Building a testable mixed-codebase ios Framework

Transcription

1 Building a testable mixed-codebase ios Framework Nikos Maounis ios Christos Karaiskos ios

2 Outline Introduction and Motivation Distributing Libraries and Resources Design Considerations Testability Swift and ObjC Coexistence

3 Introduction The App Store evolution

4 Introduction The App Store evolution

5 Introduction New Horizons Extend beyond the traditional app experience Quick interactions with your app throughout the OS and throughout different devices

6 Introduction Shared Code Location Location Logging Networking Logging Networking Analytics Resources Analytics Resources Reachability Reachability

7 Motivation Be at the edge of innovation, follow changes in the app and device landscape (widget, watch, notifications, Siri, Maps) Lay the foundations for the future, with focus on code reuse, testability and self-documentation for new team members Prepare for complete and safe transition to Swift, with unit-test assurance

8 Distributing Libraries and Resources

9 Static Libraries Names of the form libname.a Archives of object files Statically linked objects become part of executable: Increase in size Separate distribution of headers and resources Changes require re-linking Swift does not support them

10 Dynamic Libraries Names of the form dynamiclibrary.dylib Single copy of objects is shared among different applications Symbol binding performed at runtime. Not being able to find and load a required dylib will crash your app. Not part of main executable: Static linker only makes note of the install names of dylibs that are referenced by symbols in your app Versioned: dylibs may be updated independently of their consumers (i.e., minor version updates)

11 Frameworks Names of the form frameworkname.framework Act as dylib wrappers, inherit all their characteristics Bundle format, relocatable Include dynamic library, headers, resources, versioning info Resources include: NIB files, images, localised strings, etc.

12 User Frameworks in ios Introduced in ios 8, support Swift The official way to package reusable code with resources, without requiring hacks (e.g. static frameworks) Due to sandbox restrictions, each application must embed its own copy (along with any further dylib/framework dependencies) Frameworks cannot be updated alone, even bumping the minor version requires resubmitting the whole application Conversely: They are easier to handle, with the guarantee that the correct version of the framework will run, new versions won t break anything in previous versions

13 Design Considerations

14 Swift vs ObjC in Taxibeat Github Linguist 23.5% 76.5% Passenger 26.2% 73.8% Driver

15 Our Approach Use both ObjC and Swift. Migrate to pure Swift when framework is stable and tested. New classes should be written in Swift. Focus on model part of MVC. Determine parts heavily shared among apps and extensions (e.g. location management, networking, logging) Treat Framework as a clean room: warnings as errors, unit tests, code reviews, design patterns, double-think before adding functionality Code organization. Different project, different repo, same workspace Don t risk client stability. If migration of a class from client to framework is not straightforward, keep both so that nothing breaks and replace only when tests pass.

16 Project Organization

17 Extensions ld: warning: linking against a dylib which is not safe for use in application extensions Check Allow app extension API only Compiler-enforced restriction on what you can include in framework Ensures that what you build can be used in extensions.

18 Architectural Differences A framework target can only be built for a single platform, and the respective supported architectures Solution for deploying to watchos or tvos: Separate framework target for each platform Use Swift directives (e.g., #if os(watchos)), different platforms support different system API subsets

19 Testability in Mind

20 The Importance of Tests Confidence to refactor Test assisted design promotes good API design. Find flaws early and iterate. Modularity and loose coupling by definition Simulate edge scenarios using fake objects Dynamic documentation

21 Xcode Server Coverage Stats We created an Xcode Server to force ourselves to write tests

22 Example 1: Unit Testing the Location Manager

23 Example 1: Unit Testing the Location Manager Need to simulate location and authorization scenarios Override the need for depending on actual hardware measurements (GPS, A/GPS) Override the need for user input (Permissions etc)

24 Example 1: Unit Testing the Location Manager Continuous user tracking not always required throughout app lifecycle, battery drain ios >= 9 provides requestlocation() using delegation Closure/block-based approach: ease of use, compact, code not scattered public class LocationManager: NSObject { } public func ((CLLocation) -> Void)) { // LocationManager saves closure, internally handles inaccurate locations, lack of authorization etc. // when sufficiently accurate location is retrieved, closure is called } Execute callback when sufficiently accurate location is acquired

