A collection of extensions around the Swift `Codable` implementation.

What's New

CodablePlus 0.4.0


This release adds a few additions:

  • KeyedDecodingContainerProtocol extension to allow for decoding of type Any.
  • KeyedEncodingContainerProtocol extension to allow for encoding of type Any.
  • An AnyEncodable type-erased container that encodes its value to a SingleValueEncodingContainer.


Twitter: @richardpiazza

A collection of extensions around the Swift Codable implementation.


Codable+ is distributed using the Swift Package Manager. To install it into a project, add it as a dependency within your Package.swift manifest:

let package = Package(
    dependencies: [
        .package(url: "", from: "0.3.0")

Then import Codable+ wherever you'd like to use it:

import CodablePlus


Decoding/Encoding Dictionary<String, Any> & Array<Any>

The type Any in Swift does not conform to Codable because it can represent any type (whether codable or not). But, we run into situations where JSON objects are represented by a Dictionary<String, Any>, where Any here is limited to a set of known, codable-supporting types.

Now it's possible to de/serialize JSON objects into/from their swift counterparts. A prime example where this might be used is with API's that may have an expectation of a 'reasonably' defined response, but could userandomor unknown-at-runtime keys. When this is the case, type safety can't be met, but the data is still valuable.

Interacting with the following Container definition and JSON snippet are now possible:

struct Container: Codable {
    var dictionary: [String: Any]

    private enum CodingKeys: String, CodingKey {
        case dictionary

    init(dictionary: [String: Any]) {
        self.dictionary = dictionary

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        dictionary = try container.decode([String: Any].self, forKey: .dictionary)

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(dictionary, forKey: .dictionary)
  "dictionary": {
    "aString": "This is a string.",
    "aInt": 47,
    "aDouble": 55.88,
    "aBool": true,
    "aArray": ["String", 123, 123.456, false],
    "aDictionary": {
      "name": "Bob",
      "age": 69

These same examples can apply to Array<Any> where Any represents one of the JSON compatible primptives:

  • String

  • Int

  • Double

  • Bool

As well as these containers, when composed of the same primitive types.

  • Array

  • Dictionary

Decoding Multiple Keys

During active development of projects, often times an API spec will change, or could possibly be inconsistent from one endpoint to another. It would be handy if our Swift models could be consistent, but support decoding of multiple possible entity models. With Codable+ this is possible.

Given the following:

struct CompanyV1: Decodable {
    var name: String
    var employees: Int

struct CompanyV2: Decodable {
    var companyName: String
    var employees: Int
    var ceoName: String

    private enum CodingKeys: String, CodingKey {
        case name
        case companyName
        case employees
        case ceoName

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        companyName = try container.decode(String.self, forKeys: [.name, .companyName])
        employees = try container.decode(Int.self, forKey: .employees)
        ceoName = try container.decodeIfPresent(String.self, forKey: .ceoName) ?? ""

let schema1json = """
    "name": "Apple",
    "employees": 42000

let schema2json = """
    "companyName": "Microsoft",
    "employees": 600000,
    "ceoName": "Satya Nadella"

Notice the companyName = in the init(from:) method? This specifies multiple CodingKeys as possibilities. Now our CompanyV2 model supports decoding of our CompanyV1 schema.


Codable+ has grown and been inspired by several posts around the interwebs:


  • Swift Tools 5.1.0
View More Packages from this Author


  • None
Last updated: Fri Dec 22 2023 19:03:39 GMT-1000 (Hawaii-Aleutian Standard Time)