Demystifying Dagger

Dagger gets a bad rap for being "difficult to understand", or "overly complicated", or "black magic". In reality, Dagger generates pretty straight-forward, elegant wiring code similar to how we would likely write it manually and, I believe, it's the complexity of large scale apps that makes it complex.

In this talk we'll look at different types of injection that Dagger supports, and the code it generates to do so, to get an understanding of what it's doing and how it works. We'll then dive into Components and Subcomponents to see how Dagger wires together our dependencies into a graph. Finally, we'll look at how Dagger can be extended using Anvil and other tools.

Transcript

1. 🗡 Demystifying Dagger Ryan Harter @ryan@harter.us
2. Follow Along Ryan Harter @ryan@harter.us https://ryans.link/london-dagger
3. The Graph 🗡
4. Backend Property CrashReporter 🗡
5. Backend Property CrashReporter 🗡
6. Property CrashReporter API Key HttpClient Backend 🗡
7. Property CrashReporter API Key HttpClient Backend 🗡
8. Property CrashReporter API Key HttpClient Backend The Graph 🗡
9. Dependency Injection 🗡
10. Dependency Injection 🗡 class CrashReporter Property("awesome") Backend(token = "abc123") private val userProp: Property private val backend: Backend = = { / / . .. }
11. Dependency Injection 🗡 class CrashReporter private val userProp: Property private val backend: Backend = = { / / . .. } MyDependencies.property MyDependencies.backend
12. Dependency Injection 🗡 class CrashReporter private val userProp: Property private val backend: Backend = = { / / . .. } get() get()
13. Dependency Injection 🗡 class CrashReporter private val userProp: Property private val backend: Backend / / . .. } ( , , { )
14. javax.inject 🗡
15. javax.inject 🗡 Provide
16. javax.inject 🗡 Provider<T>
17. javax.inject 🗡 interface Provider<T> { fun get(): T }
18. Injection • Constructor Injection • Member Injection • Provider Injection 🗡
19. Constructor Injection 🗡
20. class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) { // . .. } @Inject constructor userProp: Property backend: Backend Constructor Injection 🗡
21. class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) { } @Inject constructor Constructor Injection 🗡
22. class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) { } @Inject constructor userProp: Property backend: Backend Constructor Injection 🗡
23. class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) { // . .. } @Inject constructor userProp: Property backend: Backend Constructor Injection 🗡
24. class CrashReporter_Factory( private val userPropProvider: Provider<Property>, private val backendProvider: Provider<Backend>, ) : Provider<CrashReporter> { override fun get(): CrashReporter { return CrashReporter( userPropProvider.get(), backendProvider.get(), ) } } CrashReporter_Factory userPropProvider: Provider<Property> backendProvider: Provider<Backend> Provider<CrashReporter> override fun get(): CrashReporter CrashReporter( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡
25. class CrashReporter_Factory( private val userPropProvider: Provider<Property>, private val backendProvider: Provider<Backend>, ) : Provider<CrashReporter> { override fun get(): CrashReporter { return CrashReporter( userPropProvider.get(), backendProvider.get(), ) } } CrashReporter_Factory userPropProvider: Provider<Property> backendProvider: Provider<Backend> Provider<CrashReporter> override fun get(): CrashReporter CrashReporter( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡
26. class CrashReporter_Factory( private val userPropProvider: Provider<Property>, private val backendProvider: Provider<Backend>, ) : Provider<CrashReporter> { override fun get(): CrashReporter { return CrashReporter( userPropProvider.get(), backendProvider.get(), ) } } CrashReporter_Factory userPropProvider: Provider<Property> backendProvider: Provider<Backend> Provider<CrashReporter> override fun get(): CrashReporter CrashReporter( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡
27. class CrashReporter_Factory( private val userPropProvider: Provider<Property>, private val backendProvider: Provider<Backend>, ) : Provider<CrashReporter> { override fun get(): CrashReporter { return CrashReporter( userPropProvider.get(), backendProvider.get(), ) } } CrashReporter_Factory userPropProvider: Provider<Property> backendProvider: Provider<Backend> Provider<CrashReporter> override fun get(): CrashReporter CrashReporter( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡
28. class CrashReporter_Factory( private val userPropProvider: Provider<Property>, private val backendProvider: Provider<Backend>, ) : Provider<CrashReporter> { override fun get(): CrashReporter { return CrashReporter( userPropProvider.get(), backendProvider.get(), ) } } CrashReporter_Factory private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> Provider<CrashReporter> override fun get(): CrashReporter CrashReporter( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡
