Independent Features - Powered by Dagger Extensions

Every application consists of high level features which can be built completely isolated and independent, but what are the benefits of having independent features and when does it make sense to have them?

This talk will not only answer those questions, but also show why this was not entirely possible with vanilla Dagger and how new extensions both Hilt and Anvil (previously known as Hepheastus) solve this problem. You will see these libraries in action and learn about one of their core benefits.

- Presented in DevFest Italia (17.10.2020) - https://youtu.be/U9GvDJvTejI
- Presented in MobileOptimized (07.11.2020) - https://youtu.be/069TN7oDd9M

Transcript

1. Independent Features Powered by Dagger Extensions @yahyabayramoglu
2. Live Demo
3. Why Independent Features?
4. Why Independent Features? Technical Aspect • Clear separation • Put more thoughts in development • Less entangled codebase Practical Aspect • Ownership • Easy to reuse • Isolated build
5. Feature Dependency Structure
6. Feature Dependency Structure Application Feature Input Self maintained Requires registration
7. Problem?
8. Problem? @ApplicationScope @Component( modules = arrayOf( NetworkModule::class, FirebaseModule::class, MapProviderModule::class, OnlyFeature1RelatedModule::class, ThenFeature2Module::class, GlobalApiModule::class, // ... ) ) interface ApplicationComponent
9. Problem? @ApplicationScope @Component( modules = arrayOf( NetworkModule::class, FirebaseModule::class, MapProviderModule::class, OnlyFeature1RelatedModule::class, ThenFeature2Module::class, GlobalApiModule::class, // ... ) ) interface ApplicationComponent
10. Solution? @ApplicationScope @Component( modules = arrayOf( NetworkModule::class, FirebaseModule::class, MapProviderModule::class, ), dynamicModuleKey = arrayOf( "Feature1", "Feature2" ) ) interface ApplicationComponent
11. Solution?
12. Dagger Extensions
13. Why Anvil and Hilt? What do they bring to the table? Inverse the relation between Component and Module
14. Anvil
15. Anvil Application Base Feature1 Define shared scopes Define shared abstractions Define feature scope & component Module to contribute ApplicationComponent Create ApplicationComponent * Binding for components
16. Anvil Base @Scope @MustBeDocumented @Retention annotation class ApplicationScope data class Feature( val title: String, val deeplinkHost: String ) interface FeatureDependencyProvider { fun <T> dependencies(): T } interface ApplicationPlugin { fun apply(application: Application) }
17. Anvil Base @ContributesTo(ApplicationScope::class) @Module class BaseModule { @Provides @ElementsIntoSet fun provideFeatureSet(): Set<Feature> = emptySet() @Provides @ElementsIntoSet fun provideApplicationPluginSet(): Set<ApplicationPlugin> = emptySet() }
18. Anvil Feature 1 @Scope @MustBeDocumented @Retention annotation class Feature1Scope @ContributesTo(ApplicationScope::class) interface Feature1Dependencies { fun sampleSharedLogger(): SampleSharedLogger fun depsWithAppLifecycle(): DepsWithAppLifecycle }
19. Anvil Feature 1 @Feature1Scope @MergeComponent( scope = Feature1Scope::class, dependencies = [Feature1Dependencies::class] ) interface Feature1Component
20. Anvil Feature 1 @ContributesTo(ApplicationScope::class) @Module class Feature1ModuleToApplication { // ... }
21. Anvil Feature 1 @ContributesTo(ApplicationScope::class) @Module class Feature1ModuleToApplication { @Provides @IntoSet fun provideFeature1(): Feature = Feature( "Feature 1", "feature1" ) }
22. Anvil Feature 1 @ContributesTo(ApplicationScope::class) @Module class Feature1ModuleToApplication { @Provides @IntoSet fun provideFeature1ApplicationPlugin(): ApplicationPlugin = Feature1ApplicationPlugin() }
23. Anvil Feature 1 @ContributesTo(ApplicationScope::class) @Module class Feature1ModuleToApplication { @Provides @ApplicationScope fun provideDepsWithAppLifecycle(application: Application): DepsWithAppLifecycle = DepsWithAppLifecycle(application) }
24. Anvil Application @ApplicationScope @MergeComponent(scope = ApplicationScope::class) interface ApplicationComponent
25. Anvil Generated @Component( modules = { Feature1ModuleToApplication.class, Feature2ModuleToApplication.class, BaseModule.class }, dependencies = {}) @ApplicationScope public abstract interface ApplicationComponent extends Feature1Dependencies, Feature2Dependencies { your_module/build/tmp/kapt3/stubs/...
26. Anvil Application class SampleApplication : Application() { // ... }
27. Anvil Application class SampleApplication : Application() { val applicationComponent = lazy { DaggerApplicationComponent.builder() .application(this) .build() } }
28. Anvil Application class SampleApplication : Application() { @Inject lateinit var applicationPlugins: Set<@JvmSuppressWildcards ApplicationPlugin> override fun onCreate() { super.onCreate() applicationComponent.value.inject(this) applicationPlugins.forEach { it.apply(this) } } }
29. Anvil Application class SampleApplication : Application(), FeatureDependencyProvider { @Suppress("UNCHECKED_CAST") override fun <T> dependencies(): T { return applicationComponent.value as? T ?: throw IllegalStateException( "Feature does not provide" + " its dependencies to the ApplicationScope.") } }
30. Hilt
31. Hilt Application Base Feature1 Define shared abstractions Module to contribute ApplicationComponent Add HiltAndroidApp annotation
32. Hilt Base data class Feature( val title: String, val deeplinkHost: String ) interface ApplicationPlugin { fun apply(application: Application) }
33. Hilt Base @InstallIn(ApplicationComponent::class) @Module class BaseModule { @Provides @ElementsIntoSet fun provideFeatureSet(): Set<Feature> = emptySet() @Provides @ElementsIntoSet fun provideApplicationPluginSet(): Set<ApplicationPlugin> = emptySet() }
34. Hilt Feature 1 @InstallIn(ApplicationComponent::class) @Module class Feature1ModuleToApplication { @Provides @IntoSet fun provideFeature1(): Feature = Feature( "Feature 1", "feature1" ) }
35. Hilt Feature 1 @InstallIn(ApplicationComponent::class) @Module class Feature1ModuleToApplication { @Provides @IntoSet fun provideFeature1ApplicationPlugin(): ApplicationPlugin = Feature1ApplicationPlugin() }
36. Hilt Feature 1 @InstallIn(ApplicationComponent::class) @Module class Feature1ModuleToApplication { @Provides @Singleton fun provideDepsWithAppLifecycle(application: Application): DepsWithAppLifecycle = DepsWithAppLifecycle(application) }
37. Hilt Application @HiltAndroidApp class SampleApplication : Application() { @Inject lateinit var applicationPlugins: Set<@JvmSuppressWildcards ApplicationPlugin> override fun onCreate() { super.onCreate() applicationPlugins.forEach { it.apply(this) } } }
38. A new perspective for Dagger by the Extensions
39. Thank you! • “Modularise in Structure” - 2019 https://bit.ly/3nBbslG • “Building Features by Independent Dagger Components” - 2018 https://bit.ly/36TsXba • About the ApplicationPlugin implementation https://bit.ly/3129aCx • Github repo for the sample application https://github.com/yayaa/IndependentFeatures @yahyabayramoglu