Taming Asynchronous Transforms with Interstellar
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The document introduces concepts of functional programming and error handling in asynchronous programming using a Unix-like pipeline analogy. It covers optional types, signal management, and practical examples of how to implement these concepts in programming. The content emphasizes the transition from traditional data handling to a more reactive approach, with a focus on signals and threading in a user interface context.
![func double(i: Int) -> [Int] { return [i, 2*i] }
[1, 2, 3].map(double) // [[1,2], [2,4], [3,6]]
[1, 2, 3].flatMap(double) // [[1, 2, 2,4, 3,6]](https://image.slidesharecdn.com/interstellar-async-151201092703-lva1-app6891/85/Taming-Asynchronous-Transforms-with-Interstellar-12-320.jpg)
![func ls()-> Result<[String]>
func grep(pattern: String)(values: [String]) -> [String]
func sort(values: [String]) -> [String] { return [] }
let sorted = ls().map(grep("*.jpg")).map(sort)
ls | grep *.jpg | sort](https://image.slidesharecdn.com/interstellar-async-151201092703-lva1-app6891/85/Taming-Asynchronous-Transforms-with-Interstellar-17-320.jpg)
![func poll() -> Signal<[Conversation]> {
let signal = Signal<[Conversation]>()
let json = api
.executeRequest(.GetConversations)
.map { $0.json }
let conversations = json
.flatMap(Sync<Conversation>(context: context).updateObjects)
let messages = json
.flatMap(getMessages)
.flatMap(Sync<Message>(context: context).updateObjects)
conversations.merge(messages)
.flatMap(context.saveAndPipe)
.next { signal.update($0.0) }
.error { signal.update($0) }
signal.map(countUnread).next(setUnreadCount)
return signal
}](https://image.slidesharecdn.com/interstellar-async-151201092703-lva1-app6891/85/Taming-Asynchronous-Transforms-with-Interstellar-29-320.jpg)
![func poll() -> Signal<[Conversation]> {
let signal = Signal<[Conversation]>()
let json = api
.executeRequest(.GetConversations)
.map { $0.json }
let conversations = json
.flatMap(Sync<Conversation>(context: context).updateObjects)
let messages = json
.flatMap(getMessages)
.flatMap(Sync<Message>(context: context).updateObjects)
conversations.merge(messages)
.flatMap(context.saveAndPipe)
.next { signal.update($0.0) }
.error { signal.update($0) }
signal.map(countUnread).next(setUnreadCount)
return signal
}
API Request
sync conversations
sync messages
wait for both
then save
update unread
count
notify listeners](https://image.slidesharecdn.com/interstellar-async-151201092703-lva1-app6891/85/Taming-Asynchronous-Transforms-with-Interstellar-30-320.jpg)
Taming Asynchronous Transforms with Interstellar
- 2. let me = Person(name: "Jens Ravens", company: "nerdgeschoss") @JensRavens GitHub: JensRavens jensravens.com nerdgeschoss.de
- 3. A short introduction to functional programming, the universe and everything.
- 4. In the beginning McIlroy created the unix pipe. And he saw it was good. ls | grep *.jpg | sort
- 6. Optionals are a box containing something.
- 7. struct Cat { func pet() -> String { return "purrr" } } let boxContainingCat: Optional<Cat> = Cat() let sound: String? if let cat = boxContainingCat { sound = cat.pet() } else { sound = nil }
- 8. struct Cat { func pet() -> String { return "purrr" } } let boxContainingCat: Optional<Cat> = Cat() let sound = boxContainingCat?.pet()
- 9. struct Cat { func pet() -> String { return "purrr" } } let boxContainingCat: Optional<Cat> = Cat() let sound = boxContainingCat.map { cat in cat.pet() }
- 10. struct Cat { func pet() -> String? { return "purrr" } } let boxContainingCat: Optional<Cat> = Cat() let sound: String?? = boxContainingCat.map { cat in cat.pet() }
- 11. struct Cat { func pet() -> String? { return "purrr" } } let boxContainingCat: Optional<Cat> = Cat() let sound: String? = boxContainingCat.flatMap { cat in cat.pet() }
- 12. func double(i: Int) -> [Int] { return [i, 2*i] } [1, 2, 3].map(double) // [[1,2], [2,4], [3,6]] [1, 2, 3].flatMap(double) // [[1, 2, 2,4, 3,6]
- 13. Error Handling
- 14. Buy it, use it, break it, fix it, Trash it, change it, mail - upgrade it. – Daft Punk, Technologic
- 15. Buy it; if error { //TODO: Handle me! } else { use it; if error { //TODO: Handle me! } else { break it; if error { //TODO: Handle me!
