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🗡 Demystifying Dagger Ryan Harter Mobile Summit 2023

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The Grid Graph

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Backend Property CrashReporter 🗡

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Backend Property CrashReporter 🗡

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Property CrashReporter API Key HttpClient Backend 🗡

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Property CrashReporter API Key HttpClient Backend 🗡

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Property CrashReporter API Key HttpClient Backend The Graph 🗡

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Dependency Injection 🗡

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Dependency Injection 🗡 class CrashReporter Property("awesome") Backend(token = "abc123") private val userProp: Property private val backend: Backend = = { / / . .. }

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Dependency Injection 🗡 class CrashReporter private val userProp: Property private val backend: Backend = = { / / . .. } MyDependencies.property MyDependencies.backend

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Dependency Injection 🗡 class CrashReporter private val userProp: Property private val backend: Backend = = { / / . .. } get() get()

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Dependency Injection 🗡 class CrashReporter private val userProp: Property private val backend: Backend / / . .. } ( , , { )

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javax.inject 🗡

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javax.inject 🗡 Provide

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javax.inject 🗡 Provider

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javax.inject 🗡 interface Provider { fun get(): T }

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Injection • Constructor Injection • Member Injection • Provider Injection 🗡

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Constructor Injection 🗡

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class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) { // . .. } @Inject constructor userProp: Property backend: Backend Constructor Injection 🗡

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class CrashReporter @Inject constructor(

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class CrashReporter @Inject constructor(

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class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) { // . .. } @Inject constructor userProp: Property backend: Backend Constructor Injection 🗡

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class CrashReporter_Factory( private val userPropProvider: Provider, private val backendProvider: Provider, ) : Provider { override fun get(): CrashReporter { return CrashReporter( userPropProvider.get(), backendProvider.get(), ) } } CrashReporter_Factory userPropProvider: Provider backendProvider: Provider Provider override fun get(): CrashReporter CrashReporter( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡

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class CrashReporter_Factory(

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class CrashReporter_Factory(

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class CrashReporter_Factory(

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class CrashReporter_Factory(

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class CrashReporter_Factory( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡

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class CrashReporter_Factory( private val userPropProvider: Provider, private val backendProvider: Provider, ) : Provider { override fun get(): CrashReporter { return CrashReporter( userPropProvider.get(), backendProvider.get(), ) } } CrashReporter_Factory userPropProvider: Provider backendProvider: Provider Provider override fun get(): CrashReporter CrashReporter( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡

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Member Injection 🗡

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interface MembersInjector { fun injectMembers(instance: T) } Member Injection 🗡

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class MyFragment : Fragment() { @Inject lateinit var crashReporter: CrashReporter } Member Injection 🗡

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class MyFragment_MembersInjector( private val crashReporterProvider: Provider, ) : MembersInjector { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector private val crashReporterProvider: Provider override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡

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class MyFragment_MembersInjector(

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class MyFragment_MembersInjector(

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class MyFragment_MembersInjector(

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class MyFragment_MembersInjector(

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class MyFragment_MembersInjector(

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class MyFragment_MembersInjector(

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class MyFragment_MembersInjector( private val crashReporterProvider: Provider, ) : MembersInjector { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector private val crashReporterProvider: Provider override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡

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Provider Injection 🗡

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@Module class CrashModule { @Provides fun provideBackend(token: ApiToken): Backend { return Backend(token) } } @Module class CrashModule { @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) Provider Injection 🗡

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@Module

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@Module

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@Module

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@Module

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@Module

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@Module

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@Module

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@Module class CrashModule { @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } Provider Injection 🗡

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@Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract Provider Injection 🗡

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@Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract Provider Injection 🗡

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@Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract @Binds Provider Injection 🗡

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@Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract @Binds abstract fun bindService() Provider Injection 🗡

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@Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract @Binds abstract fun bindService(backend: Backend) Provider Injection 🗡

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@Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract @Binds abstract fun bindService(backend: Backend): Service Provider Injection 🗡

