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Dagger + Anvil
Learning to Love Dependency Injection
Ralf Wondratschek
@vRallev
Gabriel Peal
@gpeal8
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Dagger 2 Refresher - Basic
@Singleton
@Component
interface AppComponent
class MainApplication : Application() {
lateinit var component : AppComponent
override fun onCreate () {
super.onCreate()
component = DaggerAppComponent.create()
}
}
:app
@Singleton
class WeatherRepository @Inject constructor() {
suspend fun getForecast(): List = TODO()
}
:feature.weather
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Dagger 2 Refresher - Interface + Impl
@Singleton
@Component(modules = [WeatherModule::class])
interface AppComponent
interface WeatherRepository {
suspend fun getForecast(): List
}
:lib.weather
@Singleton
class WeatherRepositoryImpl @Inject constructor () : WeatherRepository {
override suspend fun getForecast (): List = TODO()
}
@Module
abstract class WeatherModule {
@Binds
abstract fun bindsWeatherRepository (r: WeatherRepositoryImpl ): WeatherRepository
}
:app
:feature.weather
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Dagger 2 Refresher - Binding Interface
@Singleton
@Component
interface AppComponent : WeatherBindings
interface WeatherBindings {
fun inject(fragment: WeatherFragment)
fun weatherRepository(): WeatherRepository
}
:app
:feature.weather
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Dagger 2 Refresher - Multibindings
@Singleton
@Component
interface AppComponent
:app
interface WeatherDataSource {
suspend fun getForecast
(): List
}
class WeatherChannelDataSource @Inject constructor
() : WeatherDataSource {
override suspend fun getForecast
(): List = TODO()
}
class WeatherUndergroundDataSource @Inject constructor
(): WeatherDataSource {
override suspend fun getForecast
(): List = TODO()
}
@Singleton
class WeatherRepository @Inject constructor
(
private val userPrefs: UserPrefs,
private val dataSources
: Map,
) {
suspend fun getForecast
(): List = TODO()
}
@Module
abstract class WeatherModule {
@Binds
@IntoMap
@StringKey ("WeatherChannel" )
abstract fun bindsWeatherChannel (s: WeatherChannelDataSource ): WeatherDataSource
@Binds
@IntoMap
@StringKey ("WeatherUnderground" )
abstract fun bindsWeatherUnderground (s: WeatherUndergroundDataSource ): WeatherDataSource
}
:feature.weather
(modules = [WeatherModule::class])
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Dagger 2
● Why it’s good
○ Build time guarantee
○ Fast at runtime (no reflection)
○ Huge community (Stack Overflow/Blog posts galore)
○ You can get it to do just about anything if you need it
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Dagger 2
● Why it’s not so good
○ Boilerplate
○ Complicated to learn (names aren’t great)
○ Build time (kapt)
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Why Anvil?
● Opinionated module structure
● Hundreds of demo applications
→ Boilerplate code became a problem
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Why Anvil?
:app.1
@Component(
WeatherModule, LocationModule
)
AppComponent
:app.2
@Component(
LocationModule, UserModule
)
AppComponent
:app.3
@Component(
LocationModule, UserModule
)
AppComponent
:feature.1
WeatherModule
:feature.2
LocationModule
:feature.3
UserModule
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Why Anvil?
Try to build :demo app
Add missing dependencies
in build.gradle file
Sync :demo module in
Android Studio
Add Dagger modules to
Dagger components
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Why Anvil?
Try to build :demo app
Add missing dependencies
in build.gradle file
Sync :demo module in
Android Studio
Add Dagger modules to
Dagger components
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Why Anvil?
@Singleton
@Component(modules = [WeatherModule::class])
interface AppComponent
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Why Anvil?
@Singleton
@Component(modules = [WeatherModule::class])
interface AppComponent
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Why Anvil?
● A Dagger module must know to which component it belongs
● A Dagger component must know which modules it needs to
include
→ The scope is the shared connection
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Why Anvil?
@Component(modules = [WeatherModule::class])
interface AppComponent
@Module
object WeatherModule
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Why Anvil?
@MergeComponent(AppScope::class)
interface AppComponent
@Module
@ContributesTo(AppScope::class)
object WeatherModule
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Why Anvil?
@MergeComponent(AppScope::class)
interface AppComponent
@Module
@ContributesTo(AppScope::class)
object WeatherModule
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Why Anvil?
:app.1
@Component(
WeatherModule, LocationModule
)
AppComponent
:app.2
@Component(
LocationModule, UserModule
)
AppComponent
:app.3
@Component(
LocationModule, UserModule
)
AppComponent
:feature.1
WeatherModule
:feature.2
LocationModule
:feature.3
UserModule
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Why Anvil?