- 16. enum Result<T> { case Success(T) case Error(ErrorType) func map<U>(f: T -> U) -> Result<U> func flatMap<U>(f: T -> Result<U>) -> Result<U> }
- 17. func ls()-> Result<[String]> func grep(pattern: String)(values: [String]) -> [String] func sort(values: [String]) -> [String] { return [] } let sorted = ls().map(grep("*.jpg")).map(sort) ls | grep *.jpg | sort
- 18. Interstellar
- 19. ls | grep *.jpg | sort
- 20. class Signal<T> { func subscribe(f: Result<T> -> Void) -> Signal<T> func next(g: T -> Void) -> Signal<T> func error(g: ErrorType -> Void) -> Signal<T> func update(result: Result<T>) func update(value: T) func update(error: ErrorType) } let signal = Signal<String>() signal.next { string in print(string) } signal.update("Hello World")
- 21. pushing instead of pulling
- 23. let threadSignal = Signal<String>() func uppercase(string: String) -> String { return string.uppercaseString } threadSignal .ensure(Thread.background) .map(uppercase) .ensure(Thread.main) .next { print($0) }
- 24. Extending UIKit to support Signals.
- 25. extension UITextField { public var textSignal: Signal<String> } let textField = UITextField() textField.textSignal.next { string in print(string) }
- 26. If it’s variable, it qualifies as a Signal.
- 27. real world code examples
- 28. func executeRequest(request: Request) -> Signal<HTTPResponse> func getURL(response: HTTPResponse) throws -> NSURL func upload(data: NSData)(url: NSURL, completion: Result<String>->Void) func createEntity(path: String, completion: Result<Conversation>->Void) func createConversation(avatar: UIImage) -> Signal<Conversation> { let signal = Signal<Conversation>() let data = UIImageJPEGRepresentation(avatar, 0.8)! api .executeRequest(.GetUploadURL) .flatMap(getURL) .flatMap(api.upload(data)) .flatMap(createEntity) .subscribe(signal.update) return signal }
- 29. func poll() -> Signal<[Conversation]> { let signal = Signal<[Conversation]>() let json = api .executeRequest(.GetConversations) .map { $0.json } let conversations = json .flatMap(Sync<Conversation>(context: context).updateObjects) let messages = json .flatMap(getMessages) .flatMap(Sync<Message>(context: context).updateObjects) conversations.merge(messages) .flatMap(context.saveAndPipe) .next { signal.update($0.0) } .error { signal.update($0) } signal.map(countUnread).next(setUnreadCount) return signal }
- 30. func poll() -> Signal<[Conversation]> { let signal = Signal<[Conversation]>() let json = api .executeRequest(.GetConversations) .map { $0.json } let conversations = json .flatMap(Sync<Conversation>(context: context).updateObjects) let messages = json .flatMap(getMessages) .flatMap(Sync<Message>(context: context).updateObjects) conversations.merge(messages) .flatMap(context.saveAndPipe) .next { signal.update($0.0) } .error { signal.update($0) } signal.map(countUnread).next(setUnreadCount) return signal } API Request sync conversations sync messages wait for both then save update unread count notify listeners
- 31. Warpdrive
- 32. • Thread.main / Thread.background • Signal.delay(seconds: NSTimeInterval) • Signal.wait throws • Signal.debounce(seconds: NSTimeInterval) Coming soon: Holodeck UIKit Bindings