Swift 4 introduces a new Codable protocol that lets you serialize and deserialize custom data types without writing any special code and without having to worry about losing your value types. 🎉

Awesome, isn't it? And this library helps you write less code! It's an extension for Alamofire that converts JSON data into Decodable object.

Useful Resources:

Encoding and Decoding Custom Types - Article by Apple
Using JSON with Custom Types - Swift Playground
Also there is a special session from WWDC2017 that covers this new feature - What's New in Foundation

Usage

Let's decode a simple json file:

{
    "result": {
        "libraries": [
            {
                "name": "Alamofire",
                "stars": 23857,
                "url": "https://github.com/Alamofire/Alamofire",
                "random_date_commit": 1489276800
            },
            {
                "name": "RxSwift",
                "stars": 9600,
                "url": "https://github.com/ReactiveX/RxSwift",
                "random_date_commit": 1494547200
            }	
        ]
    }
}

with the following Swift model:

private struct Repo: Decodable {
    let name: String
    let stars: Int
    let url: URL
    let randomDateCommit: Date
    
    private enum CodingKeys: String, CodingKey {
        case name
        case stars
        case url
        case randomDateCommit = "random_date_commit"
    }
}

There is a similar method to responseData, responseJSON - responseDecodableObject:

func responseDecodableObject<T: Decodable>(queue: DispatchQueue? = nil, keyPath: String? = nil, decoder: JSONDecoder = JSONDecoder(), completionHandler: @escaping (DataResponse<T>) -> Void)

queue - The queue on which the completion handler is dispatched.
keyPath - The keyPath where object decoding should be performed.
decoder - The decoder that performs the decoding of JSON into semantic Decodable type.

let url = URL(string: "https://raw.githubusercontent.com/otbivnoe/CodableAlamofire/master/keypathArray.json")!
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .secondsSince1970 // It is necessary for correct decoding. Timestamp -> Date.

Alamofire.request(url).responseDecodableObject(keyPath: "result.libraries", decoder: decoder) { (response: DataResponse<[Repo]>) in
    let repo = response.result.value
    print(repo)
}

Note:

For array: DataResponse<[Repo]>
For single object: DataResponse<Repo>

Requirements

Swift 4+
Xcode 9+

Installation 🔥

CocoaPods

CocoaPods is a dependency manager for Swift and Objective-C Cocoa projects. It has over eighteen thousand libraries and can help you scale your projects elegantly. You can install it with the following command:

$ sudo gem install cocoapods

Because of Alamofire supports Swift 3 at the moment and we can't point out the branch of dependency in .podspec file. Whe have to overrride the current pod:

# TODO: Remove this after all pods are converted to swift 4
def swift4_overrides
    pod 'Alamofire', git: 'https://github.com/Alamofire/Alamofire.git', branch: 'swift4'
end

target 'Test' do
  use_frameworks!

  swift4_overrides
  pod 'CodableAlamofire', :git => 'https://github.com/Otbivnoe/CodableAlamofire.git'
  
end

Carthage

NOTE: Don't forget to set the correct Command Line Tools: Xcode > Preferences > Locations > Command Line Tools > Xcode 9.0.

Carthage is a decentralized dependency manager that builds your dependencies and provides you with binary frameworks.

You can install Carthage with Homebrew using the following command:

$ brew update
$ brew install carthage

To integrate CodableAlamofire into your Xcode project using Carthage, specify it in your Cartfile:

github "Otbivnoe/CodableAlamofire"

Run carthage update to build the framework and drag the built CodableAlamofire.framework into your Xcode project.