NSURLSession is the main networking API provided by Foundation that allows issuing HTTP requests and handling responses. Popular third party libraries like Alamofire and Moya provide abstractions over NSURLSession to simplify networking code. JSON parsing in Swift requires using third party libraries like Gloss to implement type checking and avoid callback hell when handling JSON responses.

2. CLIENT SERVER
COMMUNICATION

3. AGENDA
NSURLSession
Handling JSON
Third party networking libraries

4. NSURLSESSION

5. NSURLSESSION
Class provided by Foundation library that allows
issuing HTTP requests

6. CANONICAL EXAMPLE
let imageView = UIImageView()
let url = NSURL(string: "http://www.sbs.com.au/news/sites/sbs.com.au.news/files/styles/
full/public/g1369638954952825892.jpg.png?itok=eI4dUGhC&mtime=1429064409")!
let urlRequest = NSURLRequest(URL: url)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(urlRequest) { data, response, error in
if let data = data {
let image = UIImage(data: data)
dispatch_async(dispatch_get_main_queue()) {
imageView.image = image
}
}
}
task.resume()

7. CANONICAL EXAMPLE
1. Retrieve a session from NSURLSession
2. Create a task using that session
3. Provide a delegate or callback to deal with the response

8. NSURLSESSION - TASK TYPES
NSURLSessionDataTask: A task for retrieving the contents
of a URL as an NSData object
NSURLSessionUploadTask: A task for uploading a file,
then retrieving the contents of a URL as an NSData object
NSURLSessionDownloadTask: A task for retrieving the
contents of a URL as a temporary file on disk
Background compatible
Not background compatible!
Source: NSURLSession reference

9. POST EXAMPLE
let content = ["post": "test content"]
let jsonData = try! NSJSONSerialization.dataWithJSONObject(content, options:
NSJSONWritingOptions(rawValue: 0))
let urlPost = NSURL(string: "http://jsonplaceholder.typicode.com/posts")!
let urlRequestPost = NSMutableURLRequest(URL: urlPost)
urlRequestPost.HTTPMethod = "POST"
urlRequestPost.HTTPBody = jsonData
let postTask = session.dataTaskWithRequest(urlRequestPost) { data, response, error in
if let data = data {
print(response)
}
}
postTask.resume()

10. HANDLING JSON

11. HANDLING JSON
Foundation framework provides NSJSONSerialization
Class is poorly suited for Swift 😢

12. HANDLING JSON
let jsonOptional: AnyObject! = NSJSONSerialization.JSONObjectWithData(data,
options: NSJSONReadingOptions(0), error: &jsonErrorOptional)
if let json = jsonOptional as? Dictionary<String, AnyObject> {
if let id = json["id"] as? Int {
if let name = json["name"] as AnyObject? as? String {
if let email = json["email"] as AnyObject? as? String {
let user = User(id: id, name: name, email: email)
callback(user)
}
}
}
}
😢 😢 😢 😢 😢 😢 😢 😢 😢 😢 😢 😢 😢
Source: Efficient JSON in Swift with Functional Concepts and Generics

13. HANDLING JSON
For sane JSON parsing code we need to use third party
libraries that implement type checking for us
There are many libraries available: SwiftyJSON, Argo, Gloss,
etc.

14. HANDLING JSON WITH GLOSSY - 1
struct Post: Glossy {
var title: String?
var content: String?
init?(json: JSON) {
self.title = "title" <~~ json
self.content = "content" <~~ json
}
init(title: String, content: String) {
self.title = title
self.content = content
}
func toJSON() -> JSON? {
return jsonify([
"title" ~~> self.title,
"content" ~~> self.content
])
}
}

15. HANDLING JSON WITH GLOSSY - 2
let jsonPost = Post(title: "Test", content: "Test Content").toJSON()!
let jsonData = try! NSJSONSerialization.dataWithJSONObject(jsonPost, options: NSJSONWritingOptions(rawValue: 0))
let urlPost = NSURL(string: "http://jsonplaceholder.typicode.com/posts")!
let urlRequestPost = NSMutableURLRequest(URL: urlPost)
urlRequestPost.HTTPMethod = "POST"
urlRequestPost.HTTPBody = jsonData
urlRequestPost.setValue("application/json", forHTTPHeaderField: "content-type")
let postTask = session.dataTaskWithRequest(urlRequestPost) { data, response, error in
if let data = data {
let json = try! NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions(rawValue: 0))
let post = Post(json: json as! JSON)
print(post)
}
}
postTask.resume()

16. THIRD PARTY NETWORKING
LIBRARIES

17. THIRD PARTY NETWORKING
Networking code encounters issues that are similar for all
different kinds of apps
Third party libraries help in solving these common problems
(e.g. parsing responses from as server)

18. THIRD PARTY NETWORKING
Alamofire: an abstraction on top of NSURLSession with a
simplified API
Moya: built on top of Alamofire, improves modeling of API
client
Tiny networking: a minimal networking library by Chris
Eidhof, read accompanying blog post

19. SUMMARY

20. SUMMARY
NSURLSession is the main networking API
(Sane) JSON parsing in Swift 2 requires third party
libraries
Popular third party networking libraries provide
abstractions over NSURLSession

21. ADDITIONAL RESOURCES

22. ADDITIONAL RESOURCES
NSURLSession Playground for this talk
NSURLSession class reference
NSURLSession Background Download
URLSession programming guide
Swift JSON Parsing by Example