:app.1
@MergeComponent(AppScope)
AppComponent
:app.2
@MergeComponent(AppScope)
AppComponent
:app.3
@MergeComponent(AppScope)
AppComponent
:feature.1
@ContributesTo(AppScope)
WeatherModule
:feature.2
@ContributesTo(AppScope)
LocationModule
:feature.3
@ContributesTo(AppScope)
UserModule
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Why Anvil?
:app.1
@MergeComponent(AppScope)
AppComponent
:app.2
@MergeComponent(AppScope)
AppComponent
:app.3
@MergeComponent(AppScope)
AppComponent
:feature.1
@ContributesTo(AppScope)
WeatherModule
:feature.2
@ContributesTo(AppScope)
LocationModule
:feature.3
@ContributesTo(AppScope)
UserModule
:core
object AppScope
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Why Anvil?
● Allows you to construct the dependency graph in a loose
way
● Aligns the build graph with the dependency graph
● Moves decision which scope to use to the declaration side
● Allows you to add new Dagger modules easily to all apps
● Creating new applications is faster
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Dagger 2 - Basic
@Singleton
@Component
interface AppComponent
class MainApplication : Application() {
lateinit var component : AppComponent
override fun onCreate () {
super.onCreate()
component = DaggerAppComponent.create()
}
}
:app
@Singleton
class WeatherRepository @Inject constructor() {
suspend fun getForecast(): List = TODO()
}
:feature.weather
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Anvil - Basic
@Singleton
@MergeComponent(AppScope::class)
interface AppComponent
class MainApplication : Application() {
lateinit var component : AppComponent
override fun onCreate () {
super.onCreate()
component = DaggerAppComponent.create()
}
}
@Singleton
class WeatherRepository @Inject constructor() {
suspend fun getForecast(): List = TODO()
}
interface AppScope
:app
:feature.weather
:lib.scopes
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Anvil - Basic
@Singleton
@MergeComponent(AppScope::class)
interface AppComponent
Two different names to memorize
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Anvil - Basic
@SingleIn(AppScope::class)
@MergeComponent(AppScope::class)
interface AppComponent
Two different names to memorize
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Anvil - Basic
@Singleton
@MergeComponent(AppScope::class)
interface AppComponent
class MainApplication : Application() {
lateinit var component: AppComponent
override fun onCreate() {
super.onCreate()
component = DaggerAppComponent.create()
}
}
@Singleton
class WeatherRepository @Inject constructor() {
suspend fun getForecast(): List = TODO()
}
interface AppScope
:app
:feature.weather
:lib.scopes
@Scope
@Retention(AnnotationRetention.RUNTIME)
annotation class SingleIn(val clazz: KClass<*>)
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Anvil - Basic
@SingleIn(AppScope::class)
@MergeComponent(AppScope::class)
interface AppComponent
class MainApplication : Application() {
lateinit var component: AppComponent
override fun onCreate() {
super.onCreate()
component = DaggerAppComponent.create()
}
}
@SingleIn(AppScope::class)
class WeatherRepository @Inject constructor() {
suspend fun getForecast(): List = TODO()
}
interface AppScope
:app
:feature.weather
:lib.scopes
@Scope
@Retention(AnnotationRetention.RUNTIME)
annotation class SingleIn(val clazz: KClass<*>)
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Dagger 2 - Interface + Impl
@Singleton
@Component(modules = [WeatherModule::class])
interface AppComponent
interface WeatherRepository {
suspend fun getForecast(): List
}
:lib.weather
@Singleton
class WeatherRepositoryImpl @Inject constructor () : WeatherRepository {
override suspend fun getForecast (): List = TODO()
}
@Module
abstract class WeatherModule {
@Binds
abstract fun bindsWeatherRepository (r: WeatherRepositoryImpl ): WeatherRepository
}
:app
:feature.weather
BOILERPLATE 🔥
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Anvil - Interface + Impl
@SingleIn(AppScope::class)
@ContributesBinding(AppScope::class)
class WeatherRepositoryImpl @Inject constructor() : WeatherRepository
{
override suspend fun getForecast(): List = TODO()
}
:lib.weather
:feature.weather
interface WeatherRepository {
suspend fun getForecast(): List
}
@Singleton
@MergeComponent(AppScope::class)
interface AppComponent
:app
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Dagger 2 - Binding Interface
@Singleton
@Component
interface AppComponent : WeatherBindings
