This my struct
import Foundation
struct Settings: Hashable, Decodable{
var Id = UUID()
var userNotificationId : Int
}
Coding Keys
private enum CodingKeys: String, CodingKey{
**case userNotificationId = "usuarioNotificacionMovilId"** (this is the line that gets me errors)
}
init
init(userNotificationId: Int){
self.userNotificationId = userNotificationId
}
Decoder
init(from decoder: Decoder) throws{
let container = try decoder.container(keyedBy: CodingKeys.self)
userNotificationId = try container.decodeIfPresent(Int.self, forKey: .userNotificationId) ?? 0
}
Encoder
init(from encoder: Encoder) throws{
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(userNotificationId, forKey: .userNotificationId)
}
I get the following error inside the coding method
'self' used before all stored properties are initialized
What is init(from encoder: Encoder) supposed to be? You're not conforming to Encodable, and if you were, you would need to implement func encode(to encoder: Encoder) throws, not another initializer.
That said, your explicit implementation of init(from decoder: Decoder) throws does nothing different from what the compiler would synthesize for you, so it's better to remove it entirely as well.
struct Settings: Hashable, Decodable {
let id = UUID()
let userNotificationId: Int
private enum CodingKeys: String, CodingKey{
case userNotificationId = "usuarioNotificacionMovilId"
}
init(userNotificationId: Int) {
self.userNotificationId = userNotificationId
}
}
is probably all you need.
Related
[Edited to provide a minimal reproducible example ]
This is the complete struct without non relevant vars and functions
InstrumentSet.swift
import Foundation
struct InstrumentsSet: Identifiable, Codable {
private enum CodingKeys: String, CodingKey {
case name = "setName"
case tracks = "instrumentsConfig"
}
var id: String { name }
var name: String
var tracks: [Track]
}
Track.swift
import Foundation
extension InstrumentsSet {
struct Track: Identifiable, Encodable {
private enum TrackKeys: String, CodingKey {
case id = "trackId"
case effects
}
let id: String
var effects: [Effect]?
}
}
extension InstrumentsSet.Track: Decodable {
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: TrackKeys.self)
id = try container.decode(String.self, forKey: .id)
effects = try container.decodeIfPresent([Effect].self, forKey: .effects)
}
}
Effect.swift
import Foundation
import AudioKit
import SoundpipeAudioKit
extension InstrumentsSet.Track {
enum Effect: Decodable {
private enum EffectKeys: String, CodingKey {
case effectType = "effectName"
case cutoffFrequency
case resonance
}
case lowPassFilter(LowPassFilterEffect)
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: EffectKeys.self)
let effectType = try container.decode(Effect.EffectType.self, forKey: .effectType)
switch effectType {
case .lowPassFilter:
let cutOffFrequency = try container.decode(ValueAndRange.self, forKey: .cutoffFrequency)
let resonance = try container.decode(ValueAndRange.self, forKey: .resonance)
self = .lowPassFilter(LowPassFilterEffect(cutOffFrequency: cutOffFrequency, resonance: resonance))
default:
fatalError("Not implemented!")
}
}
}
}
extension InstrumentsSet.Track.Effect {
enum EffectType: String, Decodable {
case lowPassFilter
}
}
extension InstrumentsSet.Track.Effect: Encodable {
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: EffectKeys.self)
//FIXME: This is the location of the error: Type 'ValueAndRange.Type' cannot conform to 'Encodable'
try container.encode(ValueAndRange.self, forKey: .cutoffFrequency)
}
}
The problem is ValueAndRange.self not not conforming to Encodable
I've followed multiple examples to get to this implementation:
import Foundation
import AudioKit
struct ValueAndRange: Encodable {
private enum ValueRangeKeys: String, CodingKey {
case value
case range
}
static var zero: ValueAndRange { .init(value: 0, range: [0, 0]) }
var value: AUValue
var range: [Double]
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: ValueRangeKeys.self)
try container.encode(value, forKey: .value)
try container.encode(range, forKey: .range)
}
}
extension ValueAndRange: Decodable {
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: ValueRangeKeys.self)
value = try container.decode(AUValue.self, forKey: .value)
range = try container.decode([Double].self, forKey: .range)
}
}
I cannot see why this struct should not conform to Encodable. Maybe any of you got betters eyes (and brains) then I got?
