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Getting Clean, Keeping Lean
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Joe Birch
March 17, 2017
Programming
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Getting Clean, Keeping Lean
Joe Birch
March 17, 2017
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Transcript
Getting clean. Keeping lean.
@hitherejoe hitherejoe joebirch.co Joe Birch - Android Engineer @ Buffer
@buffer buffer.com
Greenfield projects
None
- High-level of technical debt - Extremely tightly coupled concepts
- No unit or UI tests - Difficult to know what is going on and where No longer lean
- YOU know what is what - YOU know where
class X is - YOU know where logic for Y is - But what about along the line… No longer lean (for now) (for now) (for now)
25 50 75 100 Output Debt
25 50 75 100 Output Debt
For the sake of yours and future developers sanity -
have empathy. Be mindful of the consequences and think before you craft.
Buffer for Android
None
None
None
- Lack of architecture - Bloated activities with multiple responsibilities
- Difficult to test - Difficult to extend and maintain - Duplication of concepts == no reuse
Moving to MVP - Fear of changing too much -
Helped separate presentation logic - DataManagers to house data operations - Increased test coverage
None
None
Not enough. - Bloated DataManager classes - Future changes, offline
- where? - Presentation linked to specific data source - No clear line between responsibilites - Buffer is a big app. Data types, features, sources
Architecture “The art of planning, designing and constructing buildings”
Architecture “The art of planning, designing and constructing buildings concepts”
None
None
None
None
None
Think outside of your team.
Clean Architecture
None
Separation of Concerns
- Layers are independent of frameworks - Code becomes more
testable - Inner layers independant of UI - Inner layers independant of external parties Separation of Concerns - Bugs more isolated
None
Layer Models - Each layer has own Model classes -
Removes dependancy on external models - Easily map with Mapper classes
ModelA Mapper Model Mapper Model
Enterprise Business Rules - Application Business Objects (Entities) - Unaffected
by operational change - Can create before touching any UI
public class TournamentModel { public String id; public String
name; @SerializedName("full_name") public String status; @SerializedName("date_start") public String dateStart; @SerializedName("date_end") public String dateEnd; public int size; }
Application Business Rules - Application specific business rules - Uses
Cases - Affected by operational change - Isolated from external concerns
public class GetSchedules extends UseCase<ProfileSchedules> { private final SchedulesRepository
schedulesRepository; @Inject public GetSchedules(SchedulesRepository schedulesRepository) { this.schedulesRepository = schedulesRepository; } @Override public Single<ProfileSchedules> buildUseCaseObservable() { return schedulesRepository.getSchedules(); } }
None
Use Case Interface Interface Impl Activity Application Business Rules Interface
Adapters
Interface Adapters - Contains MVP architecture of our app -
Presenters contain ‘callbacks’ - Views define contract for implementation - Mapper converts data from external form
public class UpdatesPresenter extends BasePresenter<UpdatesMvpView> implements SingleObserver<List<Update>> { @Override public
void onSubscribe(Disposable d) { … } @Override public void onSuccess(List<Match> matches) { … } @Override public void onError(Throwable e) { … } }
Presenter Interface Interface Impl Activity Interface Adapters Frameworks & Drivers
Frameworks & Drivers - UI components (Activities, Fragments) - Networking
actions (Retrofit) - Storage (Cache & DB) - Repository Pattern for interacting with these
Repository Interface Repository Impl DataStore Interface DataStore Impl DataStore Impl
DataStore Factory
None
Layer Boundaries - Communication via abstractions (interfaces) - No direct
name references in inner layers - Instead, inner layer provides this interface - aka, The Dependancy Inversion Principle
Not limited to these layers Layer 1 Layer 2 Layer
3 Layer 4
Not limited to these layers Layer 1 Layer 2 Layer
3
Not limited to these layers Layer 1 Layer 2 Layer
3 Layer 4 Layer 5 Layer 6
Test Coverage
None
Learnings
Advantages. - High percentage of code coverage - Incredibly easy
to navigate package structure - Easier to maintain - Allows us to move faster - Focused classes and test classes
- Seperation of concerns - Define, Test, Stabilise before UI
- Futureproof implementations - Clear discipline, good practice - and more…
Disadvantages - Adds initial overhead - Takes time to get
used to - Can feel overkill for some tasks - Difficult to make decisions - Conversion of models between layers
Winston Enterprise Business Rules Application Business Rules Interface Adapters Mobile
UI TV UI Wear UI Frameworks & Drivers
Winston Enterprise Business Rules Application Business Rules Interface Adapters Mobile
UI TV UI Wear UI Frameworks & Drivers @hitherejoe hitherejoe joebirch.co
Resources https://overflow.buffer.com/2016/12/22/rebuild- android-composer/ https://github.com/googlesamples/android- architecture Clean Architecture: A Craftsman's Guide
to Software Structure and Design (Robert C. Martin)