and subsequently became part of successor The CW's lineup. Starring Jared Padalecki as Sam Winchester and Jensen Ackles as Dean Winchester, the series follows the two brothers as they hunt demons, ghosts, monsters, and other supernatural beings in the world. The series is produced by Warner Bros. Television, in association with Wonderland Sound and Vision. Along with Kripke, executive producers have been McG, Robert Singer, Phil Sgriccia, Sera Gamble, Jeremy Carver, John Shiban, Ben Edlund and Adam Glass. Former executive producer and director Kim Manners died of lung cancer during production of the fourth season.<br>The series is filmed in Vancouver, British Columbia and surrounding areas and was in development for nearly ten years, as creator Kripke spent several years unsuccessfully pitching it. The pilot was viewed by an estimated 5.69 million viewers, and the ratings of the first four episodes prompted The WB to pick up the series for a full season. Originally, Kripke planned the series for three seasons but later expanded it to five. The fifth season concluded the series' main storyline, and Kripke departed the series as showrunner. The series has continued on for several more seasons with Sera Gamble and Jeremy Carver assuming the role of showrunner.",
    "description_source": "http://en.wikipedia.org/wiki/Supernatural_(U.S._TV_series)#Spin-off_series",
    "start_date": "2005-09-13",
    "end_date": null,
    "country": "US",
    "status": "Running",
    "runtime": 60,
    "network": "The CW",
    "youtube_link": "6ZlnmAWL59I",
    "image_path": "https://static.episodate.com/images/tv-show/full/5348.jpg",
    "image_thumbnail_path": "https://static.episodate.com/images/tv-show/thumbnail/5348.jpg",
    "rating": "9.6747",
    "rating_count": "249",
    "countdown": null
}
}

The value of rating in different serials is Int ("rating": 0) or String ("rating": "9.6747").

I am parsing JSON with Codable/Decodable protocols:

struct DetailModel : Decodable {

var id : Int?
var name : String?
var permalink : String?
var url : String?
var description : String
var description_source : String?
var start_date : String?
var end_date : String?
var country : String?
var status : String?
var runtime : Int?
var network : String?
var youtube_link : String?
var image_path : String?
var image_thumbnail_path : String?
var rating: String
var rating_count : String?
var countdown : String?
var genres : [String]?
var pictures : [String]?
var episodes : [EpisodesModel]?
}

If rating == String, my code work and I have all the variables from JSON, but if rating == Int, all is nil. What should I do to parse all the types of variable rating at once Int and String?

My decodable function:

    func searchSerialDetail(id: Int, completion: @escaping (DetailModel?) -> Void){

    let parameters: [String: Any] = ["q": id]

    Alamofire.request(DetailNetworkLayer.url, method: .get, parameters: parameters).response { (jsonResponse) in

        if let jsonValue =  jsonResponse.data {
            let jsonDecoder = JSONDecoder()
                let detail = try? jsonDecoder.decode(DetailModel.self, from: jsonValue)
                completion(detail)
        }
    }
}

Thank you.

Why are almost all of `DetailModel`s properties optional? Only make them optional if they might not be present in the JSON. Moreover, make `rating` a `Double` and create a custom `init(from:)` method as explained in the linked Q&A to handle the conversion from `String` to `Double`. Also don't use `responseJSON` and don't mix `JSONSerialization` and `JSONDecoder`, simply take `response` from `Alamofire` as `Data` and parse that directly with `JSONDecoder`. With your current code you're parsing the JSON twice for no reason. — Dávid Pásztor, May 25 '18 at 10:05
No you didn't follow along the answer provided there. You should first go through the whole answer. Then you will understand what to implement for your case. You just scrolled through the answer and picked the first example. But the first example doesn't really solve that problem at all. Read the whole answer. — nayem, May 25 '18 at 11:45

Zonily Jame · Accepted Answer · 2018-05-26T09:36:30.047

11

You will have to implement your own func encode(to encoder: Encoder) throws and init(from decoder: Decoder) throws which are both properties of the Codable protocol. Then change your rating variable into an enum

Which would look like this:

enum Rating: Codable {
    case int(Int)
    case string(String)

    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        switch self {
        case .int(let v): try container.encode(v)
        case .string(let v): try container.encode(v)
        }
    }

    init(from decoder: Decoder) throws {
        let value = try decoder.singleValueContainer()

        if let v = try? value.decode(Int.self) {
            self = .int(v)
            return
        } else if let v = try? value.decode(String.self) {
            self = .string(v)
            return
        }

        throw Rating.ParseError.notRecognizedType(value)
    }

    enum ParseError: Error {
        case notRecognizedType(Any)
    }
}

Then on your DetailModel just change rating: String to rating: Rating

This works, I have tested with these JSON strings.

// int rating
{   
    "rating": 200,
    "bro": "Success"
}

// string rating
{
    "rating": "200",
    "bro": "Success"
}

Edit: I've found a better swiftier way of implementing init(from decoder: Decoder) throws, which produces a better error message, by using this you can now omit the ParseError enum.

init(from decoder: Decoder) throws {
    let value = try decoder.singleValueContainer()
    do {
        self = .int(try value.decode(Int.self))
    } catch DecodingError.typeMismatch {
        self = .string(try value.decode(String.self))
    }
}

edited May 26 '18 at 09:36

answered May 25 '18 at 10:43

Zonily Jame

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Thank you, that solved my problem!!! – alpha corrado May 25 '18 at 11:19
Upvotes for this guy :D – alpha corrado May 25 '18 at 11:19
@Zonily Jame, how to compare the rating whether its 0 or 1 or 2 or etc with int after using this conversion? i am not able to compare enum with int? thanks – Dhanunjay Kumar Jun 04 '19 at 09:15
Typed Enums have `rawValues` you can start there. – Zonily Jame Jun 06 '19 at 02:14
@Zonily Jame, that is what I need, I meet the same problem today, took me a lot of time. In my case the rating could be object1 or object2 or object3, which three type contain extra many properties ```rating: Movie or TV or Actor```, so how could I work about that? – Zhou Haibo Feb 19 '20 at 17:43
@ChuckZHB You can use enums for this, but for encoding and decoding you have to implement the methods yourself. – Zonily Jame Feb 26 '20 at 08:59
@ZonilyJame after creating the Rating objects how do we segregate the string from the Integers. – Nishad Arora Jul 23 '21 at 12:49
@NishadArora you switch through the cases... – Zonily Jame Jul 27 '21 at 01:49
@ZonilyJame can u kindly elaborate with an example – Nishad Arora Jul 28 '21 at 13:23
@NishadArora https://docs.swift.org/swift-book/LanguageGuide/Enumerations.html – mabarif Jun 22 '22 at 16:01

How to decode a JSON property with different types?

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