Your encode function is incorrectly trying to encode a type, ValueAndRange.self, rather than a value.
Looking at the init(from:) method I think your encode function should look something like this
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: EffectKeys.self)
switch self {
case .lowPassFilter(let effect):
try container.encode(effect.cutOffFrequency, forKey: .cutoffFrequency)
try container.encode(effect.resonance, forKey: .resonance)
}
}
I didn't include .effectType in this code since I am uncertain of its usage (isn't it always the same hard coded string?).
How does one add Codable conformance to a class that needs to be isolated to the MainActor?
For example, the following code gives compiler errors:
#MainActor final class MyClass: Codable {
var value: Int
enum CodingKeys: String, CodingKey {
case value
}
init(from decoder: Decoder) throws { // <-- Compiler error: Initializer 'init(from:)' isolated to global actor 'MainActor' can not satisfy corresponding requirement from protocol 'Decodable'
let data = try decoder.container(keyedBy: CodingKeys.self)
self.value = try data.decode(Int.self, forKey: .value)
}
func encode(to encoder: Encoder) throws { // <-- Compiler error: Instance method 'encode(to:)' isolated to global actor 'MainActor' can not satisfy corresponding requirement from protocol 'Encodable'
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(value, forKey: .value)
}
}
I'm definitely struggling to get my head around actors and #MainActor at the moment!
There isn't anything about the class you've provided that needs to be isolated to the main actor, so don't isolate the class as a whole. If there are other members that you have not shown us that do need to be isolated to the main actor, isolate them.
Example:
final class MyClass: Codable {
private var value: Int
#MainActor init(value: Int) {
self.value = value
}
#MainActor func setMyValue(to newValue:Int) {
self.value = newValue
}
#MainActor func getMyValue() -> Int {
self.value
}
enum CodingKeys: String, CodingKey {
case value
}
init(from decoder: Decoder) throws {
let data = try decoder.container(keyedBy: CodingKeys.self)
self.value = try data.decode(Int.self, forKey: .value)
}
func encode(to encoder: Encoder) throws { // <-- Compiler error: Instance method 'encode(to:)' isolated to global actor 'MainActor' can not satisfy corresponding requirement from protocol 'Encodable'
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(value, forKey: .value)
}
}
Trying to make this class codable and decodable
import Foundation
class Attribute : Decodable {
struct Att: Decodable {
var number: Int16
var label: String
var comments: String
// Everything from here on is generated for you by the compiler
init(from decoder: Decoder) throws {
let keyedContainer = try decoder.container(keyedBy: CodingKeys.self)
number = try keyedContainer.decode(Int16.self, forKey: .number)
label = try keyedContainer.decode(String.self, forKey: .label)
comments = try keyedContainer.decode(String.self, forKey: .comments)
}
enum CodingKeys: String, CodingKey {
case number
case label
case comments
}
}
}
extension Attribute: Encodable {
public func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(number, forKey: .number)
try container.encode(label, forKey: .label)
try container.encode(comments, forKey: .comments)
}
}
I have an error on these lines
try container.encode(number, forKey: .number)
try container.encode(label, forKey: .label)
try container.encode(comments, forKey: .comments)
with the message
Use of unresolved identifier 'number'
Use of unresolved identifier 'label'
Use of unresolved identifier 'comments'
How do I solve that?
Why do you have an empty class with a nested struct in it? The error comes from the fact that those properties are defined on Att rather than Attribute, so you need to encode those when extending Att to conform to Encodable.
Btw, you don't have any special encoding/decoding, so you don't need to declare the encoder/decoder functions manually, the compiler can synthesise them for you.
class Attribute: Codable {
struct Att: Codable {
var number: Int16
var label: String
var comments: String
}
}
I may have missed something, but the following should work, or at least compile:
class Attribute : Decodable {
var number: Int16
var label: String
var comments: String
// Everything from here on is generated for you by the compiler
required init(from decoder: Decoder) throws {
Is it possible to extend NSDecimalNumber to conform Encodable & Decodable protocols?
It is not possible to extend NSDecimalNumber to conform to Encodable & Decodable protocols. Jordan Rose explains it in the following swift evolution email thread.
