Protocol-Oriented Programming in Networking

Transcript

1. PROTOCOL-ORIENTED PROGRAMMING IN NETWORKING ISHKAWA
2. ISHKAWA?
3. OVERVIEW PROTOCOL-ORIENTED PROGRAMMING IN NETWORKING 1. Wrapping NSURLSession using protocols 2. Generic programming on the protocols 3. Combination with RxSwift
4. TOPIC 1 Wrapping NSURLSession using protocols To make call-site code simpler To get responses type-safely
5. GOAL
6. GOAL l e t r e q u e s t = R e q u e s t ( ) S e s s i o n . s e n d R e q u e s t ( r e q u e s t ) { r e s u l t i n / / r e s u l t : R e s u l t < R e q u e s t . R e s p o n s e , E r r o r > }
7. GOAL l e t r e q u e s t = C r e a t e I s s u e R e q u e s t ( r e p o s i t o r y I D : 1 2 3 , t i t l e : " T e s t " ) S e s s i o n . s e n d R e q u e s t ( r e q u e s t ) { r e s u l t i n / / r e s u l t : R e s u l t < I s s u e , E r r o r > } l e t r e q u e s t = S e a r c h R e p o s i t o r i e s R e q u e s t ( q u e r y : " s w i f t " ) S e s s i o n . s e n d R e q u e s t ( r e q u e s t ) { r e s u l t i n / / r e s u l t : R e s u l t < P a g i n a t i o n R e s p o n s e < R e p o s i t o r y > , E r r o r > } The type of result changes depending on the request type
8. WHY PROTOCOL? 1. To associate response type with request type 2. To provide flexible default implementation
9. WHY PROTOCOL? 1. To associate response type with request type 2. To provide flexible default implementation
10. ASSOCIATING RESPONSE TYPE WITH REQUEST TYPE p r o t o c o l R e q u e s t T y p e { t y p e a l i a s R e s p o n s e v a r b a s e U R L : N S U R L { g e t } v a r m e t h o d : H T T P M e t h o d { g e t } v a r p a t h : S t r i n g { g e t } v a r p a r a m e t e r s : [ S t r i n g : A n y O b j e c t ] { g e t } f u n c r e s p o n s e F r o m O b j e c t ( o b j e c t : A n y O b j e c t , U R L R e s p o n s e : N S H T T P U R L R e s p o n s e ) t h r o w s - > R e s p o n s e }
11. ASSOCIATING RESPONSE TYPE WITH REQUEST TYPE c l a s s S e s s i o n { . . . f u n c s e n d R e q u e s t < R e q u e s t : R e q u e s t T y p e > ( r e q e u s t : R e q u e s t , h a n d l e r : R e s u l t < R e q u e s t . R e s p o n s e , E r r o r > - > V o i d ) { d o { l e t d a t a : N S D a t a = . . . l e t j s o n : A n y O b j e c t = . . . l e t r e s p o n s e = r e q u e s t . r e s p o n s e F r o m O b j e c t ( j s o n . . . ) h a n d l e r ( . S u c c e s s ( r e s p o n s e ) ) / / R e q u e s t . R e s p o n s e } c a t c h { h a n d l e r ( . F a i l u r e ( e r r o r ) ) } } }
12. ASSOCIATING RESPONSE TYPE WITH REQUEST TYPE l e t r e q u e s t = C r e a t e I s s u e R e q u e s t ( r e p o s i t o r y I D : 1 2 3 , t i t l e : " T e s t " ) S e s s i o n . s e n d R e q u e s t ( r e q u e s t ) { r e s u l t i n / / r e s u l t : R e s u l t < I s s u e , E r r o r > } l e t r e q u e s t = S e a r c h R e p o s i t o r i e s R e q u e s t ( q u e r y : " s w i f t " ) S e s s i o n . s e n d R e q u e s t ( r e q u e s t ) { r e s u l t i n / / r e s u l t : R e s u l t < P a g i n a t i o n R e s p o n s e < R e p o s i t o r y > , E r r o r > } The type of result changes depending on the request type
