Dynamic JSON Decoding Swift 4

Question

I\'m trying to decode the following JSON in Swift 4:

{
    \"token\":\"RdJY3RuB4BuFdq8pL36w\",
    \"permission\":\"accounts, users\",
    \"timout_in\":600,         


        

Answer 1

Inspired by @matt comments, here is the full sample I've gone with. I extended the KeyedDecodingContainer to decode the unknown keys and provide a parameter to filter out known CodingKeys.

Sample JSON

{
    "token":"RdJY3RuB4BuFdq8pL36w",
    "permission":"accounts, users",
    "timout_in":600,
    "issuer": "Some Corp",
    "display_name":"John Doe",
    "device_id":"uuid824fd3c3-0f69-4ee1-979a-e8ab25558421"
}

Swift structs

struct AccessInfo : Decodable
{
    let token: String
    let permission: [String]
    let timeout: Int
    let issuer: String
    let additionalData: [String: Any]

    private enum CodingKeys: String, CodingKey
    {
        case token
        case permission
        case timeout = "timeout_in"
        case issuer
    }

    public init(from decoder: Decoder) throws
    {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        token = container.decode(String.self, forKey: .token)
        permission = try container.decode(String.self, forKey: .permission).components(separatedBy: ",")
        timeout = try container.decode(Int.self, forKey: . timeout)
        issuer = container.decode(String.self, forKey: .issuer)

        // Additional data decoding
        let container2 = try decoder.container(keyedBy: AdditionalDataCodingKeys.self)
        self.additionalData = container2. decodeUnknownKeyValues(exclude: CodingKeys.self)
    }
}

private struct AdditionalDataCodingKeys: CodingKey
{
    var stringValue: String
    init?(stringValue: String)
    {
        self.stringValue = stringValue
    }

    var intValue: Int?
    init?(intValue: Int)
    {
        return nil
    }
}

KeyedDecodingContainer Extension

extension KeyedDecodingContainer where Key == AdditionalDataCodingKeys
{
    func decodeUnknownKeyValues(exclude keyedBy: T.Type) -> [String: Any]
    {
        var data = [String: Any]()

        for key in allKeys
        {
            if keyedBy.init(stringValue: key.stringValue) == nil
            {
                if let value = try? decode(String.self, forKey: key)
                {
                    data[key.stringValue] = value
                }
                else if let value = try? decode(Bool.self, forKey: key)
                {
                    data[key.stringValue] = value
                }
                else if let value = try? decode(Int.self, forKey: key)
                {
                    data[key.stringValue] = value
                }
                else if let value = try? decode(Double.self, forKey: key)
                {
                    data[key.stringValue] = value
                }
                else if let value = try? decode(Float.self, forKey: key)
                {
                    data[key.stringValue] = value
                }
                else
                {
                    NSLog("Key %@ type not supported", key.stringValue)
                }
            }
        }

        return data
    }
}

Calling code

let decoder = JSONDecoder()
let accessInfo = try decoder.decode(AccessInfo.self, from: data!)

print("Token: \(accessInfo.token)")
print("Permission: \(accessInfo.permission)")
print("Timeout: \(accessInfo.timeout)")
print("Issuer: \(accessInfo.issuer)")
print("Additional Data: \(accessInfo.additionalData)")

Output

Token: RdJY3RuB4BuFdq8pL36w
Permission: ["accounts", "users"]
Timeout: 600
Issuer: "Some Corp"
Additional Data: ["display_name":"John Doe", "device_id":"uuid824fd3c3-0f69-4ee1-979a-e8ab25558421"]