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{ { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider Provider : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡

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{ { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider Provider : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡

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{ { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider Provider : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡

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{ { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider Provider : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡

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{ { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider Provider : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡

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{ { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider Provider : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡

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{ { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider Provider : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡

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{ { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider Provider : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡

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{ { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider Provider : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡

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Qualifiers 🗡

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class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) Property Backend Qualifiers 🗡

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class CrashReporter @Inject constructor(

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class CrashReporter @Inject constructor( @Inject lateinit var crashReporter: CrashReporter } Property Backend CrashReporter Qualifiers 🗡

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class CrashReporter @Inject constructor(

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class CrashModule { @Provides fun provideBackend(token: ApiToken): Backend { return Backend(token) } } class MyFragment : Fragment() {

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@Module class CrashModule { } @Provides return Backend(token) } ): Backend { ApiToken String Qualifiers 🗡 fun provideBackend(token:

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@Module class CrashModule { } @Provides return Backend(token) } ): Backend { ApiToken String Qualifiers 🗡 fun provideBackend(token:

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@Module

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@Module

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@Module

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@Module

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@Module

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@Module class CrashModule { } @Provides return Backend(token) } ): Backend { String @Provides fun provideApiToken(): String = "abcd" @ApiToken fun provideBackend( token: @ApiToken Qualifiers 🗡

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Property CrashReporter API Key HttpClient Backend The Graph

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Component

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@Component(modules = [CrashModule :: class]) interface AppComponent class DaggerAppComponent {

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class DaggerAppComponent { DaggerAppComponent companion object { fun builder(): Builder { // .. . } } class Builder { // ... fun build(): AppComponent { // .. . } } private class AppComponentImpl : AppComponent { // .

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class DaggerAppComponent { DaggerAppComponent companion object { .

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class DaggerAppComponent { DaggerAppComponent companion object { fun builder(): Builder { // .. . } } class Builder { // ... fun build(): AppComponent { // .. . } } private class AppComponentImpl : AppComponent { .

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class DaggerAppComponent { DaggerAppComponent companion object { / / . ..

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class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { .

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class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { // Providers private val userPropProvider: Provider private val backendProvider: Provider private val tokenProvider: Provider private val crashReporterProvider: Provider // MembersInjectors private val myFragmentMembersInjector: MembersInjector } } .

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@Component(modules = [CrashModule :: class]) interface AppComponent { } fun inject(instance: MyFragment)

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@Component(modules = [CrashModule

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class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { // Providers private val userPropProvider: Provider private val backendProvider: Provider private val tokenProvider: Provider private val crashReporterProvider: Provider // MembersInjectors private val myFragmentMembersInjector: MembersInjector } } .

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class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { myFragmentMembersInjector.injectMembers(instance) }

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@Component(modules = [CrashModule :: class]) interface AppComponent { } fun inject(instance: MyFragment)

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@Component(modules = [CrashModule

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class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { // Providers private val userPropProvider: Provider private val backendProvider: Provider private val tokenProvider: Provider private val crashReporterProvider: Provider // MembersInjectors private val myFragmentMembersInjector: MembersInjector } } myFragmentMembersInjector.injectMembers(instance) }

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private class AppComponentImpl : AppComponent { get() = crashReporterProvider.get()

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@Component(modules = [CrashModule :: class]) interface AppComponent { } fun inject(instance: MyFragment) val crashReporter: CrashReporter

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@Component(modules = [CrashModule

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@Component(modules = [CrashModule

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@Component(modules = [CrashModule

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class ScopedProvider( private val implProvider: Provider ) : Provider { private var instance: T? = null override fun get(): T { if (instance = = null) { instance = implProvider.get() } return instance } }

