In the Apple ecosystem, everyone has their own way of implementing a network stack. Many end up with a large `WebService` class where everything gets dumped. These classes, like massive view controllers, expose broad interfaces that are hard to understand, unwieldy to use, and difficult to test. But network stacks don't have to be like this! Let's talk about how you can use the Swish framework to build a protocol-oriented and testable networking stack in Swift that will make you happy. Presented at the Swift Language User Group in SF at Realm. http://www.meetup.com/swift-language/events/232911843/

1. Modern Networking
with Swish
@jakecraige

3. ArgoFunctional JSON parsing library

4. Swish
Nothing but net(working)

5. Setting up a Model with Argo
struct Comment {
let id: Int
let text: String
let user: String
}
extension Comment: Decodable {
// Assume: { "id": 1, "commentText": "Hello world", "user": "ralph" }
static func decode(json: JSON) -> Decoded<Comment> {
return curry(Comment.init)
<^> json <| "id"
<*> json <| "commentText"
<*> json <| "user"
}
}

6. Building a GET Request
struct CommentRequest: Request {
typealias ResponseObject = Comment
let id: Int
func build() -> NSURLRequest {
let url = NSURL(
string: "https://www.example.com/comments/(id)"
)!
return NSURLRequest(URL: url)
}
}

7. Executing the GET Request
let request = CommentRequest(id: 1)
APIClient().performRequest(request) { result in
switch result { // Result<Comment, SwishError>
case let .Success(comment):
print("Here's the comment: (comment)")
case let .Failure(error):
print("Oh no, an error: (error)")
}
}
// => Comment(id: 1, text: "Hi", user: "ralph")

8. GETs are easy.
How about POSTs?

9. Building a POST Request
struct CreateCommentRequest: Request {
typealias ResponseObject = Comment
let text: String
let user: String
var jsonPayload: [String: AnyObject] {
return ["text": text, "user": user]
}
func build() -> NSURLRequest {
// ...
}
}

10. Building a POST Request
struct CreateCommentRequest: Request {
// ...
func build() -> NSURLRequest {
let url = NSURL(string: "https://www.example.com/comments")!
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Accept")
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.jsonPayload = jsonPayload
return request
}
}

11. Executing the POST Request
let request = CreateCommentRequest(text: "Hola", user: "ralph")
APIClient().performRequest(request) { result in
switch result { // Result<Comment, SwishError>
case let .Success(comment):
print("Here's the comment: (value)")
case let .Failure(error):
print("Oh no, an error: (error)")
}
}
// => Comment(id: 2, text: "Hola", user: "ralph")

12. ! "

13. Let's break it down !

14. Argo's Decodable
protocol Decodable {
associatedtype DecodedType = Self
static func decode(_ json: JSON) -> Decoded<DecodedType>
}

15. Argo's Decodable
protocol Decodable {
associatedtype DecodedType = Self
static func decode(_ json: JSON) -> Decoded<DecodedType>
}
extension Comment: Decodable {
static func decode(json: JSON) -> Decoded<Comment> {
return curry(Comment.init)
<^> json <| "id"
<*> json <| "commentText"
<*> json <| "user"
}
}

16. Swish's Request
protocol Parser {
associatedtype Representation
static func parse(j: AnyObject) -> Result<Representation, SwishError>
}
protocol Request {
associatedtype ResponseObject
associatedtype ResponseParser: Parser = JSON
func build() -> NSURLRequest
func parse(j: ResponseParser.Representation)
-> Result<ResponseObject, SwishError>
}

17. Swish's Request
protocol Request {
associatedtype ResponseObject
associatedtype ResponseParser: Parser = JSON
func build() -> NSURLRequest
func parse(j: ResponseParser.Representation) -> Result<ResponseObject, SwishError>
}
struct CommentRequest: Request {
typealias ResponseObject = Comment
let id: Int
func build() -> NSURLRequest {
let url = NSURL(string: "https://www.example.com/comments/(id)")!
return NSURLRequest(URL: url)
}
}

18. Swish Request.parse
struct CommentRequest: Request {
typealias ResponseObject = Comment
let id: Int
func build() -> NSURLRequest {
let url = NSURL(string: "https://www.example.com/comments/(id)")!
return NSURLRequest(URL: url)
}
func parse(j: JSON) -> Result<Comment, SwishError> {
return .fromDecoded(Comment.decode(j)) // Default
return .fromDecoded(j <| "comment") // Root key
}
}

19. Testing

20. Testing Retrieving a Comment
itBehavesLike(.GETRequest, request: CommentRequest(id: 1))
it("points to /comments/:id") {
let request = CommentRequest(id: 1)
expect(request.build()).to(hitEndpoint("/comments/1"))
}

21. Testing Creating a Comment
itBehavesLike(.POSTRequest, request: CreateCommentRequest(text: "", user: ""))
it("points to /comments") {
let request = CreateCommentRequest(text: "", user: "")
expect(request.build()).to(hitEndpoint("/comments"))
}
it("has a payload with the text and user") {
let request = CreateCommentRequest(text: "Hi!", user: "ralph")
expect(request.build()).to(havePayload([
"text": "Hi!",
"user": "ralph"
]))
}

22. Stubbing the Network
it("completes the full request cycle") {
let request = CommentRequest(id: 1)
stub(request).with(.comment)
var response: Comment? = .None
APIClient().performRequest(request) { response = $0.value }
expect(response)
.toEventually(equal(Comment(id: 1, text: "Hallo", user: "ralph")))
}

23. What else can you do
with Swish?

24. What else can you do with Swish?
1. Dependency injection of APIClient, protocol Client, for
testing
2. Cancel in-flight requests
3. Execute requests on different queues.
4. Support arbitrary JSON parsers or response types.
5. Anything you want.

25. Thanks y'all. Questions?
• https://tbot.io/swish-talk
• @jakecraige