Swift decodable json heterogenous array

Question

I have gone through a couple of questions and answers here on SO, and even though they look similar to my question they don't quite address my issue, as I have tried a bunch of them and yet it is not working. Here is my json and the method I have tried and I keep getting an error of "The data couldn’t be read because it isn’t in the correct format."

 {
   "status": 1,
   "errorMsg": "success",
   "data": [
   {
  "id": null,
  "subMenuId": null,
  "type": "Coming Feat",
  "data": {
    "link": "/google.com",
    "title": "Google",
    "shortDescription": "This is fun",
    "imageUrl": "",
    "openInNewWindow": false
  },
  "datas": null,
  "component": null
},
{
  "id": "wdub208t2ghf0b",
  "subMenuId": "39g3hvb83hb98hv",
  "type": "GoingEvent",
  "data": {
    "eventId": "983gv83hv8hv38",
    "sessionId": null,
    "title": "Fest",
    "iconMarker": "http://google.com/sites.png",
    "isPaid": false,
    "startDT": "2018-07-18T16:00:00Z",
    "endDT": "2018-10-31T22:00:00Z",
    "subTitle": null,
    "startDate": "Oct, 2018",
    "endDate": "Oct, 2018",
    "openTime": "04:00 PM",
    "closeTime": "10:00 PM",
    "thumbnail": "https://static.visit.com/estival23.jpg",
    "verticalFeaturedImageUrl": "",
    "horizontalImageUrl": "",
    "categoryTitle": "Celebration",
    "eventCategories": [
      "394bf3w9fbv93v8",
      "dhvbwuehv80"
    ],
    "locations": [
      {
        "uniqueName": "fest",
        "title": "Got if",
        "area": "",
        "region": "Put it",
        "latitude": 67.14517,
        "longitude": 78.797733,
        "distance": "N/A",
        "startDate": "2018-07-18T16:00:00",
        "endDate": "2018-07-27T22:00:00",
        "distancevalue": 0,
        "duration": "N/A",
        "durationValue": 0,
        "valid": true,
        "hasSet": false
      }
    ],
    "prices": null
  },
  "datas": null,
  "component": null
 }
 ]
}

  class FeatureData: Decodable {

var link: String?
var title: String?
var shortDescription: String?
var imageUrl: String?

enum CodingKeys: String, CodingKey {
    case link
    case title
    case shortDescription
    case imageUrl
}

required init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    link = try container.decode(String.self, forKey: .link)
    title = try container.decode(String.self, forKey: .title)
    shortDescription = try container.decode(String.self, forKey: 
  .shortDescription)
    imageUrl = try container.decode(String.self, forKey: .imageUrl)
 }

 init() {
 }
 }


 class FeedFeature: Decodable {

var id: String?
var subMenuId: String?
var type: String?
var data = HomeFeedFeatureData()

enum Codingkeys: String, CodingKey {
    case id
    case subMenuId
    case type
    case data
 }

required init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: Codingkeys.self)
    id = try container.decode(String.self, forKey: .id)
    subMenuId = try container.decode(String.self, forKey: .subMenuId)
    type = try container.decode(String.self, forKey: .type)
    data = try container.decode(HomeFeedFeatureData.self, forKey: 
.data)
}

init() {

 }
 }


   class EventCalendar: Decodable {
// MARK: Properties
var eventId: String = ""
var sessionId: String = ""
var title: String = ""
var iconMarker: String?
var isPaid: Bool = false
var startDT: String = ""
var endDT: String = ""
var subTitle: String = ""
var startDate: String = ""
var endDate: String = ""
var openTime: String = ""
var closeTime: String = ""
var thumbnail: String = ""
var locations: [EventLocation] = []
var prices: [Price]?
var categoryTitle: String = ""

var isLoadingCell: Bool = false
var isSelected: Bool = false

enum CodingKeys: String, CodingKey {
    case eventId = "eventId"
    case sessionId = "sessionId"
    case title = "title"
    case iconMarker = "iconMarker"
    case isPaid = "isPaid"
    case startDT = "startDT"
    case endDT = "endDT"
    case subTitle = "subTitle"
    case startDate = "startDate"
    case endDate = "endDate"
    case openTime = "openTime"
    case closeTime = "closeTime"
    case thumbnail = "thumbnail"
    case locations = "locations"
    case prices = "prices"
    case categoryTitle = "categoryTitle"
  }