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private class AppComponentImpl : AppComponent { // Providers private val userPropProvider: Provider private val backendProvider: Provider private val tokenProvider: Provider private val crashReporterProvider: Provider // MembersInjectors private val myFragmentMembersInjector: MembersInjector } } myFragmentMembersInjector.injectMembers(instance) } override val crashReporter: CrashReporter get() = crashReporterProvider.get()

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private class AppComponentImpl : AppComponent { // . .. , crashReporterProvider: Provider, ) { // . .. this.crashReporterProvider = } crashReporterProvider

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private class AppComponentImpl : AppComponent { // . .. , crashReporterProvider: Provider, ) { // . .. this.crashReporterProvider = } ScopedProvider(crashReporterProvider) crashReporterProvider

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AppComponent

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AppComponent @UserId +

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AppComponent @UserId + = UserComponent

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AppComponent + = UserComponent @UserId

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AppComponent + = UserComponent @UserId Subcomponent

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AppComponent + = UserComponent @UserId Subcomponent UserSubcomponent

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âš’ Anvil

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{ } fun inject(instance: MyFragment) { @Component(modules = [CrashModule :: class]) interface AppComponent âš’

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{ } fun inject(instance: MyFragment) fun inject(instance: ListActivity) fun inject(instance: ItemListFragment) fun inject(instance: ItemDetailFragment) fun inject(instance: ShareFragment) fun inject(instance: AccountActivity) fun inject(instance: FriendsFragment) fun inject(instance: SettingsActivity) @Component(modules = [CrashModule :: class]) interface AppComponent âš’

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{ } fun inject(instance: MyFragment) fun inject(instance: ListActivity) fun inject(instance: ItemListFragment) fun inject(instance: ItemDetailFragment) fun inject(instance: ShareFragment) fun inject(instance: AccountActivity) fun inject(instance: FriendsFragment) fun inject(instance: SettingsActivity) @Component(modules = [ CrashModule :: class ]) interface AppComponent , AnalyticsModule :: class, NetworkModule : : class BillingModule : : class DatabaseModule :: class FileModule :: class UserModule :: class , , , , , âš’

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@Component(modules = [ CrashModule :: class ]) interface AppComponent , AnalyticsModule :: class, NetworkModule : : class BillingModule : : class DatabaseModule :: class FileModule :: class UserModule :: class , , , , , âš’ : MyFragmentInjector, ListActivityInjector, ItemListFragmentInjector, ItemDetailFragmentInjector, ShareFragmentInjector, AccountActivityInjector, FriendsFragmentInjector, SettingsActivityInjector,

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âš’ abstract class AppScope

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âš’ abstract class AppObjectGraph

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âš’ abstract class AppObjectGraph interface MyFragmentInjector { fun inject(instance: MyFragment) }

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âš’ abstract class AppObjectGraph interface MyFragmentInjector { :: class)

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âš’ abstract class AppObjectGraph interface MyFragmentInjector { :

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âš’ abstract class AppObjectGraph interface MyFragmentInjector { :: class)

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@Component(modules = [ CrashModule :: class ]) interface AppComponent , AnalyticsModule :: class, NetworkModule : : class BillingModule : : class DatabaseModule :: class FileModule :: class UserModule :: class , , , , , âš’ : MyFragmentInjector, ListActivityInjector, ItemListFragmentInjector, ItemDetailFragmentInjector, ShareFragmentInjector, AccountActivityInjector, FriendsFragmentInjector, SettingsActivityInjector, @MergeComponent(scope = AppObjectGraph :

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interface AppComponent âš’ @MergeComponent(scope = AppObjectGraph :: class)

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âš’ class RealCrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ): CrashReporter { // . .. }

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âš’ @Module interface CrashModule { @Binds } fun bindCrashReporter(impl: RealCrashReporter): CrashReporter @ContributesTo(AppObjectGraph :: class) class RealCrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ): CrashReporter { // . .. }

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âš’ class RealCrashReporter @Inject constructor( :: class)

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âš’ Anvil

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⚒ Anvil Dagger 🗡 +

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🗡 Demystifying Dagger Ryan Harter Mobile Summit 2023