13. WHY PROTOCOL? 2. To provide flexible default implementation 1. To associate response type with request type
14. PROVIDING DEFAULT IMPLEMENTATION PART 1: COMMON CONFIGURATIONS p r o t o c o l G i t H u b R e q u e s t T y p e : R e q u e s t T y p e { } e x t e n s i o n G i t H u b R e q u e s t T y p e { v a r b a s e U R L : N S U R L { r e t u r n N S U R L ( s t r i n g : " h t t p s : / / a p i . g i t h u b . c o m " ) ! } }
15. PROVIDING DEFAULT IMPLEMENTATION PART 2: PROTOCOL FOR JSON DECODING s t r u c t S e a r c h R e p o s i t o r i e s R e q u e s t : G i t H u b R e q u e s t T y p e { f u n c r e s p o n s e F r o m O b j e c t ( o b j e c t : A n y O b j e c t , U R L R e s p o n s e : N S H T T P U R L R e s p o n s e ) t h r o w s - > R e s p o n s e { g u a r d l e t d i c t i o n a r i e s = o b j e c t a s ? [ [ S t r i n g : A n y O b j e c t ] ] e l s e { t h r o w I n v a l i d O b j e c t ( o b j e c t ) } l e t r e p o s i t o r i e s = d i c t i o n a r i e s . m a p { t r y R e p o s i t o r y ( $ 0 ) } l e t h a s N e x t P a g e = . . . r e t u r n P a g i n a t i o n R e s p o n s e ( e l e m e n t s : r e p o s i t o r i e s , h a s N e x t P a g e : h a s N e x t P a g e ) }
16. PROVIDING DEFAULT IMPLEMENTATION PART 2: PROTOCOL FOR JSON DECODING p r o t o c o l D e c o d a b l e { s t a t i c f u n c d e c o d e ( o b j e c t : A n y O b j e c t ) t h r o w s - > S e l f }
17. PROVIDING DEFAULT IMPLEMENTATION PART 2: PROTOCOL FOR JSON DECODING e x t e n s i o n R e q u e s t T y p e w h e r e R e s p o n s e : D e c o d a b l e { f u n c r e s p o n s e F r o m O b j e c t ( o b j e c t : A n y O b j e c t , U R L R e s p o n s e : N S H T T P U R L R e s p o n s e ) t h r o w s - > R e s p o n s e { r e t u r n R e s p o n s e . d e c o d e ( o b j e c t ) } }
18. PROVIDING DEFAULT IMPLEMENTATION PART 2: PROTOCOL FOR JSON DECODING s t r u c t S e a r c h R e p o s i t o r i e s R e q u e s t : G i t H u b R e q u e s t T y p e { l e t q u e r y : S t r i n g / / M A R K : R e q u e s t T y p e t y p e a l i a s R e s p o n s e = P a g i n a t i o n R e s p o n s e < R e p o s i t o r y > v a r m e t h o d : H T T P M e t h o d { r e t u r n . G E T } v a r p a t h : S t r i n g { r e t u r n " / s e a r c h / r e p o s i t o r i e s " } v a r p a r a m e t e r s : A n y O b j e c t { r e t u r n [ " q " : q u e r y ] } }
19. WHY PROTOCOL? 1. To associate response type with request type Simpler and safer call-site 2. To provide flexible default implementation Documentation-like request definition
20. LINKS APIKit: RequestType, Session, etc. Himotoki: Decodable, etc. https://github.com/ishkawa/APIKit https://github.com/ikesyo/Himotoki
21. TOPIC 2 Practical example of generic programming on protocols Example: Pagination
22. PAGINATION REQUEST c u r l - v h t t p s : / / a p i . g i t h u b . c o m / s e a r c h / r e p o s i t o r i e s ? q = s w i f t & p a g e = 1
