Dagger 2 - Under the hood

A look at Dagger's generated code and how it enables scoping to work.

Transcript

1. DAGGER 2 WHAT’S REALLY GOING ON HERE?
2. QUICK RECAP WHAT IS DEPENDENCY INJECTION? ▸ The idea that objects should have their dependencies provided to them, not create them on their own. Good: class RepoRepository(private val service: RepoService) Bad: class RepoRepository() { private val service = RepoService() }
3. QUICK RECAP WHAT IS A DEPENDENCY INJECTION FRAMEWORK? ▸ A library that assists the developer with providing dependencies to core application objects class RepoRepository @Inject constructor(private val service: RepoService)
4. Dagger is an example of over-engineering— it’s too complicated for what you get out of it -Developer who hasn’t seen the light
5. DAGGER 2 Components Hold all dependencies for a given scope
6. DAGGER 2 Components Hold all dependencies for a given scope Module Module Module Define how to create dependencies
7. DAGGER 2 Components Hold all dependencies for a given scope Module Module Module Define how to create dependencies
8. DAGGER 2 - SCOPES @Singleton
9. DAGGER 2 - SCOPES @Singleton @Component interface ApplicationComponent
10. DAGGER 2 - SCOPES @Singleton @Component interface ApplicationComponent Application Module Network Module Database Module
11. DAGGER 2 - SCOPES @Singleton @Component interface ApplicationComponent Application Module Network Module Database Module @ActivityScope @Subcomponent interface MyActivityComponent Navigation Module Permission Module
12. DAGGER 2 - SCOPES @Singleton @Component interface ApplicationComponent Application Module Network Module Database Module @ActivityScope @Subcomponent interface MyActivityComponent Navigation Module Permission Module @ScreenScope @Subcomponent interface ScreenOneComponent List Item Renderer Module Lifecycle Task Module
13. DAGGER 2 - SCOPES @ScreenScope @Subcomponent interface ScreenOneComponent List Item Renderer Module Lifecycle Task Module @ScreenScope @Subcomponent interface ScreenTwoComponent @Singleton @Component interface ApplicationComponent Application Module Network Module Database Module @ActivityScope @Subcomponent interface MyActivityComponent Navigation Module Permission Module Screen2 Endpoint Module Lifecycle Task Module
14. DAGGER 2 - BUILD TYPE SPECIFIC DEPENDENCIES DEBUG VS. RELEASE BUILDS @Singleton @Component(modules = { AndroidSupportInjectionModule.class, ApplicationModule.class, ActivityBindingModule.class, NetworkModule.class, ServiceModule.class, }) public interface ApplicationComponent extends AndroidInjector<MyApplication> { }
15. DAGGER 2 - BUILD TYPE SPECIFIC DEPENDENCIES DEBUG VS. RELEASE BUILDS @Module public abstract class NetworkModule { @Provides @Named("base_url") static String provideBaseUrl() { return “https://api.debug.mydomain.com/“; } @Provides @Singleton static Call.Factory provideCallFactory() { return new OkHttpClient.Builder() .addNetworkInterceptor(new StethoInterceptor()) .addInterceptor(new LoggingInterceptor()) .build(); } } @Module public abstract class NetworkModule { @Provides @Named("base_url") static String provideBaseUrl() { return “https://api.mydomain.com/"; } @Provides @Singleton static Call.Factory provideCallFactory() { return new OkHttpClient.Builder() .build(); } } Debug Release
16. DAGGER 2 - TEST SPECIFIC DEPENDENCIES TEST VS. STANDARD BUILDS @Module public abstract class TestServiceModule { @Binds abstract RepoService provideRepoService(TestRepoService service); } @Module public abstract class ServiceModule { @Provides @Singleton static RepoService provideRepoService(Retrofit retrofit) { return retrofit.create(RepoService.class); } } androidTest main @Singleton @Component(modules = { AndroidSupportInjectionModule.class, ActivityBindingModule.class, ApplicationModule.class, TestServiceModule.class, TestNetworkModule.class, }) public interface TestApplicationComponent extends ApplicationComponent { void inject(RepoListFragmentTest repoListFragmentTest); } @Singleton @Component(modules = { AndroidSupportInjectionModule.class, ApplicationModule.class, ActivityBindingModule.class, NetworkModule.class, ServiceModule.class, }) public interface ApplicationComponent extends AndroidInjector<MyApplication> { }