25 Example 1: Unit Testing the Location Manager In order to unit test our LocationManager we need to control the CLLocationManager which is used internally Step 1: Subclass CLLocationManager (or define a protocol with common functions) extension LocationManagerTests { public class MockRequestOnceSuccessLocationManager: CLLocationManager { override class func locationservicesenabled() -> Bool { return true } override class func authorizationstatus() -> CLAuthorizationStatus { return.authorizedwheninuse } } } override public func startupdatinglocation() { delegate?.locationmanager?(self, didupdatelocations: [CLLocation(latitude: 10.0, longitude: 10.0)]) }

26 Example 1: Unit Testing the Location Manager Step 2: Inject dependency to our LocationManager Init for LocationManager init(locationmanagertype:cllocationmanager.type = CLLocationManager.self) { } Create new instance: locmgr = LocationManager(locationManagerType: MockRequestOnceSuccessLocationManager.self) // TEST Step 3: Remove hardcoded references of CLLocationManager within LocationManager self.locationmanagertype.authorizationstatus() instead of CLLocationManager.authorizationStatus()

27 Example 1: Unit Testing the Location Manager Step 4: Write an asynchronous test Test case for successful scenario class LocationManagerTests: XCTestCase { var locmgr: LocationManager! var exp: XCTestExpectation! func testrequestonceallowedwheninuse() { exp = self.expectation(description: "Request once callback") locmgr = LocationManager(locationManagerType: MockRequestOnceSuccessLocationManager.self) locmgr.requestlocationonce(completion: { (location) in XCTAssertEqual(location.coordinate.latitude, 10.0) XCTAssertEqual(location.coordinate.longitude, 10.0) self.exp.fulfill() }) self.waitforexpectations(timeout: 2.0, handler: nil) } }

28 Example 2: From Localytics to Google Analytics Tight coupling with 3rd party libraries - (IBAction)favoriteButtonPressed:(id)sender { [Localytics tagevent:@"favoritebuttonpressed" attributes:@{ }]; // handle action } - (IBAction)favoriteButtonPressed:(id)sender { id<gaitracker> tracker = [[GAI sharedinstance] defaulttracker]; [tracker send:[[gaidictionarybuilder createeventwithcategory:@"somecategory" action:@"favoritebuttonpressed" label:@"somelabel" value:nil] build]]; } Be careful not to become too coupled with 3rd-party applications Unit testing revealed that as consumers we just want to log events Consumers don t care if it s Google Analytics or Localytics under the hood

29 Example 2: From Localytics to Google Analytics + (void)sendhittoproviderwithname:(nsstring *)eventname andparameters:(nsdictionary *)params { [Localytics tagevent:eventname attributes:params]; } + (void)sendhittoproviderwithname:(nsstring *)eventname andparameters:(nsdictionary *)params { id<gaitracker> tracker = [[GAI sharedinstance] defaulttracker]; [tracker send:[[gaidictionarybuilder createeventwithcategory:@"ui_action" action:eventname label:@"app action" value:nil] build]]; } - (IBAction)favoriteButtonPressed:(id)sender { [BKAnalyticsHelper sendhittoproviderwithname:@"favoritebuttonpressed" andparameters:@{}]; // handle action } Create an abstraction layer, hide actual implementation details Migration transparent to consumer (besides the API key initializer) Changes required within single class, not scattered throughout project

30 Swift and ObjC Coexistence

31 Exposing ObjC Symbols Umbrella header, named MyFramework.h Exposes Objective-C/C classes as public Similar to Bridging header of mixedcodebase app target Should include all the ObjC headers you want disclosed in your public API Be sure to mark the header file as Public in the inspector

32 Exposing Swift Symbols Use access control to restrict visibility to parts of your code from code in other source files and modules Explicitly mark classes and methods as public if you want them exposed (default is internal)

33 Namespaces Swift supports namespaces ObjC does not. Convention is 3-character prefixing Solution for exposing Swift public class Logger: NSObject { } public func logdebug(_ params:any...) { //... } Seen in ObjC as: TXBLogger : NSObject + (void)logdebug; - (nonnull instancetype)init

34 Pure Swift Features As long as there is ObjC we cannot fully take advantage of Swift s powerful features We could not use optional primitives, associated value enums, structs, tuples, nested classes, default function params etc. Solution: Use pure Swift features only for internal Swift classes that do not interact with ObjC. If at some point they need to, write wrapper methods (e.g. to expose a String enum to ObjC)

