iOS backend wrappers for hipsters

I describe the approach, frameworks & tools which we are using at Wargaming.net to communicate with our backend APIs

Transcript

1. iOS backend wrappers for hipsters* Denis Lebedev,! iOS Dev @ Wargaming
2. Agenda • What we do! • Code & libs! • Infrastructure & tools! • Distribution
3. Service Mobile Apps department • “Assistant” apps for player engagement! • One of the largest WG API consumers! • Quality is one of the main goals! • New tools & approaches are welcome
4. 3rd party APIs
5. WGNAPIClient • Separate project! • Developed with love & unit tests in mind! • Will be open sourced some day
6. Requirements • Different cache invalidation time for entities! • Wraps every available method of API! • As stable as possible (API “unexpectedly changes”)! • Supports “partial entities”! • Out-of-the-box usage
7. WGNAPIClient 0.5 • Based on AFNetworking! • Only WOT API! • Core Data as cache system (tried even SQL)! • “Manual” entities parsing! • Extremely low code reuse! • Unit tests code is awful
8. Architecture WGNClient WGNPlayersOperation WGNDataParser WGNPlayer WGNCache The same for each entity
9. Async CoreData cache • NSManagedObjectIDs here and there! • Tries to fetch existing item with ID and updates it if it exists! • Object-graph is only partially filled
10. Old-school parsing WOWPPlane *plane = [[WOWPPlane alloc] init]; ! plane.name = json[@“name"]; ! if ([json[@"type"] isEqualToString:@"assault"]) { plane.type = WOWPPlaneTypeAssault; } else { plane.type = WOWPPlaneTypeFighter; } ! plane.priceCredit = json[@"price"];
11. Block-based APIs • Cooler than delegates!! • Good for callbacks! • Everyone likes blocks
12. [WOWPClient tanksWithCompletion:^(NSArray * tanks) { }];
13. [WOWPClient tanksWithCompletion:^(NSArray * tanks) { } error:^(NSError *error){ }];
14. [WOWPClient usersWithCompletion:^(NSArray *users){ [WOWPClient clansWithCompletion:^(NSArray * clans) { [WOWPClient tanksWithCompletion:^(NSArray * tanks) { } error:^{}]; } error:^{}]; } error:^{}];
15. BOOM
16. WGNAPIClient 1.0 • Nice, clean architecture! • Well-tested! • Includes Core/Tanks/Planes components
17. Architecture WGNClient WOWPlayer WOWPClient WOTClient WOTPlayer
18. Reactive Cocoa https://github.com/ReactiveCocoa/ReactiveCocoa
19. What? • Composes and transforms streams of values! • Functional Reactive Programming in Obj-C http://en.wikipedia.org/wiki/ Functional_reactive_programming
20. Signals • Represent data that will be delivered later! • Can be chained/merged! • Have optional next/error/completed “callbacks”
21. [RACObserve(self, newName) subscribeNext:^(NSString *newName) { NSLog(@"%@", newName); }];
22. [[RACObserve(self, language) ! filter:^(NSString *newName) { return [newName hasPrefix:@"j"]; }] ! subscribeNext:^(NSString *newName) { NSLog(@"%@", newName); }];
23. - (RACSignal *)fetchPlaneDetails:(NSArray *)IDs; - (RACSignal *)fetchPlanes; ! … WGNAIClient public API
24. Not so nested callbacks ! [[[[WOTClient sharedClient] fetchPlayers:nil] ! flattenMap:^RACStream *(NSArray *players) { return [[WOTClient sharedClient] fetchClans:nil]; ! }] flattenMap:^RACStream *(id clans) { return [[WOTClient sharedClient] fetchClans:nil]; }];
25. One point of error/result handling ! [[[[[WOTClient sharedClient] fetchPlayers:nil] ! flattenMap:^RACStream *(NSArray *players) { return [[WOTClient sharedClient] fetchClans:nil]; ! }] flattenMap:^RACStream *(id clans) { return [[WOTClient sharedClient] fetchClans:nil]; ! }] subscribeNext:^(id tanks) { //success } error:^(NSError *error) { //error }];
26. Under the hood - (RACSignal *)fetchPlanesWithFields:(NSArray *)fields { ! return [self getPath:@“encyclopedia/planes" ! parameters:@{@"fields": PARAM(fields)} ! resultClass:WOWPShortPlane.class]; }
27. https://gist.github.com/garnett/7265957 Bind RAC to AFNetworking
28. Caching 2.0 • Say “NO” to CoreData! • Cache all the things! • Uniform approach for any entity
29. Mantle! https://github.com/github/Mantle
30. Mantle benefits • Maps backend entities to model layer! • Nested models! • Attribute transformers! • NSManagedObject support! • Implements <NSCoding>
31. How to use 1. Create MTLModel subclass! 2. Implement <MTLJSONSerializing> protocol! 3. Use MTLJSONAdapter to parse
32. MTLModel *parsedObject = [MTLJSONAdapter modelOfClass:resultClass fromJSONDictionary:JSONDictionary error:&error]; + (NSDictionary *)JSONKeyPathsByPropertyKey { return [ @{ @"clanID": @"clan_id", @"name" : @"nickname"}]; }
33. “Mantle doesn't automatically persist your objects for you.”
34. NSURLCache • Works on the network protocol level! • Caches response by it’s URL! • 2 LOC to implement* NSURLCache *urlCache = [[NSURLCache alloc] initWithMemoryCapacity:kInMemoryCacheSize diskCapacity:kOnDiskCacheSize diskPath:path]; [NSURLCache setSharedURLCache:urlCache];
35. But … • Depends on backend implementation! • Response parsed again after each request
36. Tweak NSURLCache • Add necessary cache headers on client side! • Full control of caching time! • Reference implementation: https:// gist.github.com/garnett/7266332
37. Unit tests • Test models! • Test “public” signals! • One unit-test for the cache
38. Async tests of block-based APIs! =! PAIN
39. Async tests of block-based APIs! was! PAIN
40. Unit-test lifesavers • Kiwi (shouldEventually matcher)! • OHTTPStubs ! • ReactiveCocoa
41. stubResponse(@"account/list", @“players.json"); ! RACSignal *searchRequest = [client searchPlayers:@"garnett" limit:0]; ! NSArray *response = [searchRequest asynchronousFirstOrDefault:nil success:&success error:&error]; ! [error shouldBeNil]; [[response should] beKindOfClass:NSArray.class]; [[response should] haveCountOf:3];
42. OHTTPStubs shortcuts https://gist.github.com/garnett/7267579
43. Continuous integration • Teamcity! • xctool! • gcov (code coverage)
44. xctool • Same interface as in xcodebuild! • No mess with simulator! • Fancy (or even custom) build output
46. gcov • Helps to track what’s not tested! • Managers like “green lights”
47. http://habrahabr.ru/post/150438/
48. Distribution • CocoaPods + subspecs pod ‘WGNAPIClient/WOT’ pod ‘WGNAPIClient/WOWP’
49. Hipster picture
50. Thanks!