Swift 4 Decodable - Additional Variables

Question

Something I havent figured out or have been able to find online as of yet.

Is there a way to add additional fields onto a struct containing the decodable protocol in

Answer 1

To exclude urlImage you must manually conform to Decodable instead of letting its requirements be synthesized:

struct Example1 : Decodable { //(types should be capitalized)
    var name: String?
    var url: URL? //try the `URL` type! it's codable and much better than `String` for storing URLs
    var urlImage: UIImage? //not decoded

    private enum CodingKeys: String, CodingKey { case name, url } //this is usually synthesized, but we have to define it ourselves to exclude `urlImage`
}

Before Swift 4.1 this only works if you add = nil to urlImage, even though the default value of nil is usually assumed for optional properties.

If you want to provide a value for urlImage at initialization, rather than using = nil, you can also manually define the initializer:

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        name = try container.decode(String.self, forKey: .name)
        url = try container.decode(URL.self, forKey: .url)
        urlImage = //whatever you want!
    }