Convert JSON to Swift objects.



Convert JSON to Swift objects. The Objective-C counterpart can be found here: JSONJoy.

Parsing JSON in Swift has be likened to a trip through Mordor, then JSONJoy would be using eagles for that trip.

First thing is to import the framework. See the Installation instructions on how to add the framework to your project.

import JSONJoy


First here is some example JSON we have to parse.

    "id" : 1,
    "first_name": "John",
    "last_name": "Smith",
    "age": 25,
    "address": {
        "id": 1
        "street_address": "2nd Street",
        "city": "Bakersfield",
        "state": "CA",
        "postal_code": 93309


We want to translate that JSON to these Swift objects:

struct Address {
    let objID: Int?
    let streetAddress: String?
    let city: String?
    let state: String?
    let postalCode: String?
    init() {


struct User {
    let objID: Int?
    let firstName: String?
    let lastName: String?
    let age: Int?
    let address = Address()
    init() {


Normally this would put us in a validation nightmare:

var user = User()
var error: NSError?
var response: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions(), error: &error)
if let userDict = response as? NSDictionary {
    if let addressDict = userDict["address"] as? NSDictionary { = addressDict["city"] as? String
        user.address.streetAddress = addressDict["street_address"] as? String
        //etc, etc
    user.firstName = userDict["first_name"] as? String
    user.lastName = userDict["last_name"] as? String
    //etc, etc

JSONJoy makes this much simpler. We have our Swift objects implement the JSONJoy protocol:

struct Address : JSONJoy {
    let objID: Int
    let streetAddress: String
    let city: String
    let state: String
    let postalCode: String

    init(_ decoder: JSONDecoder) throws {
        objID =         try decoder["id"].get()
        streetAddress = try decoder["street_address"].get()
        city =          try decoder["city"].get()
        state =         try decoder["state"].get()
        postalCode =    try decoder["postal_code"].get()

struct User : JSONJoy {
    let objID: Int
    let firstName: String
    let lastName: String
    let age: Int
    let address: Address

    init(_ decoder: JSONDecoder) throws {
        objID =     try decoder["id"].get()
        firstName = try decoder["first_name"].get()
        lastName =  try decoder["last_name"].get()
        age =       try decoder["age"].get()
        address =   try decoder["address"].get()

Then when we get the JSON back:

do {
    let user = try User(JSONDecoder(data))
    print("city is: \(")
    //That's it! The object has all the appropriate properties mapped.
} catch {
    print("unable to parse the JSON")

This also has automatic optional validation like most Swift JSON libraries.

//some randomly incorrect key. This will work fine and the property will just be nil.
firstName = decoder[5]["wrongKey"]["MoreWrong"].string
//firstName is nil, but no crashing!

Array and Dictionary support

    "addresses": [
        "id": 1
        "street_address": "2nd Street",
        "city": "Bakersfield",
        "state": "CA",
        "postal_code": 93309
        "id": 2
        "street_address": "2nd Street",
        "city": "Dallas",
        "state": "TX",
        "postal_code": 12345
struct Addresses : JSONJoy {
    let addresses: [Address]

    init(_ decoder: JSONDecoder) throws {
        addresses = try decoder["addresses"].get()

Custom Types

If you want to extend JSONJoy to have custom types simple use the rawValue property.

public extension JSONDecoder {
    public var unsignedLong: UInt64? {
        return (rawValue as? NSNumber)?.unsignedLongLongValue

struct SomeStruct : JSONJoy {
    let largeValue: UInt64?
    init(_ decoder: JSONDecoder) throws {
        largeValue = decoder.unsignedLong


This can be combined with SwiftHTTP to make API interaction really clean and easy.


JSONJoy requires at least iOS 7/OSX 10.10 or above.



Check out Get Started tab on

To use JSONJoy-Swift in your project add the following 'Podfile' to your project

source ''
platform :ios, '8.0'

pod 'JSONJoy-Swift', '~> 2.1.0'

Then run:

pod install


Check out the Carthage docs on how to add a install. The JSONJoy framework is already setup with shared schemes.

Carthage Install

You can install Carthage with Homebrew using the following command:

$ brew update
$ brew install carthage

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

github "daltoniam/JSONJoy-Swift" >= 2.1.0


First see the installation docs for how to install Rogue.

To install JSONJoy run the command below in the directory you created the rogue file.

rogue add

Next open the libs folder and add the JSONJoy.xcodeproj to your Xcode project. Once that is complete, in your "Build Phases" add the JSONJoy.framework to your "Link Binary with Libraries" phase. Make sure to add the libs folder to your .gitignore file.


Simply grab the framework (either via git submodule or another package manager).

Add the JSONJoy.xcodeproj to your Xcode project. Once that is complete, in your "Build Phases" add the JSONJoy.framework to your "Link Binary with Libraries" phase.

Add Copy Frameworks Phase

If you are running this in an OSX app or on a physical iOS device you will need to make sure you add the JSONJoy.framework included in your app bundle. To do this, in Xcode, navigate to the target configuration window by clicking on the blue project icon, and selecting the application target under the "Targets" heading in the sidebar. In the tab bar at the top of that window, open the "Build Phases" panel. Expand the "Link Binary with Libraries" group, and add JSONJoy.framework. Click on the + button at the top left of the panel and select "New Copy Files Phase". Rename this new phase to "Copy Frameworks", set the "Destination" to "Frameworks", and add JSONJoy.framework.


  • Complete Docs
  • Add Unit Tests
  • Add Example Project


JSONJoy is licensed under the Apache v2 License.


Dalton Cherry