35 Delegation in Swift (1/2) Handling weak references in delegates strong reference to A Solution(??): declare delegate var weak, as in ObjC

36 Delegation in Swift (2/2) Solution: Declare the protocol to inherit from class and property weak delegate released when it goes out of method scope

37 Being Swifty Use guard to exit functions early Use type inference Use the trailing closure syntax Follow case conventions. Names of types and protocols are UpperCamelCase. Everything else is lowercamelcase. Default to structs unless you really need a class Favor immutable variables

38 Being Swifty Example 1 Map reduce filter vs C-style loop NSArray<NSNumber *> @5]; NSMutableArray *finalarray = [[NSMutableArray alloc] init]; for (NSInteger i = 0; i <= samplearray.count; i++) { NSNumber *idoubled = [NSNumber numberwithinteger: samplearray[i].integervalue * 2]; [finalarray addobject:idoubled]; } let samplearray = [1, 2, 3, 4, 5] let finalarray = samplearray.map { return $0*2 }

39 Being Swifty Example 2 Naming conventions typedef NS_ENUM(NSInteger,TXBStatusViewState) { kstatusviewstatenone, kstatusviewstatewaiting, kstatusviewstatenoavailabledrivers, kstatusviewstateunsupportedarea, kstatusviewstatemain, kstatusviewstateaddress, kstatusviewstateblocked, kstatusviewstatenointernet }; let statusviewmode: TXBStatusViewState =.statusviewstateblocked //NOT SWIFTY typedef NS_ENUM(NSInteger,TXBStatusViewState) { TXBStatusViewStateNone, TXBStatusViewStateWaiting, TXBStatusViewStateNoAvailableDrivers, TXBStatusViewStateUnsupportedArea, TXBStatusViewStateMain, TXBStatusViewStateAddress, TXBStatusViewStateBlocked, TXBStatusViewStateNoInternet }; let statusviewmode: TXBStatusViewState =.blocked //SWIFTY

40 Being Swifty Example 3 Type Safety [[NSNotificationCenter defaultcenter] addobserver:self selector:@selector(_badrequestnotification:) name:@"krequestbadnotification" object:nil]; NotificationCenter.default.addObserver(self, selector: #selector(self.badrequestnotification), name: Notification.Name.requestBad, object: nil)

41 Coming Soon Taxibeat Widget

42 ios.conf app The.Conf app is built using embedded frameworks for the Watch App and we made it open source on Github

43 ios.conf app we made it open source on Github Questions? enum SupportedLanguages { case # case $ }

44 Questions

45 CocoaPods Single Podfile for both projects, same workspace pod update acts on both projects source ' Specs.git' workspace 'MyWorkspace' platform :ios, '9.0' use_frameworks! target 'MyProject' do project 'MyProject.xcodeproj' pod 'FBSDKCoreKit' pod 'FBSDKLoginKit' pod 'FBSDKShareKit' pod 'FBSDKMessengerShareKit' pod 'Fabric' pod 'Crashlytics' end target 'MyFramework' do project../ios-framework/ MyFramework/MyFramework.xcodeproj' pod 'CocoaLumberjack' end

46 Warnings as errors Static Analyzer (ObjC): Localized Strings missing comments Treat warning as errors

47 API Design Example 1: Request Location Once [[TXBLocationManager sharedinstance] requestlocationoncewithcompletion:^(cllocation * _Nonnull location) { }]; // center map to user location

48 Mock URLSession class MockSession: URLSession { var completionhandler:((data?, URLResponse?, Error?) -> Void)? static var mockresponse: (data: Data?, urlresponse: URLResponse?, error: NSError?) override class var shared: URLSession { return MockSession() } override func datatask(with request: URLRequest, (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask { self.completionhandler = completionhandler return MockTask(response: MockSession.mockResponse, completionhandler: completionhandler) } class MockTask: URLSessionDataTask { typealias Response = (data: Data?, urlresponse: URLResponse?, error: NSError?) var mockresponse: Response let completionhandler: ((Data?, URLResponse?, Error?) -> Void)? init(response: Response, completionhandler:((data?, URLResponse?, Error?) -> Void)?) { self.mockresponse = response self.completionhandler = completionhandler } } } override func resume() { completionhandler!(mockresponse.data, mockresponse.urlresponse, mockresponse.error) }

49 Organization Separate project and git repo Same workspace (already setup due to CocoaPods) Alternatives: Subproject, different target [1] [1]