Latest 0.2.1
License MIT
Platforms ios 9.0



CodableExtensions is available through CocoaPods. To install
it, simply add the following line to your Podfile:

pod 'CodableExtensions'

and run

pod install


Custom Transformations


To make a custom decoding transformer, you just need to implement DecodingContainerTransformer
An example is provided in the project for converting a Regex

import CodableExtensions

public class RegexCodableTransformer: DecodingContainerTransformer {

    public typealias Input = String
    public typealias Output = NSRegularExpression

    public init() {}

    public func transform(_ decoded: Input) throws -> Output {
        return try NSRegularExpression(pattern: decoded, options: [])

The Input and Output types need defining to match the type you expect to be converting from and to, in this case the input is a String and the output is an NSRegularExpression.

The logic to perfrom the transformation is then performed in the transform function. If there’s an error at any point then that needs to be thrown.

The custom transformer can then be used in the Decodable initialiser

init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        regex = try container.decode(.regex, transformer: RegexCodableTransformer())

To make a custom encoding transformer, make a class implementing EncodingContainerTransformer

Example encoding an NSRegularExpression

class RegexCodableTransformer: EncodingContainerTransformer {

    typealias Input = String
    typealias Output = NSRegularExpression

    public func transform(_ encoded: Output) throws -> Input {
        return encoded.pattern

and to use this transformer implement the Encodable function encode(to encoder: Encoder)

func encode(to encoder: Encoder) throws {
        var container =  encoder.container(keyedBy: CodingKeys.self)
        try container.encode(regex, forKey: .regex, transformer: RegexCodableTransformer())

If your transformer conforms to both the EncodingContainerTransformer and DecodingContainerTransformer you can use the CodingContainerTransformer typealias

For full examples check out the tests

For a writeup on the motivation behind this library check my Medium article out



CodableExtensions is available under the MIT license. See the LICENSE file for more info.

Latest podspec

    "name": "CodableExtensions",
    "version": "0.2.1",
    "summary": "CodableExtensions provides some useful extensions to Swift Codable",
    "description": "Adds extensions to allow custom transformations during decoding. Also makes the interface a bit cleaner.",
    "homepage": "",
    "license": {
        "type": "MIT",
        "file": "LICENSE"
    "authors": {
        "jamesruston": "[email protected]"
    "source": {
        "git": "",
        "tag": "0.2.1"
    "social_media_url": "",
    "platforms": {
        "ios": "9.0"
    "source_files": "Classes/**/*",
    "pushed_with_swift_version": "3.0"

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