Handling Swift JSONDecoder typeMismatch error while using Codable protocol

If you have a problematic JSON, which can contain number or string for some keys, you can decode object without that property and manually set that property after decoding.

For example, I have a Vehicle class inside HistoryItem. In Vehicle model_year can be empty String or non empty Int. Here I am decoding modelYear manually using NSDictionary and trying to get Int. Swift 4 cannot do it automatically.

    do {
        // Decoding HistoryItem from JSON
        let jsonData = try JSONSerialization.data(withJSONObject: dict, options: .prettyPrinted)
        let decoder = JSONDecoder()
        let historyItem = try decoder.decode(HistoryItem.self, from: jsonData)
        if let modelYear = (dict as NSDictionary).value(forKeyPath: "vehicle.model_year") as? Int {
            historyItem.vehicle?.modelYear = modelYear
        }
        
        // Saving HistoryItem to Realm
        let realm = try! Realm()
        try! realm.write {
            realm.add(historyItem, update: true)
        }
        
    } catch {
        print(error.localizedDescription)
    }

This is my Vehicle class that is contained inside HistoryItem:

    class Vehicle: Object, Codable {
        @objc dynamic var VIN: String = ""
        @objc dynamic var make: String?
        @objc dynamic var modelName: String?
        @objc dynamic var recallCount: Int = 0
        @objc dynamic var modelYear: Int = 0
        
        override static func primaryKey() -> String? {
            return "VIN"
        }
        
        private enum CodingKeys: String, CodingKey {
            case VIN = "vin"
            case make
            case modelName = "model_name"
            case recallCount = "recall_count"
        }
    }

As you see, there is no model_year key in CodingKeys.