29. class CrashReporter_Factory( private val userPropProvider: Provider<Property>, private val backendProvider: Provider<Backend>, ) : Provider<CrashReporter> { override fun get(): CrashReporter { return CrashReporter( userPropProvider.get(), backendProvider.get(), ) } } CrashReporter_Factory private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> Provider<CrashReporter> override fun get(): CrashReporter CrashReporter( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡
30. class CrashReporter_Factory( private val userPropProvider: Provider<Property>, private val backendProvider: Provider<Backend>, ) : Provider<CrashReporter> { override fun get(): CrashReporter { return CrashReporter( userPropProvider.get(), backendProvider.get(), ) } } CrashReporter_Factory userPropProvider: Provider<Property> backendProvider: Provider<Backend> Provider<CrashReporter> override fun get(): CrashReporter CrashReporter( userPropProvider.get(), backendProvider.get(), ) Constructor Injection 🗡
31. Member Injection 🗡
32. interface MembersInjector<T> { fun injectMembers(instance: T) } Member Injection 🗡
33. class MyFragment : Fragment() { @Inject lateinit var crashReporter: CrashReporter } Member Injection 🗡
34. class MyFragment_MembersInjector( private val crashReporterProvider: Provider<CrashReporter>, ) : MembersInjector<MyFragment> { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector<MyFragment> private val crashReporterProvider: Provider<CrashReporter> override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡
35. class MyFragment_MembersInjector( private val crashReporterProvider: Provider<CrashReporter>, ) : MembersInjector<MyFragment> { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector<MyFragment> private val crashReporterProvider: Provider<CrashReporter> override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡
36. class MyFragment_MembersInjector( private val crashReporterProvider: Provider<CrashReporter>, ) : MembersInjector<MyFragment> { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector<MyFragment> private val crashReporterProvider: Provider<CrashReporter> override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡
37. class MyFragment_MembersInjector( private val crashReporterProvider: Provider<CrashReporter>, ) : MembersInjector<MyFragment> { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector<MyFragment> private val crashReporterProvider: Provider<CrashReporter> override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡
38. class MyFragment_MembersInjector( private val crashReporterProvider: Provider<CrashReporter>, ) : MembersInjector<MyFragment> { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector<MyFragment> private val crashReporterProvider: Provider<CrashReporter> override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡
39. class MyFragment_MembersInjector( private val crashReporterProvider: Provider<CrashReporter>, ) : MembersInjector<MyFragment> { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector<MyFragment> private val crashReporterProvider: Provider<CrashReporter> override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡
40. class MyFragment_MembersInjector( private val crashReporterProvider: Provider<CrashReporter>, ) : MembersInjector<MyFragment> { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector<MyFragment> private val crashReporterProvider: Provider<CrashReporter> override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡
41. class MyFragment_MembersInjector( private val crashReporterProvider: Provider<CrashReporter>, ) : MembersInjector<MyFragment> { override fun injectMembers(instance: MyFragment) { instance.crashReporter = crashReporterProvider.get() } } MyFragment_MembersInjector MembersInjector<MyFragment> private val crashReporterProvider: Provider<CrashReporter> override fun injectMembers(instance: MyFragment) instance.crashReporter = crashReporterProvider.get() Member Injection 🗡
42. Provider Injection 🗡
43. @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 🗡
44. @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 🗡
45. @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 🗡
46. @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 🗡
47. @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 🗡
48. @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 🗡
49. @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 🗡
50. @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 🗡
51. @Module class CrashModule { @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } Provider Injection 🗡
52. @Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract Provider Injection 🗡
