Generics With Swift

for iOS meetup in Singapore
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Transcript

1. Generics with Swift by akira hirakawa @akirahrkw
2. Do you Swift?
3. we use swift for Burpple app
5. Generics with Swift
6. Do you use Generics?
7. example
8. swap two Int values func swapTwoInts(inout a: Int, inout b: Int) { let temporaryA = a a = b b = temporaryA }
9. swap two Double values func swapTwoDoubles(inout a: Double, inout b: Double) { let temporaryA = a a = b b = temporaryA }
10. swap two String values func swapTwoStrings(inout a: String, inout b: String) { let temporaryA = a a = b b = temporaryA }
11. these are identical !!
12. more useful more flexible?
13. generics !!
14. Generic function func swapTwoValues<T>(inout a: T, inout b: T) { let temporaryA = a a = b b = temporaryA }
15. swap Int values var someInt = 3 var anotherInt = 107 swapTwoValues(&someInt, &anotherInt)
16. swap String values var someString = "hello" var anotherString = "world" swapTwoValues(&someString, &anotherString)
17. can not var someInt = 3 var anotherString = "world" swapTwoValues(&someInt, &anotherString)
18. useful flexible
19. but
20. why not use Protocol?
21. can
22. swap two Any values func swapTwoValues(inout a: Any, inout b: Any) { let temporaryA = a a = b b = temporaryA }
23. var a = 1 as Any var b = 2 as Any swapTwoValues(&a, &b)
24. var a = “a” as Any var b = “b” as Any swapTwoValues(&a, &b)
25. but
26. var a = 1 as Any var b = “a” as Any swapTwoValues(&a, &b)
27. which is better?
28. what is the difference?
29. func executeProtocol(p: Printable) -> Printable { } func executeGenerics<T: Printable>(p: T) -> T { }
30. almost same
31. func executProtocol(p: Printable) -> Printable { p.description return p } func executeGenerics<T: Printable>(p: T) -> T { p.description return p }
32. no difference?
33. return value
34. func executProtocol(p: Printable) -> Printable { return p } func executeGenerics<T: Printable>(p: T) -> T { return p }
35. -> Printable you need to cast to use the return value var movie: Movie = … var p: Printable = executProtocol(movie) (p as Movie).show()
36. -> T you don’t need to cast to use the value var movie: Movie = … movie = executeGenerics(movie) movie.show()
37. useful
38. different
39. performance?
40. case swap method:
41. case increment:
42. depends on -O and swift version
43. fast useful flexible
44. in practice?
45. case DataSource:
46. but
47. case DataSource:
48. Generics doesn’t work on TableViewDeleate, TableViewDataSource because of a bug ds.respondsToSelector(“tableView:numberOfRo wsInSection:”) is false http://www.openradar.me/radar? id=5829206453780480
49. case API Call:
50. Request<T>
51. Request<[User]>
52. Object Mapper
53. AnyObject -> T var orm = { (json: AnyObject) -> User in … … return user } var orm = { (json: AnyObject) -> Media in … … return media }
54. Completion Handler
55. T -> () var handler = { ( item:User) -> () in … … } var handler = { (item:Media) -> () in … … }
56. fast useful flexible practical
57. I like generics :)
58. thanks
59. bit.ly/tinyjson bit.ly/code20150416
60. question?