If you need NSDecimalValue type in your API you can build computed property around Decimal.
struct YourType: Codable {
var decimalNumber: NSDecimalNumber {
get { return NSDecimalNumber(decimal: decimalValue) }
set { decimalValue = newValue.decimalValue }
}
private var decimalValue: Decimal
}
Btw. If you are using NSNumberFormatter for parsing, beware of a known bug that causes precision loss in some cases.
let f = NumberFormatter()
f.generatesDecimalNumbers = true
f.locale = Locale(identifier: "en_US_POSIX")
let z = f.number(from: "8.3")!
// z.decimalValue._exponent is not -1
// z.decimalValue._mantissa is not (83, 0, 0, 0, 0, 0, 0, 0)
Parse strings this way instead:
NSDecimalNumber(string: "8.3", locale: Locale(identifier: "en_US_POSIX"))
In swift you should use Decimal type. This type confirms to protocols Encodable & Decodable from the box.
If you have NSDecimalNumber type in your code it's easy to cast it to Decimal
let objcDecimal = NSDecimalNumber(decimal: 10)
let swiftDecimal = (objcDecimal as Decimal)
With Swift 5.1 you can use property wrappers to avoid the boilerplate of writing a custom init(from decoder: Decoder) / encode(to encoder: Encoder).
#propertyWrapper
struct NumberString {
private let value: String
var wrappedValue: NSDecimalNumber
init(wrappedValue: NSDecimalNumber) {
self.wrappedValue = wrappedValue
value = wrappedValue.stringValue
}
}
extension NumberString: Decodable {
init(from decoder: Decoder) throws {
value = try String(from: decoder)
wrappedValue = NSDecimalNumber(string: value)
}
}
extension NumberString: Encodable {
func encode(to encoder: Encoder) throws {
var container = encoder.singleValueContainer()
try container.encode(wrappedValue.stringValue)
}
}
extension NumberString: Equatable {}
Usage:
struct Foo: Codable {
#NumberString var value: NSDecimalNumber
}
In my case, We are maintaining legacy code which is Objective-C and Swift
One of the modules we needed to have a property of type NSNumber (internal API reason) which is not supported by Codable
So We use Codable for almost all supported data types and NSCoding with a help of NSKeyedUnarchiver for unsupported types
I am sharing here a sample of the code, as a reference that might help
someone who has a such scenario.
class Branch: NSObject, Codable {
#objc var discountMaxLimit: NSNumber?
private enum CodingKeys: String, CodingKey {
case discountInfoKeys
}
private enum CorporateDiscountInfoKeys: String, CodingKey {
case discountMaxLimit = "discount_max_limit"
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
var discountInfoK = container.nestedContainer(keyedBy: discountInfoKeys.self, forKey: .discountInfoKeys)
if let value = discountMaxLimit {
let data = try NSKeyedArchiver.archivedData(withRootObject: value, requiringSecureCoding: false)
try discountInfoK.encode(data, forKey: .discountMaxLimit)
}
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
let discountInfo = try container.nestedContainer(keyedBy: discountInfoKeys.self, forKey: .discountInfoKeys)
let discountMaxLimitData = try discountInfo.decode(Data.self, forKey: .discountMaxLimit)
discountMaxLimit = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(discountMaxLimitData) as? NSNumber
}
}
Should the use of class inheritance break the Decodability of class. For example, the following code
class Server : Codable {
var id : Int?
}
class Development : Server {
var name : String?
var userId : Int?
}
var json = "{\"id\" : 1,\"name\" : \"Large Building Development\"}"
let jsonDecoder = JSONDecoder()
let item = try jsonDecoder.decode(Development.self, from:json.data(using: .utf8)!) as Development
print(item.id ?? "id is nil")
print(item.name ?? "name is nil") here
output is:
1
name is nil
Now if I reverse this, name decodes but id does not.
class Server {
var id : Int?
}
class Development : Server, Codable {
var name : String?
var userId : Int?
}
var json = "{\"id\" : 1,\"name\" : \"Large Building Development\"}"
let jsonDecoder = JSONDecoder()
let item = try jsonDecoder.decode(Development.self, from:json.data(using: .utf8)!) as Development
print(item.id ?? "id is nil")
print(item.name ?? "name is nil")
output is:
id is nil
Large Building Development
And you can't express Codable in both classes.
I believe in the case of inheritance you must implement Coding yourself. That is, you must specify CodingKeys and implement init(from:) and encode(to:) in both superclass and subclass. Per the WWDC video (around 49:28, pictured below), you must call super with the super encoder/decoder.
required init(from decoder: Decoder) throws {
// Get our container for this subclass' coding keys
let container = try decoder.container(keyedBy: CodingKeys.self)
myVar = try container.decode(MyType.self, forKey: .myVar)
// otherVar = ...