17. DAGGER 2 - BUILDING SCOPES Application @Singleton @Component ApplicationComponent Map of Activity Component Builders Activity @ActivityScope @Subcomponent MainActivityComponent Map of Screen Component Builders FragmentOne @ScreenScope @Subcomponent ScreenOneComponent FragmentTwo @ScreenScope @Subcomponent ScreenTwoComponent
18. DAGGER 2 - BUILDING SCOPES @Singleton @Component(modules = { AndroidSupportInjectionModule.class, ApplicationModule.class, ActivityBindingModule.class, NetworkModule.class, ServiceModule.class, }) public interface ApplicationComponent extends AndroidInjector<MyApplication> { }
19. DAGGER 2 - BUILDING SCOPES public class MyApplication extends DaggerApplication { protected ApplicationComponent component; @Override public void onCreate() { super.onCreate(); component = initComponent(); if (BuildConfig.DEBUG) { Timber.plant(new Timber.DebugTree()); } } protected ApplicationComponent initComponent() { return DaggerApplicationComponent.builder() .applicationModule(new ApplicationModule(this)) .build(); } @Override protected AndroidInjector<? extends DaggerApplication> applicationInjector() { return component; } }
20. DAGGER 2 - BUILDING SCOPES @ActivityScope @Subcomponent(modules = MainActivityModule.class) public interface MainActivityComponent extends AndroidInjector<MainActivity> { @Subcomponent.Builder abstract class Builder extends AndroidInjector.Builder<MainActivity> { } }
21. DAGGER 2 - BUILDING SCOPES @Module(subcomponents = MainActivityComponent.class) public abstract class ActivityBindingModule_MainActivity { @Binds @IntoMap @ActivityKey(MainActivity.class) abstract AndroidInjector.Factory<? extends Activity> bindAndroidInjectorFactory(MainActivitySubcomponent.Builder builder); }
22. DAGGER 2 - BUILDING SCOPES @ScreenScope @Subcomponent(modules = ScreenModule.class) public interface RepoDetailComponent extends AndroidInjector<RepoDetailFragment> { @Subcomponent.Builder abstract class Builder extends AndroidInjector.Builder<RepoDetailFragment> { @BindsInstance public abstract void bindOwner(@Named("owner") String owner); @BindsInstance public abstract void bindRepoName(@Named("repo") String repo); @Override public void seedInstance(RepoDetailFragment repoDetailFragment) { bindOwner(repoDetailFragment.getArguments().getString(RepoDetailFragment.OWNER_KEY)); bindRepoName(repoDetailFragment.getArguments().getString(RepoDetailFragment.REPO_KEY)); } } }
23. DAGGER 2 - BUILDING SCOPES @ScreenScope @Subcomponent(modules = ScreenModule.class) public interface RepoDetailComponent extends AndroidInjector<RepoDetailFragment> { @Subcomponent.Builder abstract class Builder extends AndroidInjector.Builder<RepoDetailFragment> { @BindsInstance public abstract void bindOwner(@Named("owner") String owner); @BindsInstance public abstract void bindRepoName(@Named("repo") String repo); @Override public void seedInstance(RepoDetailFragment repoDetailFragment) { bindOwner(repoDetailFragment.getArguments().getString(RepoDetailFragment.OWNER_KEY)); bindRepoName(repoDetailFragment.getArguments().getString(RepoDetailFragment.REPO_KEY)); } } }
24. DAGGER 2 - BUILDING SCOPES @ScreenScope @Subcomponent(modules = ScreenModule.class) public interface RepoDetailComponent extends AndroidInjector<RepoDetailFragment> { @Subcomponent.Builder abstract class Builder extends AndroidInjector.Builder<RepoDetailFragment> { @BindsInstance public abstract void bindOwner(@Named("owner") String owner); @BindsInstance public abstract void bindRepoName(@Named("repo") String repo); @Override public void seedInstance(RepoDetailFragment repoDetailFragment) { bindOwner(repoDetailFragment.getArguments().getString(RepoDetailFragment.OWNER_KEY)); bindRepoName(repoDetailFragment.getArguments().getString(RepoDetailFragment.REPO_KEY)); } } }