53. @Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract Provider Injection 🗡
54. @Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract @Binds Provider Injection 🗡
55. @Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract @Binds abstract fun bindService() Provider Injection 🗡
56. @Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract @Binds abstract fun bindService(backend: Backend) Provider Injection 🗡
57. @Module @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } class CrashModule { abstract @Binds abstract fun bindService(backend: Backend): Service Provider Injection 🗡
58. { { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider<ApiToken> Provider<Backend?> : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡
59. { { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider<ApiToken> Provider<Backend?> : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡
60. { { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider<ApiToken> Provider<Backend?> : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡
61. { { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider<ApiToken> Provider<Backend?> : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡
62. { { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider<ApiToken> Provider<Backend?> : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡
63. { { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider<ApiToken> Provider<Backend?> : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡
64. { { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider<ApiToken> Provider<Backend?> : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡
65. { { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider<ApiToken> Provider<Backend?> : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡
66. { { CrashModule_ProvideBackendFactory ) } } class ( private val module: CrashModule, , private val tokenProvider: Provider<ApiToken> Provider<Backend?> : override fun get(): Backend return module.provideBackend( ) tokenProvider.get() Provider Injection 🗡
67. Qualifiers 🗡
68. class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) Property Backend Qualifiers 🗡
69. class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) Property Backend Qualifiers 🗡
70. class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) class MyFragment : Fragment() { @Inject lateinit var crashReporter: CrashReporter } Property Backend CrashReporter Qualifiers 🗡
71. class CrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ) class MyFragment : Fragment() { @Inject lateinit var crashReporter: CrashReporter } Property Backend CrashReporter Qualifiers 🗡
72. private val backend: Backend, ) @Module class CrashModule { @Provides fun provideBackend(token: ApiToken): Backend { return Backend(token) } } class MyFragment : Fragment() { @Inject lateinit var crashReporter: CrashReporter } Backend CrashReporter Backend Qualifiers 🗡
73. private val backend: Backend, ) @Module class CrashModule { @Provides fun provideBackend(token: ApiToken): Backend { return Backend(token) } } class MyFragment : Fragment() { @Inject lateinit var crashReporter: CrashReporter } Backend CrashReporter Backend Qualifiers 🗡
74. @Module class CrashModule { } @Provides return Backend(token) } ): Backend { ApiToken String Qualifiers 🗡 fun provideBackend(token:
75. @Module class CrashModule { } @Provides return Backend(token) } ): Backend { ApiToken String Qualifiers 🗡 fun provideBackend(token:
76. @Module class CrashModule { } @Provides return Backend(token) } String Qualifiers 🗡 fun provideBackend(token: ): Backend {
77. @Module class CrashModule { } @Provides return Backend(token) } ): Backend { fun provideBackend( String @Provides fun provideApiToken(): String = "abcd" token: Qualifiers 🗡
78. @Module class CrashModule { } @Provides return Backend(token) } ): Backend { String @Provides fun provideApiToken(): String = "abcd" fun provideBackend(token: Qualifiers 🗡
79. @Module class CrashModule { } @Provides return Backend(token) } ): Backend { String @Provides fun provideApiToken(): String = "abcd" @ApiToken fun provideBackend( token: @ApiToken Qualifiers 🗡
80. @Module class CrashModule { } @Provides return Backend(token) } ): Backend { String @Provides fun provideApiToken(): String = "abcd" @ApiToken fun provideBackend( token: @ApiToken Qualifiers 🗡
81. The Graph
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95. Property CrashReporter API Key HttpClient Backend The Graph
96. Component
97. @Component(modules = [CrashModule :: class]) interface AppComponent class DaggerAppComponent { companion object { fun builder(): Builder {
99. class DaggerAppComponent { DaggerAppComponent companion object { fun builder(): Builder { // .. . } } class Builder { // ... fun build(): AppComponent { // .. . } } private class AppComponentImpl : AppComponent { // .
