Clean Architecture
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The document outlines the principles of clean architecture in software development, as described by Robert C. Martin, emphasizing the importance of use cases, structure, dependencies, and models. It discusses the organization of architecture into layers and the significance of separating business logic from peripheral concerns. Additionally, it addresses the implementation of clean architecture using various models and demonstrates the use of RxJava for reactive programming within this context.
Clean Architecture
- 1. Keeping it Clean: Clean code, for dirty developers - Rich King - Senior Android Developer
- 2. 100+ million installs 190 countries 100K+ lines of code 185 Activities 23 Services
- 4. Architecture
- 6. Some time passes Services ActivitiesLoadersNetwork Global Cache
- 7. And then….. Services ActivitiesEvent BusNetwork Global Cache GCM Global Listener DB
- 10. So, what is Clean Architecture?
- 11. “ A GOOD ARCHITECTURE EMPHASIZES THE USE-CASES AND DECOUPLES THEM FROM PERIPHERAL CONCERNS — Robert C. Martin
- 12. Clean Architecture • Coined by Robert C. Martin • Combination of various ideas - Hexagonal Architecture (a.k.a. Ports and Adapters) - Onion Architecture - Screaming Architecture - Data, context and interaction paradigm - Boundary, controller entity objects - Single responsibility principle https://8thlight.com/blog/uncle-bob/2012/08/13/the-clean-architecture.html
- 13. Clean Architecture Key points: 1. Use cases 2.Structure 3.Dependancies 4.Models 5.Testable
- 14. Use cases • Use cases capture business rules Send Message Bob Alice
- 15. What does it do? • Structure should indicate what the application is, not how it does it.
- 16. What does it do? • Structure should indicate what the application is, not how it does it. com.myapp activities services presenters content providers views
- 17. What does it do? • Structure should indicate what the application is, not how it does it. chat conversations com.myapp
- 20. Inversion of Control Class A Class B Dependency
- 21. Inversion of Control Class A Class B Injected
- 26. Why different models? Use Case Model •message •id •from Data Model •message •id •from •cacheTime View Model •message •id •from •itemSpacing
- 34. Clean Architecture List of Messages Open Conversation Presenter View Gateway Impl Memory Cache Disk Cache Network Gateway <I> Use Case Entity Entity Entity Bob
- 36. interface MessageGateway { List<Message> get(String conversationId); int send(String conversationId, String to, String from, String message); boolean delete(String messageId); void subscribe(Callback callback); } Gateway
- 37. class GetMessages { ... List<M> execute(conversationId) { return mMessageGateway.get(conversationId); } } Use cases
- 38. class SendMessage { ... int execute(conversationId, ...) { int result = mMessageGateway.send(...); if(result == SUCCESS) mConversationGateway.update(conversationId); return result; } } Use cases
- 39. class SendMessage { ... int execute(conversationId, ...) { int result = mMessageGateway.send(...); if(result == SUCCESS) mConversationGateway.update(conversationId); return result; } } Use cases
- 40. class SendMessage { ... int execute(conversationId, ...) { int result = mMessageGateway.send(...); if(result == SUCCESS) mConversationGateway.update(conversationId); return result; } } Use cases
- 41. class MessageScreenPresenter { ... void onSendMessage(message) { int result = mSendMessage.execute(...); switch (result) { case ERROR: mView.displayError(...) ... } } Presentation
- 42. MainThread
- 43. RxJava • Simple to switch threads • Transformations are convenient • Comes with a cost https://github.com/ReactiveX/RxJava
- 44. mExecutor.post(new Runnable() { void run() { // do something mHandler.post(new Runnable() { void run() { // publish result } }); } }); !RxJava
- 45. mExecutor.post(() -> { // do something mHandler.post(() -> { // publish result } } } } !RxJava with lambdas
- 46. doSomething() .observeOn(AndroidSchedulers.mainThread()) .subscribe(result -> /* Handle Result */) RxJava
- 47. Rx, Very Nice
- 48. interface MessageGateway { Single<List<M>> get(...); Single<Integer> send(...); Single<Boolean> delete(...); Observable<Update> subscribe(...); } Gateway
- 49. class GetMessages { ... Single<List<M>> execute(conversationId) { return mMessageRepo.get(conversationId); } } Use cases
- 50. class SendMessage { ... Single<Integer> execute(conversationId, ...) { return mMessageGateway.send(…) .doOnNext(r -> if(r == SUCCESS) mConversationGateway.update(conversationId);) } } Use cases
- 51. class MessageScreenPresenter { ... void onStart() { mSendMessage.execute(mConversationId) .observeOn(AndroidSchedulers.mainThread()) .filter(result -> result == ERROR) .subscribe(mView::displayError); ... } } Presentation
- 52. class SomeGatewayImpl { Single<Result> load(…) { return loadFromMemory() .flatMap(r -> r != null ? Single.just(r) : loadFromDB()); } } Caching simplified
- 53. class SomeGatewayImpl { Single<Result> load(…) { return loadFromMemory() .flatMap(r -> r != null ? Single.just(r) : loadFromDB()); } } Caching simplified
- 54. class SomeGatewayImpl { Single<Result> load(…) { return loadFromMemory() .flatMap(r -> r != null ? Single.just(r) : loadFromDB()); } } Caching simplified
- 55. class SomeGatewayImpl { Single<Result> load(…) { return loadFromMemory() .flatMap(r -> r != null ? Single.just(r) : loadFromDB()); } } Caching simplified
- 56. class SomeGatewayImpl { Single<Result> load(…) { return loadFromMemory() .flatMap(r -> r != null ? Single.just(r) : loadFromDB()); } } Caching simplified
- 58. Was it worth it? • Boilerplate • Learning curve • Testing • Everything has a place • Decisions can be postponed • Implementations are replaceable
- 59. How can you do it? • Start small • Discuss and experiment • Tech Talks • Code reviews