25. DAGGER 2 - BUILDING SCOPES @ScreenScope @Subcomponent(modules = ScreenModule.class) public interface RepoDetailComponent extends AndroidInjector<RepoDetailFragment> { @Subcomponent.Builder abstract class Builder extends AndroidInjector.Builder<RepoDetailFragment> { @BindsInstance public abstract void bindOwner(@Named("owner") String owner); @BindsInstance public abstract void bindRepoName(@Named("repo") String repo); @Override public void seedInstance(RepoDetailFragment repoDetailFragment) { bindOwner(repoDetailFragment.getArguments().getString(RepoDetailFragment.OWNER_KEY)); bindRepoName(repoDetailFragment.getArguments().getString(RepoDetailFragment.REPO_KEY)); } } }
26. DAGGER 2 - BUILDING SCOPES @ScreenScope @Subcomponent(modules = ScreenModule.class) public interface RepoDetailComponent extends AndroidInjector<RepoDetailFragment> { @Subcomponent.Builder abstract class Builder extends AndroidInjector.Builder<RepoDetailFragment> { @BindsInstance public abstract void bindOwner(@Named("owner") String owner); @BindsInstance public abstract void bindRepoName(@Named("repo") String repo); @Override public void seedInstance(RepoDetailFragment repoDetailFragment) { bindOwner(repoDetailFragment.getArguments().getString(RepoDetailFragment.OWNER_KEY)); bindRepoName(repoDetailFragment.getArguments().getString(RepoDetailFragment.REPO_KEY)); } } }
27. DAGGER 2 - BUILDING SCOPES @Module(subcomponents = RepoDetailComponent.class) public abstract class MainScreenBindingModule { @ScreenScope @ContributesAndroidInjector(modules = ScreenModule.class) abstract RepoListFragment repoListFragment(); @Binds @IntoMap @FragmentKey(RepoDetailFragment.class) abstract AndroidInjector.Factory<? extends Fragment> bindDetailInjector(RepoDetailComponent.Builder injectorBuilder); }
28. DAGGER 2 - BUILDING SCOPES @Module(subcomponents = RepoDetailComponent.class) public abstract class MainScreenBindingModule { @ScreenScope @ContributesAndroidInjector(modules = ScreenModule.class) abstract RepoListFragment repoListFragment(); @Binds @IntoMap @FragmentKey(RepoDetailFragment.class) abstract AndroidInjector.Factory<? extends Fragment> bindDetailInjector(RepoDetailComponent.Builder injectorBuilder); }
29. DAGGER 2 - BUILDING SCOPES @Module(subcomponents = RepoDetailComponent.class) public abstract class MainScreenBindingModule { @ScreenScope @ContributesAndroidInjector(modules = ScreenModule.class) abstract RepoListFragment repoListFragment(); @Binds @IntoMap @FragmentKey(RepoDetailFragment.class) abstract AndroidInjector.Factory<? extends Fragment> bindDetailInjector(RepoDetailComponent.Builder injectorBuilder); }
30. DAGGER 2 - SCOPES @ScreenScope final class RepoDetailPresenter { @Inject RepoDetailPresenter( @Named("owner") String owner, @Named("repo") String repoName, RepoRepository repoRepository, @ForScreen DisposableManager disposableManager, RepoDetailViewModel viewModel ) { disposableManager.add(repoRepository.getRepo(owner, repoName) .observeOn(AndroidSchedulers.mainThread()) .doOnSuccess(viewModel::processRepo) .observeOn(Schedulers.io()) .flatMap(repo -> repoRepository.getContributors(repo.getContributorsUrl())) .observeOn(AndroidSchedulers.mainThread()) .subscribe(viewModel::processContributors)); } }
31. DAGGER 2 - SCOPES @ScreenScope final class RepoDetailPresenter { @Inject RepoDetailPresenter( @Named("owner") String owner, @Named("repo") String repoName, RepoRepository repoRepository, @ForScreen DisposableManager disposableManager, RepoDetailViewModel viewModel ) { disposableManager.add(repoRepository.getRepo(owner, repoName) .observeOn(AndroidSchedulers.mainThread()) .doOnSuccess(viewModel::processRepo) .observeOn(Schedulers.io()) .flatMap(repo -> repoRepository.getContributors(repo.getContributorsUrl())) .observeOn(AndroidSchedulers.mainThread()) .subscribe(viewModel::processContributors)); } }
