The better way to deal with JSON data in Swift
Swift C++ Ruby
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README.md

#SwiftyJSON 中文介绍

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 https://dev.twitter.com/docs/api/1.1/get/statuses/home_timeline).

The code would look like this:

let jsonObject : AnyObject! = NSJSONSerialization.JSONObjectWithData(dataFromTwitter, options: NSJSONReadingOptions.MutableContainers, error: nil)
if let statusesArray = jsonObject as? NSArray{
    if let aStatus = statusesArray[0] as? NSDictionary{
        if let user = aStatus["user"] as? NSDictionary{
            if let userName = user["name"] as? NSDictionary{
                //Finally We Got The Name
                
            }
        }
    }
}

It's not good.

Even if we use optional chaining, it would also cause a mess:

let jsonObject : AnyObject! = NSJSONSerialization.JSONObjectWithData(dataFromTwitter, options: NSJSONReadingOptions.MutableContainers, error: nil)
if let userName = (((jsonObject as? NSArray)?[0] as? NSDictionary)?["user"] as? NSDictionary)?["name"]{
  //What A disaster above
}

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
    println(json[999999]["wrong_key"]["wrong_name"])
}

Requirements

  • iOS 7.0+ / Mac OS X 10.9+
  • Xcode 6.1

##Integration

You can use Carthage to install SwiftyJSON by adding github "SwiftyJSON/SwiftyJSON" >= 2.1.2 to your Cartfile

CocoaPods is now supported for Swift yet. But to use this library in your project manually you should:

  1. for Projects just drag SwiftyJSON.swift to the project tree
  2. for Workspaces you may include the whole SwiftyJSON.xcodeproj as suggested by @garnett

Usage

####Initialization

let json = JSON(data: dataFromNetworking)
let json = JSON(jsonObject)

####Subscript

//With a int from JSON supposed to an Array
let name = json[0].double
//With a string from JSON supposed to an Dictionary
let name = json["name"].stringValue
//With an array like 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
//With a literal array to the element
let name = json[1,"list",2,"name"].string 
//Just the same
let name = json[1]["list"][2]["name"].string
//With a Hard Way
let name = json[[1,"list",2,"name"]].string

####Loop

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

The first element is always String, even if the JSON's object is Array

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

####Error Use subscript to get/set value in Array or Dicitonary

  • If json is an array, the app may crash with "index out-of-bounds."
  • If json is a dictionary, it will get nil without the reason.
  • If json is not an array or a dictionary, the app may crash with the wrong selector exception.

It will never happen in SwiftyJSON

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

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

####Optional getter

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

####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

####Setter

json["name"] = JSON("new-name")
json[0] = JSON(1)
json["id"].int =  1234567890
json["coordinate"].double =  8766.766
json["name"].string =  "Jack"
json.array = [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 raw String
if let string = json.rawString() {
    //Do something you want
}

####Literal convertibles More info about the literal convertibles: Swift Literal Convertibles

//StringLiteralConvertible
let json:JSON = "I'm a json"
//IntegerLiteralConvertible
let json:JSON =  12345
//BooleanLiteralConvertible
let json:JSON =  true
//FloatLiteralConvertible
let json:JSON =  2.8765
//DictionaryLiteralConvertible
let json:JSON =  ["I":"am", "a":"json"]
//ArrayLiteralConvertible
let json:JSON =  ["I", "am", "a", "json"]
//NilLiteralConvertible
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, parameters: parameters)
  .responseJSON { (req, res, json, error) in
    if(error != nil) {
      NSLog("Error: \(error)")
      println(req)
      println(res)
    }
    else {
      NSLog("Success: \(url)")
      var json = JSON(json!)
    }
  }