I am reading through the Encoding and Decoding Custom Types article, and I am seeing to encoder: Encoder and from decoder: Decoder throughout the examples. I am new to Swift, and it isn't really clear to me why it is to encoder: Encoder and not just encoder: Encoder. Here is a longer snippet for more context: extension Coordinate: Encodable { func encode(to encoder: Encoder) throws { var container = encoder.container(keyedBy: CodingKeys.self) try container.encode(latitude, forKey: .latitude) try container.encode(longitude, forKey: .longitude) var additionalInfo = container.nestedContainer(keyedBy: AdditionalInfoKeys.self, forKey: .additionalInfo) try additionalInfo.encode(elevation, forKey: .elevation) } } What is the purpose of to and from within these examples? I have been trying to find an answer to this question, but searching for "what is the purpose of to in swift" and other variants has been remarkably unsuccessful.

I am wondering if there is a different approach I could take here aside from the nested do { try } catch { do { try } catch { do { try } catch { ... }}}}}} approach I am currently using. Similarly, any comments or suggestions on the switch self { ... } block would be appreciated. UniversalPayload is to encode and decode a JSON payload object which contains three properties op: Int, t: String?, s: Int?, which have a known type and structure, and one property d: JSONAble? which is known to conform to JSON but has an unknown structure otherwise. Will someone please suggest improvements to the following code? struct UniversalPayload: Codable {     typealias GenericPayloadData = [String: PayloadDatum?]          var op: Int     var t: String?     var s: Int?     var d: GenericPayloadData?          enum PayloadDatum: Codable {         case array([PayloadDatum])         case bool(Bool)         case int(Int)         case null(Bool)         case object(GenericPayloadData)         case string(String)                  init(from decoder: Decoder) throws {             let container = try decoder.singleValueContainer()             var value: PayloadDatum?             // Pyramid of do do do do doooom             do { value = try .bool(container.decode(Bool.self)) } catch {                 do { value = try .int(container.decode(Int.self)) } catch {                     do { value = try .string(container.decode(String.self)) } catch {                         do { value = try .array(container.decode([PayloadDatum].self)) } catch {                             do { value = try .object(container.decode(GenericPayloadData.self)) } catch {                                 value = .null(container.decodeNil())                             } // catch .object                         } // catch .array                     } // catch .string                 } // catch .int             } // catch .bool             self = value!         } // init         func encode(to encoder: Encoder) throws {             var container = encoder.singleValueContainer()             switch self {             case .array(let arrayValue):                 try? container.encode(arrayValue)             case .bool(let boolValue):                 try? container.encode(boolValue)             case .int(let intValue):                 try? container.encode(intValue)             case .object(let objectValue):                 try? container.encode(objectValue)             case .string(let stringValue):                 try? container.encode(stringValue)             case .null(let nullValue):                 if nullValue {                     try? container.encodeNil()                 }                 else {                     let context = EncodingError.Context(codingPath: encoder.codingPath,                                                         debugDescription: "Unknown Type")                     throw EncodingError.invalidValue(self, context )                 } // else             } // switch         } // encode     } // PayloadDatum } // UniversalPayload