32. DAGGER 2 - SCOPES @ScreenScope final class RepoDetailPresenter { @Inject RepoDetailPresenter( @Named("owner") String owner, @Named("repo") String repoName, RepoRepository repoRepository, @ForScreen DisposableManager disposableManager, RepoDetailViewModel viewModel ) { disposableManager.add(repoRepository.getRepo(owner, repoName) .observeOn(AndroidSchedulers.mainThread()) .doOnSuccess(viewModel::processRepo) .observeOn(Schedulers.io()) .flatMap(repo -> repoRepository.getContributors(repo.getContributorsUrl())) .observeOn(AndroidSchedulers.mainThread()) .subscribe(viewModel::processContributors)); } }
33. DAGGER 2 - SCOPES @ScreenScope final class RepoDetailPresenter { @Inject RepoDetailPresenter( @Named("owner") String owner, @Named("repo") String repoName, RepoRepository repoRepository, @ForScreen DisposableManager disposableManager, RepoDetailViewModel viewModel ) { disposableManager.add(repoRepository.getRepo(owner, repoName) .observeOn(AndroidSchedulers.mainThread()) .doOnSuccess(viewModel::processRepo) .observeOn(Schedulers.io()) .flatMap(repo -> repoRepository.getContributors(repo.getContributorsUrl())) .observeOn(AndroidSchedulers.mainThread()) .subscribe(viewModel::processContributors)); } }
34. DAGGER 2 - SCOPES private final class RepoDetailComponentImpl implements RepoDetailComponent { /** Fields **/ private RepoDetailComponentImpl(RepoDetailComponentBuilder builder) { assert builder != null; initialize(builder); } private void initialize(final RepoDetailComponentBuilder builder) { this.provideScopeSubjectProvider = DoubleCheck.provider(ScreenModule_ProvideScopeSubjectFactory.create()); this.provideDisposableManagerProvider = DoubleCheck.provider( ScreenModule_ProvideDisposableManagerFactory.create(provideScopeSubjectProvider)); this.repoDetailViewModelProvider = DoubleCheck.provider(RepoDetailViewModel_Factory.create()); this.bindOwnerProvider = InstanceFactory.create(builder.bindOwner); this.bindRepoNameProvider = InstanceFactory.create(builder.bindRepoName); this.repoDetailPresenterProvider = DoubleCheck.provider( RepoDetailPresenter_Factory.create( bindOwnerProvider, bindRepoNameProvider, DaggerApplicationComponent.this.repoRepositoryProvider, provideDisposableManagerProvider, repoDetailViewModelProvider)); this.repoDetailFragmentMembersInjector = RepoDetailFragment_MembersInjector.create( MainActivitySubcomponentImpl.this.dispatchingAndroidInjectorProvider, provideScopeSubjectProvider, provideDisposableManagerProvider, repoDetailViewModelProvider, repoDetailPresenterProvider); } @Override public void inject(RepoDetailFragment arg0) { repoDetailFragmentMembersInjector.injectMembers(arg0); } }
35. DAGGER 2 - SCOPES private void initialize(final RepoDetailComponentBuilder builder) { this.provideScopeSubjectProvider = DoubleCheck.provider(ScreenModule_ProvideScopeSubjectFactory.create()); this.provideDisposableManagerProvider = DoubleCheck.provider( ScreenModule_ProvideDisposableManagerFactory.create(provideScopeSubjectProvider)); this.repoDetailViewModelProvider = DoubleCheck.provider(RepoDetailViewModel_Factory.create()); this.bindOwnerProvider = InstanceFactory.create(builder.bindOwner); this.bindRepoNameProvider = InstanceFactory.create(builder.bindRepoName); this.repoDetailPresenterProvider = DoubleCheck.provider( RepoDetailPresenter_Factory.create( bindOwnerProvider, bindRepoNameProvider, DaggerApplicationComponent.this.repoRepositoryProvider, provideDisposableManagerProvider, repoDetailViewModelProvider)); this.repoDetailFragmentMembersInjector = RepoDetailFragment_MembersInjector.create( MainActivitySubcomponentImpl.this.dispatchingAndroidInjectorProvider, provideScopeSubjectProvider, provideDisposableManagerProvider, repoDetailViewModelProvider, repoDetailPresenterProvider); }
