#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
   • Initialization
   • Subscript
   • Loop
   • Error
   • Optional getter
   • Non-optional getter
   • Setter
   • Raw object
   • Literal convertibles
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(data, options: nil, error: nil)

if let statusesArray = JSONObject as? [AnyObject],
   let status = statusesArray[0] as? [String: AnyObject],
   let user = status["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:

let JSONObject: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: nil, error: nil)

if let username = (((JSONObject as? [AnyObject])?[0] as? [String: AnyObject])?["user"] as? [String: AnyObject])?["name"] as? String {
    // What a disaster
}

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 6.3

##Integration

####CocoaPods (iOS 8+, OS X 10.9+) You can use Cocoapods to install SwiftyJSONby adding it to your Podfile:

platform :ios, '8.0'
use_frameworks!

target 'MyApp' do
    pod 'SwiftyJSON', '~> 2.2.1'
end

Note that it needs you to install CocoaPods 36 version, and requires your iOS deploy target >= 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" >= 2.2.1

####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

Usage

####Initialization

import SwiftyJSON

let json = JSON(data: dataFromNetworking)

let json = JSON(jsonObject)

if let dataFromString = jsonString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false) {
    let json = JSON(data: dataFromString)
}

####Subscript

//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
//Alternatively
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

####Loop

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

####Error 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 get nil without a reason.
• not an array or a dictionary, the app may crash with an "unrecognised selector" exception.

It will never happen in SwiftyJSON.

let json = JSON(["name", "age"])
if 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])
if let name = json["address"].string {
    //Do something you want
} else {
    println(json["address"].error) // "Dictionary["address"] does not exist"
}

let json = JSON(12345)
if 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"
}

if 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.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
}

####Literal convertibles For more info about 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!)
    }
  }