// Get superDecoder for superclass and call super.init(from:) with it
let superDecoder = try container.superDecoder()
try super.init(from: superDecoder)
}
The video seems to stop short of showing the encoding side (but it's container.superEncoder() for the encode(to:) side) but it works in much the same way in your encode(to:) implementation. I can confirm this works in this simple case (see playground code below).
I'm still struggling with some odd behavior myself with a much more complex model I'm converting from NSCoding, which has lots of newly-nested types (including struct and enum) that's exhibiting this unexpected nil behavior and "shouldn't be". Just be aware there may be edge cases that involve nested types.
Edit: Nested types seem to work fine in my test playground; I now suspect something wrong with self-referencing classes (think children of tree nodes) with a collection of itself that also contains instances of that class' various subclasses. A test of a simple self-referencing class decodes fine (that is, no subclasses) so I'm now focusing my efforts on why the subclasses case fails.
Update June 25 '17: I ended up filing a bug with Apple about this. rdar://32911973 - Unfortunately an encode/decode cycle of an array of Superclass that contains Subclass: Superclass elements will result in all elements in the array being decoded as Superclass (the subclass' init(from:) is never called, resulting in data loss or worse).
//: Fully-Implemented Inheritance
class FullSuper: Codable {
var id: UUID?
init() {}
private enum CodingKeys: String, CodingKey { case id }
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
id = try container.decode(UUID.self, forKey: .id)
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(id, forKey: .id)
}
}
class FullSub: FullSuper {
var string: String?
private enum CodingKeys: String, CodingKey { case string }
override init() { super.init() }
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
let superdecoder = try container.superDecoder()
try super.init(from: superdecoder)
string = try container.decode(String.self, forKey: .string)
}
override func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(string, forKey: .string)
let superencoder = container.superEncoder()
try super.encode(to: superencoder)
}
}
let fullSub = FullSub()
fullSub.id = UUID()
fullSub.string = "FullSub"
let fullEncoder = PropertyListEncoder()
let fullData = try fullEncoder.encode(fullSub)
let fullDecoder = PropertyListDecoder()
let fullSubDecoded: FullSub = try fullDecoder.decode(FullSub.self, from: fullData)
Both the super- and subclass properties are restored in fullSubDecoded.
Found This Link - Go down to inheritance section
override func encode(to encoder: Encoder) throws {
try super.encode(to: encoder)
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(employeeID, forKey: .employeeID)
}
For Decoding I did this:
required init(from decoder: Decoder) throws {
try super.init(from: decoder)
let values = try decoder.container(keyedBy: CodingKeys.self)
total = try values.decode(Int.self, forKey: .total)
}
private enum CodingKeys: String, CodingKey
{
case total
}
🚀 Swift introduced Property Wrappers in 5.1 I implemented a library called SerializedSwift that uses the power of property wrappers to Decode and Encode JSON data to objects.
One of my main goals was, to make inherited object to decode out of the box, without additonal init(from decoder: Decoder) overrides.
import SerializedSwift
class User: Serializable {
#Serialized
var name: String
#Serialized("globalId")
var id: String?
#Serialized(alternateKey: "mobileNumber")
var phoneNumber: String?
#Serialized(default: 0)
var score: Int
required init() {}
}
// Inherited object
class PowerUser: User {
#Serialized
var powerName: String?
#Serialized(default: 0)
var credit: Int
}
It also supports custom coding keys, alternate keys, default values, custom transformation classes and many more features to be included in the future.
Available on GitHub (SerializedSwift).
I was able to make it work by making my base class and subclasses conform to Decodable instead of Codable. If I used Codable it would crash in odd ways, such as getting a EXC_BAD_ACCESS when accessing a field of the subclass, yet the debugger could display all the subclass values with no problem.
Additionally, passing the superDecoder to the base class in super.init() didn't work. I just passed the decoder from the subclass to the base class.