init() {}

// MARK: Methods
required init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    eventId = try container.decode(String.self, forKey: .eventId)
    sessionId = try container.decodeIfPresent(String.self, forKey: 
   .sessionId) ?? ""
    title = try container.decodeIfPresent(String.self, forKey: .title) 
     ?? ""
    iconMarker = try container.decodeIfPresent(String.self, forKey: 
  .iconMarker) ?? ""
    isPaid = try container.decodeIfPresent(Bool.self, forKey: .isPaid) 
    ?? false
    startDT = try container.decodeIfPresent(String.self, forKey: 
  .startDT) ?? ""
    endDT = try container.decodeIfPresent(String.self, forKey: .endDT) 
  ?? ""
    subTitle = try container.decodeIfPresent(String.self, forKey: 
.subTitle) ?? ""
    startDate = try container.decodeIfPresent(String.self, forKey: 
.startDate) ?? ""
    endDate = try container.decodeIfPresent(String.self, forKey: 
 .endDate) ?? ""
    openTime = try container.decodeIfPresent(String.self, forKey: 
 .openTime) ?? ""
    closeTime = try container.decodeIfPresent(String.self, forKey: 
.closeTime) ?? ""
    thumbnail = try container.decodeIfPresent(String.self, forKey: 
 .thumbnail) ?? ""
    locations = try container.decodeIfPresent([EventLocation].self, 
 forKey: .locations) ?? []
    categoryTitle = try container.decodeIfPresent(String.self, forKey: 
 .categoryTitle) ?? ""

    // Remove duplicate/invaid prices - The same logic as 
 EventMapComponent
    if let tempPrice = try container.decode([Price]?.self, forKey: 
 .prices) {
        var uniquePrices: [Price] = []
        for price in tempPrice {
            if !uniquePrices.contains(where: { (checkPrice) -> Bool in
                    checkPrice.priceInfo == price.priceInfo &&
                        checkPrice.value == price.value &&
                        checkPrice.currencyCode == price.currencyCode
                }),
                price.priceInfo.count > 0 &&
                    price.value.count > 0 &&
                    price.currencyCode.count > 0 &&
                    price.bookingUrl.count > 0 {

                // Filter for 0 value prices
                if let priceValue = Double(price.value), priceValue > 0 
  {
                    uniquePrices.append(price)
                }
            }
        }
        prices = uniquePrices
    }

    isSelected = BookMarkManager.shared.isFavoriteItem(by: eventId)
 }
 } 

Answer 1

There's a lot wrong with your code. Go through my list below, take it a step at a time, and you'll find that it's a whole lot easier than you're making it

1. Use structs rather than classes where you can (especially if the data is immutable)
2. Use let rather than var, and don't give them initial values.
3. Think carefully about what makes your data valid / invalid. If a value must be there for valid data, make the property non-optional (e.g. if a FeedFeature must have an id to be valid, declare let id: String.
4. If a value might not be there (and the data would still be valid), make the property optional, but don't set it to a default value (e.g. let subTitle: String?)
5. Use the correct type for your properties - startDT is a Date, so declare as let startDT: Date (or Date? if it's optional). You can convert formatted String dates to Date values by setting the dateDecodingStrategy. Use URL rather than String e.g .let thumbnail: URL?,
6. Don't declare CodingKeys when the names all match the properties
7. If you've set up the properties correctly you can remove your own init(from decoder: Decoder) methods.
8. If you remove your Remove duplicate/invalid prices logic from your init - you should be able to do all the above without any code other than the declarations. You can do that after the struct has been initialised (maybe use a temp object for decoding and then copy into another along with the de-duping)

You can easily test this in a playground. Just start with…

let data = """
{your json}
"""".data(using: .utf8)!

struct Response: Decodable {
    let status: Int
    let errorMsg: String
    let data: [FeedFeature]
}

struct FeedFeature: Decodable {
}

JSONDecoder().decode([Response.self], from: data)

and then gradually build up your objects, adding properties one or more at a time.