Codable class does not conform to protocol Decodable

Question

Why am I getting a "Type 'Bookmark' does not conform to protocol 'Decodable'" error message?

class Bookmark: Codable {    weak var publication: Publication?    var indexPath: [Int]    var locationInText = 0     enum CodingKeys: String, CodingKey {       case indexPath       case locationInText    }     init(publication: Publication?, indexPath: [Int]) {       self.publication = publication       self.indexPath = indexPath    } } 

I do not wish to save the publication var since the Publication owns the Bookmark but the bookmark needs to know which Publication it belongs to. The decode init of Publication will set the bookmark reference to itself.

Answer 1

The compiler cannot synthesise the required init(from:) method due to the weak reference, so you need to write it yourself.

class Bookmark: Codable {     weak var publication: Publication?     var indexPath: [Int]     var locationInText = 0      private enum CodingKeys: String, CodingKey {         case indexPath         case locationInText     }      init(publication: Publication?, indexPath: [Int]) {         self.publication = publication         self.indexPath = indexPath     }      required init(from decoder:Decoder) throws {         let values = try decoder.container(keyedBy: CodingKeys.self)         indexPath = try values.decode([Int].self, forKey: .indexPath)         locationInText = try values.decode(Int.self, forKey: .locationInText)     } }