How about using the following way?
protocol Parent: Codable {
var inheritedProp: Int? {get set}
}
struct Child: Parent {
var inheritedProp: Int?
var title: String?
enum CodingKeys: String, CodingKey {
case inheritedProp = "inherited_prop"
case title = "short_title"
}
}
Additional info on composition: http://mikebuss.com/2016/01/10/interfaces-vs-inheritance/
Here is a library TypePreservingCodingAdapter to do just that (can be installed with Cocoapods or SwiftPackageManager).
The code below compiles and works just fine with Swift 4.2. Unfortunately for every subclass you'll need to implement encoding and decoding of properties on your own.
import TypePreservingCodingAdapter
import Foundation
// redeclared your types with initializers
class Server: Codable {
var id: Int?
init(id: Int?) {
self.id = id
}
}
class Development: Server {
var name: String?
var userId: Int?
private enum CodingKeys: String, CodingKey {
case name
case userId
}
init(id: Int?, name: String?, userId: Int?) {
self.name = name
self.userId = userId
super.init(id: id)
}
required init(from decoder: Decoder) throws {
try super.init(from: decoder)
let container = try decoder.container(keyedBy: CodingKeys.self)
name = try container.decodeIfPresent(String.self, forKey: .name)
userId = try container.decodeIfPresent(Int.self, forKey: .userId)
}
override func encode(to encoder: Encoder) throws {
try super.encode(to: encoder)
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(name, forKey: .name)
try container.encode(userId, forKey: .userId)
}
}
// create and adapter
let adapter = TypePreservingCodingAdapter()
let encoder = JSONEncoder()
let decoder = JSONDecoder()
// inject it into encoder and decoder
encoder.userInfo[.typePreservingAdapter] = adapter
decoder.userInfo[.typePreservingAdapter] = adapter
// register your types with adapter
adapter.register(type: Server.self).register(type: Development.self)
let server = Server(id: 1)
let development = Development(id: 2, name: "dev", userId: 42)
let servers: [Server] = [server, development]
// wrap specific object with Wrap helper object
let data = try! encoder.encode(servers.map { Wrap(wrapped: $0) })
// decode object back and unwrap them force casting to a common ancestor type
let decodedServers = try! decoder.decode([Wrap].self, from: data).map { $0.wrapped as! Server }
// check that decoded object are of correct types
print(decodedServers.first is Server) // prints true
print(decodedServers.last is Development) // prints true
Swift 5
The compiler synthesises decodable code only for a type that directly adopts Codable protocol so that you observe decoding for a single of your type in inheritance.
But you can try next generic approach with KeyValueCoding package (https://github.com/ikhvorost/KeyValueCoding) and this package provides access to all properties metadata and allows to get/set any property for pure swift types dynamically. The idea is to make a base Coding class which adopts KeyValueCoding and implements decoding of all available properties in init(from: Decoder):
class Coding: KeyValueCoding, Decodable {
typealias DecodeFunc = (KeyedDecodingContainer<_CodingKey>, _CodingKey) throws -> Any?
struct _CodingKey: CodingKey {
let stringValue: String
let intValue: Int?
init(stringValue: String) {
self.stringValue = stringValue
self.intValue = Int(stringValue)
}
init(intValue: Int) {
self.stringValue = "\(intValue)"
self.intValue = intValue
}
}
static func decodeType<T: Decodable>(_: T.Type) -> (type: T.Type, f: DecodeFunc) {
(T.self, { try $0.decode(T.self, forKey: $1) })
}
static var decodeTypes: [(Any.Type, DecodeFunc)] = [
decodeType(Int.self),
decodeType(Int?.self),
decodeType(String.self),
decodeType(String?.self),
// Other types to support...
]
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: _CodingKey.self)
try container.allKeys.forEach { codingKey in
let key = codingKey.stringValue
guard let property = (properties.first { $0.name == key }),
let item = (Self.decodeTypes.first { property.type == $0.0 })
else {
return
}
var this = self
this[key] = try item.1(container, codingKey)
}
}
}
It is important to provide all supported types to decode in decodeTypes variable.
How to use:
class Server: Coding {
var id: Int?
}
class Development : Server {
var name: String = ""
}
class User: Development {
var userId: Int = 0
}
func decode() {
let json = "{\"id\": 1, \"name\": \"Large Building Development\", \"userId\": 123}"
do {
let user = try JSONDecoder().decode(User.self, from:json.data(using: .utf8)!)
print(user.id, user.name, user.userId) // Optional(1) Large Building Development 123
}
catch {
print(error.localizedDescription)
}
}