23. PAGINATION REQUEST p r o t o c o l P a g i n a t i o n R e q u e s t T y p e : R e q u e s t T y p e { t y p e a l i a s R e s p o n s e : P a g i n a t i o n R e s p o n s e T y p e v a r p a g e : I n t { g e t } f u n c r e q u e s t W i t h P a g e ( p a g e : I n t ) - > S e l f }
24. PAGINATION RESPONSE H T T P / 1 . 1 2 0 0 O K S e r v e r : G i t H u b . c o m C o n t e n t - T y p e : a p p l i c a t i o n / j s o n ; c h a r s e t = u t f - 8 L i n k : < h t t p s : / / a p i . g i t h u b . c o m / . . . > ; r e l = " n e x t " { " t o t a l _ c o u n t " : 3 8 2 6 2 , " i n c o m p l e t e _ r e s u l t s " : f a l s e , " i t e m s " : [ . . . ] }
25. PAGINATION RESPONSE p r o t o c o l P a g i n a t i o n R e s p o n s e T y p e { t y p e a l i a s E l e m e n t : D e c o d a b l e v a r e l e m e n t s : [ E l e m e n t ] { g e t } v a r h a s N e x t P a g e : B o o l { g e t } }
26. PAGINATION CLIENT c l a s s P a g i n a t i o n C l i e n t < R e q u e s t : P a g i n a t i o n R e q u e s t T y p e > { l e t b a s e R e q u e s t : R e q u e s t l e t u p d a t e H a n d l e r : V o i d - > V o i d i n i t ( b a s e R e q u e s t : R e q u e s t , u p d a t e H a n d l e r : V o i d - > V o i d ) { . . . } v a r e l e m e n t s : [ R e q u e s t . R e s p o n s e . E l e m e n t ] v a r h a s N e x t P a g e : B o o l v a r p a g e : I n t f u n c r e f r e s h ( ) { . . . } f u n c l o a d N e x t P a g e ( ) { . . . } }
27. PAGINATION CLIENT f u n c r e f r e s h ( ) { l e t r e q u e s t = b a s e R e q u e s t . r e q u e s t W i t h P a g e ( 1 ) S e s s i o n . s e n d R e q u e s t ( r e q u e s t ) { r e s u l t i n s w i t c h r e s u l t { c a s e . S u c c e s s ( l e t r e s p o n s e ) : s e l f . p a g e = p a g e s e l f . e l e m e n t s = r e s p o n s e . e l e m e n t s s e l f . h a s N e x t P a g e = r e s p o n s e . h a s N e x t P a g e s e l f . u p d a t e H a n d l e r ( ) c a s e . F a i l u r e ( l e t e r r o r ) : / / h a n d l e e r r o r } } }
28. GENERIC PROGRAMMING ON PROTOCOLS More type constraints, more detailed implementation
29. TOPIC 3 Advanced example with reactive streams
30. RXPAGINATION
31. PAGINATION VM WITH RXSWIFT c l a s s P a g i n a t i o n V i e w M o d e l < T : P a g i n a t i o n R e q u e s t T y p e > { i n i t ( b a s e R e q u e s t : T ) { . . . } / / I n p u t l e t r e f r e s h T r i g g e r : P u b l i s h S u b j e c t < V o i d > l e t n e x t P a g e T r i g g e r : P u b l i s h S u b j e c t < V o i d > / / O u t p u t l e t e l e m e n t s : O b s e r v a b l e < [ R e q u e s t . R e s p o n s e . E l e m e n t ] > l e t h a s N e x t P a g e : O b s e r v a b l e < B o o l > l e t l o a d i n g : O b s e r v a b l e < B o o l > }
32. LIVE!
33. STEPS TO IMPLEMENT PAGINATION Give a base request to ViewModel Bind input and output streams
34. CONCLUSION PROTOCOL-ORIENTED IN NETWORKING 1. Protocol is a good choice for abstraction of networking 2. More type constraints, more detailed implementation 3. Abstraction of event stream is also nice
35. TRY! POP