100. class DaggerAppComponent { DaggerAppComponent companion object { fun builder(): Builder { } } class Builder { fun build(): AppComponent { } } private class AppComponentImpl : AppComponent { .
101. class DaggerAppComponent { DaggerAppComponent companion object { fun builder(): Builder { // .. . } } class Builder { // ... fun build(): AppComponent { // .. . } } private class AppComponentImpl : AppComponent { .
102. class DaggerAppComponent { DaggerAppComponent companion object { fun builder(): Builder { } } class Builder { fun build(): AppComponent { } } private class AppComponentImpl : AppComponent { private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> private val myFragmentMembersInjector: MembersInjector<MyFragment> } } / / . ..
103. class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> private val myFragmentMembersInjector: MembersInjector<MyFragment> } } .
104. class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { // Providers private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> // MembersInjectors private val myFragmentMembersInjector: MembersInjector<MyFragment> } } .
105. @Component(modules = [CrashModule :: class]) interface AppComponent { } fun inject(instance: MyFragment)
106. @Component(modules = [CrashModule interface AppComponent { } fun inject(instance: MyFragment)
107. class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { // Providers private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> // MembersInjectors private val myFragmentMembersInjector: MembersInjector<MyFragment> } } .
108. class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> private val myFragmentMembersInjector: MembersInjector<MyFragment> } } . override fun inject(instance: MyFragment) { myFragmentMembersInjector.injectMembers(instance) }
109. @Component(modules = [CrashModule :: class]) interface AppComponent { } fun inject(instance: MyFragment)
110. @Component(modules = [CrashModule interface AppComponent { } fun inject(instance: MyFragment) val crashReporter: CrashReporter
111. class DaggerAppComponent { DaggerAppComponent private class AppComponentImpl : AppComponent { // Providers private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> // MembersInjectors private val myFragmentMembersInjector: MembersInjector<MyFragment> } } . override fun inject(instance: MyFragment) { myFragmentMembersInjector.injectMembers(instance) }
112. private class AppComponentImpl : AppComponent { private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> private val myFragmentMembersInjector: MembersInjector<MyFragment> } } . override fun inject(instance: MyFragment) { myFragmentMembersInjector.injectMembers(instance) } override val crashReporter: CrashReporter get() = crashReporterProvider.get()
113. @Component(modules = [CrashModule :: class]) interface AppComponent { } fun inject(instance: MyFragment) val crashReporter: CrashReporter
114. @Component(modules = [CrashModule interface AppComponent { } fun inject(instance: MyFragment) val crashReporter: CrashReporter @AppScope
115. @Component(modules = [CrashModule interface AppComponent { } fun inject(instance: MyFragment) val crashReporter: CrashReporter @AppScope @Module interface CrashModule { @Binds } fun bindCrashReporter(impl: RealCrashReporter): CrashReporter @AppScope
116. @Component(modules = [CrashModule interface AppComponent { } fun inject(instance: MyFragment) val crashReporter: CrashReporter @AppScope @Module interface CrashModule { @Binds } fun bindCrashReporter(impl: RealCrashReporter): CrashReporter @AppScope
117. class ScopedProvider<T>( ) : Provider<T> { override fun get(): T { return instance } } private val implProvider: Provider<T> private var instance: T? = null if (instance = = null) { instance = implProvider.get() }
118. class ScopedProvider<T>( ) : Provider<T> { override fun get(): T { return instance } } private val implProvider: Provider<T> private var instance: T? = null if (instance instance = implProvider.get() }
119. class ScopedProvider<T>( ) : Provider<T> { override fun get(): T { return instance } } private val implProvider: Provider<T> private var instance: T? = null if (instance instance = implProvider.get() }
