Functional Reactive Programming in an imperative world

Transcript

1. Functional Reactive Programming in an imperative world
2. @NachoSoto
3. Today: • Introduction • Imperative example • Rewriting it with RAC 3
4. Functional Programming
5. State Data over time
6. Implicit state let x = f() print(x) ===> 1 let y = f() print(y) ===> 2
11. Simple VS Easy
12. Complexity
13. #computers
14. Functional Reactive Programming
15. Demo 1 What can possibly go wrong?
16. So what's wrong with that?
17. So what's wrong with this? private var lastScheduledWord: dispatch_cancelable_block_t? private var lastRequest: NSURLSessionTask? private var numberOfRetries = 0 func newSearchString(word: String) { cancel_block(lastScheduledWord) lastRequest?.cancel() lastRequest = nil lastScheduledWord = dispatch_after_delay(THROTTLE_SECONDS) { self.lastRequest = fetchWord(word, success: { result in self.displayResult(word, result) }, failure: { error in if self.numberOfRetries++ < NUMBER_OF_RETRIES { self.newSearchString(word) } else { self.numberOfRetries = 0 self.displayError(error) } }) } }
18. So what's wrong with this? • Does it work? • Are there bugs? • Are there race conditions? What thread is each thing running on? • How can we add a new feature without adding (or multiplying) the complexity?
19. Idea
20. There is a better way Demo 2
21. let keyStrokes = searchField.keyStrokes() keyStrokes .throttle(THROTTLE_SECONDS) .flatMap { word in fetchWord(word) .retry(NUMBER_OF_RETRIES) .takeUntil(keyStrokes) .map { result in (word, result) } } .start( next: displayResult, error: displayError )
22. So what's right with this? • Does it work? • Are there bugs? • Are there race conditions? What thread is each thing running on? • How can we add a new feature without adding (or multiplying) the complexity?
23. Conclusion
24. Credits • Simple Made Easy by Rich Hickey. • Enemy of the state by Justin Spahr-Summers. • RxJS talk by Netflix.
25. Thank you