Composability with Swift

Composing things has radically changed from Objective-C, these slides are showing how we can compose things in safer way.

1. Composability with Swift let speaker = Speaker(name: "Junior B.", twitter:"@bontoJR")
2. What is Composability?
3. – Brian Beckman “Compositionality is THE way to control complexity.”
4. Composability is a way to build software creating small code blocks and later combining them.
5. – Terry Pratchett “It is important that we know where we come from, because if you do not know where you come from, you don't know where you're going.”
6. How do we compose things in Objective-C?
7. ;
8. Objective-C • We compose statements • We tell the machine what to do step by step (Imperative) • We manage states • We perform side effects all the time
9. Objective-C Composability MyVar *foo = [MyVar new]; MyVar *bar = [MyVar new]; [foo doThis]; [bar doThat]; [blabla doBlaBla]; //...
10. Async Objective-C dispatch_async(queue, ^{ // do something if (!error) { dispatch_async(queue, ^{ if (!error) { dispatch_async(dispatch_get_main_queue(), ^{ // UPDATE UI }); } //... }); } else { // display error } });
11. Is it the same in Swift?
12. There's no semicolon in Swift...
13. What can I compose in Swift? How I compose things in Swift?
14. FUNCTIONS!
15. Good Idea!
16. What is a Function? • In Swift functions are First Class Citizens • A function is an ordinary element • First class function means that they are like Int, Double, Array, etc…
17. In Swift a FUNCTION is just DATA.
19. What can I do composing data? • Create complex algorithms combining small reusable functions • Asynchronous programming • Error handling • …there’s not enough space to list all the things!
20. In a Nutshell • Composing data means that I can compose types (structs or classes) with functions • The composition of different entities is achieve taking advantage of Generics • Composing things will make the compiler the first checker for errors
21. Example 1: Result • A type Result can hold either a value or an error • Results can be composed to create a chain • Errors are propagated to the chain • The type checker will prevent type mismatch!
22. Result - Error Handling
23. Result - Chaining
24. AWESOME! But what about asynchronous tasks?
25. Example 2: Future • A type Future is a placeholder for a value that is still not available, but that will be (Latency) • Futures can be composed to create an asynchronous chain • Errors are propagated to the chain • The origin of the term is a proposal for the call-by- future evaluation method
26. Future - Error Handling
27. Not Sure… …but seems familiar.
28. Same concept of Result! AWESOME x2!
29. Future - Chaining
30. DEMO
31. Future / Promise • A Future is a read-only placeholder • A Promise is a write-able placeholder • A Promise is a subclass of Future
32. CALLBACKS ARE IMPERATIVE…
33. PROMISES ARE FUNCTIONAL!
34. Conclusions • Composing data is a very good WAY to control complexity • Big features can be create composing small chunks of code (bricks) • Code is more readable and more maintainable
35. Where to go from here • Composition with Future and Promise is very powerful, but has limits (ex: resource management) • Future and Promise are single value, what about multiple values? (sequences)
36. The Reactive Way • Reactive Programming is the NATURAL evolution of data composition • Asynchronous Programming is easier and more fun using the Reactive style!
37. Good Resources After This RxSwift SideEffects.xyz (yeah, that’s a domain…) Brian Beckman: Don't fear the Monad Erik Meijer: What does it mean to be Reactive? Ash Furrow: Functional Reactive Awesomeness With Swift!
39. Thank You! @bontoJR
40. Q A uestions nswers