120. class ScopedProvider<T>( ) : Provider<T> { override fun get(): T { return instance } } private val implProvider: Provider<T> private var instance: T? = null if (instance = = null) { instance = implProvider.get() }
121. private class AppComponentImpl : AppComponent { // Providers private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> // MembersInjectors private val myFragmentMembersInjector: MembersInjector<MyFragment> } } . override fun inject(instance: MyFragment) { myFragmentMembersInjector.injectMembers(instance) } override val crashReporter: CrashReporter get() = crashReporterProvider.get()
122. private class AppComponentImpl : AppComponent { private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> private val myFragmentMembersInjector: MembersInjector<MyFragment> . override fun inject(instance: MyFragment) { myFragmentMembersInjector.injectMembers(instance) } init( // . .. , crashReporterProvider: Provider<CrashReporter>, ) { // . .. this.crashReporterProvider = } crashReporterProvider
123. private class AppComponentImpl : AppComponent { private val userPropProvider: Provider<Property> private val backendProvider: Provider<Backend> private val tokenProvider: Provider<ApiToken> private val crashReporterProvider: Provider<CrashReporter> private val myFragmentMembersInjector: MembersInjector<MyFragment> . override fun inject(instance: MyFragment) { myFragmentMembersInjector.injectMembers(instance) } init( // . .. , crashReporterProvider: Provider<CrashReporter>, ) { // . .. this.crashReporterProvider = } ScopedProvider(crashReporterProvider) crashReporterProvider
124. AppComponent
125. AppComponent @UserId +
126. AppComponent @UserId + = UserComponent
127. AppComponent + = UserComponent @UserId
128. AppComponent + = UserComponent @UserId Subcomponent
129. AppComponent + = UserComponent @UserId Subcomponent UserSubcomponent
130. ⚒ Anvil
131. { } fun inject(instance: MyFragment) { @Component(modules = [CrashModule :: class]) interface AppComponent ⚒
132. { } 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 ⚒
133. { } 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 , , , , , ⚒
134. @Component(modules = [ CrashModule :: class ]) interface AppComponent , AnalyticsModule :: class, NetworkModule : : class BillingModule : : class DatabaseModule :: class FileModule :: class UserModule :: class , , , , , ⚒ : MyFragmentInjector, ListActivityInjector, ItemListFragmentInjector, ItemDetailFragmentInjector, ShareFragmentInjector, AccountActivityInjector, FriendsFragmentInjector, SettingsActivityInjector,
135. ⚒ abstract class AppScope
136. ⚒ abstract class AppObjectGraph
137. ⚒ abstract class AppObjectGraph interface MyFragmentInjector { fun inject(instance: MyFragment) }
138. ⚒ abstract class AppObjectGraph interface MyFragmentInjector { fun inject(instance: MyFragment) } @ContributesTo(AppObjectGraph :: class)
139. ⚒ abstract class AppObjectGraph interface MyFragmentInjector { fun inject(instance: MyFragment) } @ContributesTo(AppObjectGraph : @Module class CrashModule { @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { }
140. ⚒ abstract class AppObjectGraph interface MyFragmentInjector { fun inject(instance: MyFragment) } @ContributesTo(AppObjectGraph : @Module class CrashModule { @Provides } fun provideBackend(token: ApiToken) Backend return Backend(token) : { } @ContributesTo(AppObjectGraph :: class)
141. @Component(modules = [ CrashModule :: class ]) interface AppComponent , AnalyticsModule :: class, NetworkModule : : class BillingModule : : class DatabaseModule :: class FileModule :: class UserModule :: class , , , , , ⚒ : MyFragmentInjector, ListActivityInjector, ItemListFragmentInjector, ItemDetailFragmentInjector, ShareFragmentInjector, AccountActivityInjector, FriendsFragmentInjector, SettingsActivityInjector, @MergeComponent(scope = AppObjectGraph :
142. interface AppComponent ⚒ @MergeComponent(scope = AppObjectGraph :: class)
143. ⚒ class RealCrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ): CrashReporter { // . .. }
144. ⚒ @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 { // . .. }
145. ⚒ class RealCrashReporter @Inject constructor( private val userProp: Property, private val backend: Backend, ): CrashReporter { } @ContributesBinding(AppObjectGraph :: class)
146. ⚒ Anvil Dagger 🗡 +
147. 🗡 Demystifying Dagger Ryan Harter @ryan@harter.us