36. DAGGER 2 - SCOPES private void initialize(final RepoDetailComponentBuilder builder) { this.provideScopeSubjectProvider = DoubleCheck.provider(ScreenModule_ProvideScopeSubjectFactory.create()); this.provideDisposableManagerProvider = DoubleCheck.provider( ScreenModule_ProvideDisposableManagerFactory.create(provideScopeSubjectProvider)); this.repoDetailViewModelProvider = DoubleCheck.provider(RepoDetailViewModel_Factory.create()); this.bindOwnerProvider = InstanceFactory.create(builder.bindOwner); this.bindRepoNameProvider = InstanceFactory.create(builder.bindRepoName); this.repoDetailPresenterProvider = DoubleCheck.provider( RepoDetailPresenter_Factory.create( bindOwnerProvider, bindRepoNameProvider, DaggerApplicationComponent.this.repoRepositoryProvider, provideDisposableManagerProvider, repoDetailViewModelProvider)); this.repoDetailFragmentMembersInjector = RepoDetailFragment_MembersInjector.create( MainActivitySubcomponentImpl.this.dispatchingAndroidInjectorProvider, provideScopeSubjectProvider, provideDisposableManagerProvider, repoDetailViewModelProvider, repoDetailPresenterProvider); }
37. DAGGER 2 - SCOPES public final class InstanceFactory<T> implements Factory<T>, Lazy<T> { public static <T> Factory<T> create(T instance) { return new InstanceFactory<T>(checkNotNull(instance, "instance cannot be null")); } private final T instance; private InstanceFactory(T instance) { this.instance = instance; } @Override public T get() { return instance; } }
38. DAGGER 2 - SCOPES private void initialize(final RepoDetailComponentBuilder builder) { this.provideScopeSubjectProvider = DoubleCheck.provider(ScreenModule_ProvideScopeSubjectFactory.create()); this.provideDisposableManagerProvider = DoubleCheck.provider( ScreenModule_ProvideDisposableManagerFactory.create(provideScopeSubjectProvider)); this.repoDetailViewModelProvider = DoubleCheck.provider(RepoDetailViewModel_Factory.create()); this.bindOwnerProvider = InstanceFactory.create(builder.bindOwner); this.bindRepoNameProvider = InstanceFactory.create(builder.bindRepoName); this.repoDetailPresenterProvider = DoubleCheck.provider( RepoDetailPresenter_Factory.create( bindOwnerProvider, bindRepoNameProvider, DaggerApplicationComponent.this.repoRepositoryProvider, provideDisposableManagerProvider, repoDetailViewModelProvider)); this.repoDetailFragmentMembersInjector = RepoDetailFragment_MembersInjector.create( MainActivitySubcomponentImpl.this.dispatchingAndroidInjectorProvider, provideScopeSubjectProvider, provideDisposableManagerProvider, repoDetailViewModelProvider, repoDetailPresenterProvider); }
39. DAGGER 2 - SCOPES public final class RepoDetailPresenter_Factory implements Factory<RepoDetailPresenter> { /* Fields */ public RepoDetailPresenter_Factory(…) { /…/ } @Override public RepoDetailPresenter get() { return new RepoDetailPresenter( ownerProvider.get(), repoNameProvider.get(), repoRepositoryProvider.get(), disposableManagerProvider.get(), viewModelProvider.get()); } public static Factory<RepoDetailPresenter> create(…) { return new RepoDetailPresenter_Factory(…); } }
40. DAGGER 2 - SCOPES public final class RepoDetailPresenter_Factory implements Factory<RepoDetailPresenter> { /* Fields */ public RepoDetailPresenter_Factory(…) { /…/ } @Override public RepoDetailPresenter get() { return new RepoDetailPresenter( ownerProvider.get(), repoNameProvider.get(), repoRepositoryProvider.get(), disposableManagerProvider.get(), viewModelProvider.get()); } public static Factory<RepoDetailPresenter> create(…) { return new RepoDetailPresenter_Factory(…); } }
41. DAGGER 2 - SCOPES public T get() { Object result = instance; if (result == UNINITIALIZED) { synchronized (this) { result = instance; if (result == UNINITIALIZED) { result = provider.get(); /* */ instance = result; /* Null out the reference to the provider. We are never going to need it again, so we * can make it eligible for GC. */ provider = null; } } } return (T) result; }
42. LINKS Sample Application: https://github.com/bgogetap/GDG-Omaha-GitHub-Browser Dagger Stuff: Gregory Kick - Understanding Dagger 2's Codegen https://www.youtube.com/watch?v=-UWWFBEhW3Q