The better way to deal with JSON data in Swift


SwiftyJSON 中文介绍

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SwiftyJSON makes it easy to deal with JSON data in Swift.

  1. Why is the typical JSON handling in Swift NOT good
  2. Requirements
  3. Integration
  4. Usage
  5. Work with Alamofire

Why is the typical JSON handling in Swift NOT good?

Swift is very strict about types. But although explicit typing is good for saving us from mistakes, it becomes painful when dealing with JSON and other areas that are, by nature, implicit about types.

Take the Twitter API for example. Say we want to retrieve a user's "name" value of some tweet in Swift (according to Twitter's API

The code would look like this:

if let statusesArray = try? NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments) as? [[String: AnyObject]],
    let user = statusesArray[0]["user"] as? [String: AnyObject],
    let username = user["name"] as? String {
    // Finally we got the username

It's not good.

Even if we use optional chaining, it would be messy:

if let JSONObject = try NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments) as? [[String: AnyObject]],
    let username = (JSONObject[0]["user"] as? [String: AnyObject])?["name"] as? String {
        // There's our username

An unreadable mess--for something that should really be simple!

With SwiftyJSON all you have to do is:

let json = JSON(data: dataFromNetworking)
if let userName = json[0]["user"]["name"].string {
  //Now you got your value

And don't worry about the Optional Wrapping thing. It's done for you automatically.

let json = JSON(data: dataFromNetworking)
if let userName = json[999999]["wrong_key"]["wrong_name"].string {
    //Calm down, take it easy, the ".string" property still produces the correct Optional String type with safety
} else {
    //Print the error


  • iOS 7.0+ / Mac OS X 10.9+
  • Xcode 7


CocoaPods (iOS 8+, OS X 10.9+)

You can use Cocoapods to install SwiftyJSONby adding it to your Podfile:

platform :ios, '8.0'

target 'MyApp' do
    pod 'SwiftyJSON', :git => ''

Note that this requires CocoaPods version 36, and your iOS deployment target to be at least 8.0:

Carthage (iOS 8+, OS X 10.9+)

You can use Carthage to install SwiftyJSON by adding it to your Cartfile:

github "SwiftyJSON/SwiftyJSON"

Swift Package Manager

You can use The Swift Package Manager to install SwiftyJSON by adding the proper description to your Package.swift file:

import PackageDescription

let package = Package(
    name: "YOUR_PROJECT_NAME",
    targets: [],
    dependencies: [
        .Package(url: "", versions: "2.3.3" ..< Version.max)

Note that the Swift Package Manager is still in early design and development, for more infomation checkout it's GitHub Page

Manually (iOS 7+, OS X 10.9+)

To use this library in your project manually you may:

  1. for Projects, just drag SwiftyJSON.swift to the project tree
  2. for Workspaces, include the whole SwiftyJSON.xcodeproj



import SwiftyJSON
let json = JSON(data: dataFromNetworking)
let json = JSON(jsonObject)
if let dataFromString = jsonString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false) {
    let json = JSON(data: dataFromString)


//Getting a double from a JSON Array
let name = json[0].double
//Getting a string from a JSON Dictionary
let name = json["name"].stringValue
//Getting a string using a path to the element
let path = [1,"list",2,"name"]
let name = json[path].string
//Just the same
let name = json[1]["list"][2]["name"].string
let name = json[1,"list",2,"name"].string
//With a hard way
let name = json[].string
//With a custom way
let keys:[SubscriptType] = [1,"list",2,"name"]
let name = json[keys].string


//If json is .Dictionary
for (key,subJson):(String, JSON) in json {
   //Do something you want

The first element is always a String, even if the JSON is an Array

//If json is .Array
//The `index` is 0..<json.count's string value
for (index,subJson):(String, JSON) in json {
    //Do something you want


Use a subscript to get/set a value in an Array or Dictionary

If the JSON is:

  • an array, the app may crash with "index out-of-bounds."
  • a dictionary, it will be assigned nil without a reason.
  • not an array or a dictionary, the app may crash with an "unrecognised selector" exception.

This will never happen in SwiftyJSON.

let json = JSON(["name", "age"])
if let name = json[999].string {
    //Do something you want
} else {
    print(json[999].error) // "Array[999] is out of bounds"
let json = JSON(["name":"Jack", "age": 25])
if let name = json["address"].string {
    //Do something you want
} else {
    print(json["address"].error) // "Dictionary["address"] does not exist"
let json = JSON(12345)
if let age = json[0].string {
    //Do something you want
} else {
    print(json[0])       // "Array[0] failure, It is not an array"
    print(json[0].error) // "Array[0] failure, It is not an array"

if let name = json["name"].string {
    //Do something you want
} else {
    print(json["name"])       // "Dictionary[\"name"] failure, It is not an dictionary"
    print(json["name"].error) // "Dictionary[\"name"] failure, It is not an dictionary"

Optional getter

if let id = json["user"]["favourites_count"].number {
   //Do something you want
} else {
   //Print the error
if let id = json["user"]["name"].string {
   //Do something you want
} else {
   //Print the error
if let id = json["user"]["is_translator"].bool {
   //Do something you want
} else {
   //Print the error
if let id = json["user"]["id"].int {
   //Do something you want
} else {
   //Print the error

Non-optional getter

Non-optional getter is named xxxValue

//If not a Number or nil, return 0
let id: Int = json["id"].intValue
//If not a String or nil, return ""
let name: String = json["name"].stringValue
//If not a Array or nil, return []
let list: Array<JSON> = json["list"].arrayValue
//If not a Dictionary or nil, return [:]
let user: Dictionary<String, JSON> = json["user"].dictionaryValue


json["name"] = JSON("new-name")
json[0] = JSON(1)
json["id"].int =  1234567890
json["coordinate"].double =  8766.766
json["name"].string =  "Jack"
json.arrayObject = [1,2,3,4]
json.dictionary = ["name":"Jack", "age":25]

Raw object

let jsonObject: AnyObject = json.object
if let jsonObject: AnyObject = json.rawValue
//convert the JSON to raw NSData
if let data = json.rawData() {
    //Do something you want
//convert the JSON to a raw String
if let string = json.rawString() {
    //Do something you want


//shows you whether value specified in JSON or not
if json["name"].isExists()

Literal convertibles

For more info about literal convertibles: Swift Literal Convertibles

let json: JSON = "I'm a json"
let json: JSON =  12345
let json: JSON =  true
let json: JSON =  2.8765
let json: JSON =  ["I":"am", "a":"json"]
let json: JSON =  ["I", "am", "a", "json"]
let json: JSON =  nil
//With subscript in array
var json: JSON =  [1,2,3]
json[0] = 100
json[1] = 200
json[2] = 300
json[999] = 300 //Don't worry, nothing will happen
//With subscript in dictionary
var json: JSON =  ["name": "Jack", "age": 25]
json["name"] = "Mike"
json["age"] = "25" //It's OK to set String
json["address"] = "L.A." // Add the "address": "L.A." in json
//Array & Dictionary
var json: JSON =  ["name": "Jack", "age": 25, "list": ["a", "b", "c", ["what": "this"]]]
json["list"][3]["what"] = "that"
json["list",3,"what"] = "that"
let path = ["list",3,"what"]
json[path] = "that"

Work with Alamofire

SwiftyJSON nicely wraps the result of the Alamofire JSON response handler:

Alamofire.request(.GET, url).validate().responseJSON { response in
    switch response.result {
    case .Success:
        if let value = response.result.value {
          let json = JSON(value)
          print("JSON: \(json)")
    case .Failure(let error):