interface WeatherBindings {
fun inject(fragment: WeatherFragment)
fun weatherRepository(): WeatherRepository
}
:app
:feature.weather
BOILERPLATE 🔥
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Anvil - Binding Interface
@ContributesTo(AppScope::class)
interface WeatherBindings {
fun inject(fragment: WeatherFragment)
fun weatherRepository(): WeatherRepository
}
:feature.weather
@Singleton
@MergeComponent(AppScope::class)
interface AppComponent
:app
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Dagger 2 - Multibindings
@Singleton
@Component(modules = [WeatherModule::class])
interface AppComponent
interface WeatherDataSource {
suspend fun getForecast
(): List
}
class WeatherChannelDataSource @Inject constructor
() : WeatherDataSource {
override suspend fun getForecast
(): List = TODO()
}
class WeatherUndergroundDataSource @Inject constructor
(): WeatherDataSource {
override suspend fun getForecast
(): List = TODO()
}
@Singleton
class WeatherRepository @Inject constructor
(
private val userPrefs: UserPrefs,
private val dataSources
: Map,
) {
suspend fun getForecast
(): List = TODO()
}
@Module
abstract class WeatherModule {
@Binds
@IntoMap
@StringKey ("WeatherChannel" )
abstract fun bindsWeatherChannel (s: WeatherChannelDataSource ): WeatherDataSource
@Binds
@IntoMap
@StringKey ("WeatherUnderground" )
abstract fun bindsWeatherUnderground (s: WeatherUndergroundDataSource ): WeatherDataSource
}
:app
:feature.weather
BOILERPLATE 🔥
BOILERPLATE 🔥
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Anvil - Multibindings
@Singleton
@MergeComponent(AppScope::class)
interface AppComponent
:app
:feature.weather
interface WeatherDataSource {
suspend fun getForecast(): List
}
@StringKey("WeatherChannel")
@ContributesMultibinding(AppScope::class)
class WeatherChannelDataSource @Inject constructor() :
WeatherDataSource {
override suspend fun getForecast(): List =
TODO()
}
@StringKey("WeatherUnderground")
@ContributesMultibinding(AppScope::class)
class WeatherUndergroundDataSource @Inject constructor():
WeatherDataSource {
override suspend fun getForecast(): List =
TODO()
}
@Singleton
class WeatherRepository @Inject constructor(
private val userPrefs: UserPrefs,
private val dataSources: Map,
) {
suspend fun getForecast(): List =
TODO()
}
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/* :app /src/main */
@SingleIn(AppScope::class)
@MergeComponent(AppScope::class)
interface AppComponent
open class MainApplication : Application() {
lateinit var daggerComponent: Any
override fun onCreate() {
super.onCreate()
daggerComponent = DaggerAppComponent.create()
}
}
Anvil - Replace dependencies in tests
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/* :app /src/androidTest */
@SingleIn(AppScope::class)
@MergeComponent(AppScope::class)
interface TestAppComponent
class TestApplication : MainApplication() {
override lateinit var daggerComponent: Any
override fun onCreate() {
super.onCreate()
daggerComponent = DaggerTestAppComponent.create()
}
}
Anvil - Replace dependencies in tests
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/* :lib.weatherdata /src/main */
interface WeatherRepository {
suspend fun getForecast(): List
}
/* :features.weatherdata /src/main */
@SingleIn(WeatherScope::class)
@ContributesBinding(WeatherScope::class)
class WeatherRepositoryImpl @Inject constructor() : WeatherRepository
Anvil - Replace dependencies in tests
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/* :lib.weatherdata /src/main */
interface WeatherRepository {
suspend fun getForecast(): List
}
/* :app /src/androidTest */
@ContributesBinding(
scope = WeatherScope::class
)
object FakeWeatherRepository : WeatherRepository {
override suspend fun getForecast(): List = listOf(1, 2, 3, 4, 5)
}
Anvil - Replace dependencies in tests
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/* :lib.weatherdata /src/main */
interface WeatherRepository {
suspend fun getForecast(): List
}
/* :app /src/androidTest */
@ContributesBinding(
scope = WeatherScope::class,
replaces = [WeatherRepositoryImpl::class]
)
object FakeWeatherRepository : WeatherRepository {
override suspend fun getForecast(): List = listOf(1, 2, 3, 4, 5)
}
Anvil - Replace dependencies in tests
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/* :lib.weatherdata /src/main */
interface WeatherRepository {
suspend fun getForecast(): List
}
/* :app /src/androidTest */
@ContributesBinding(
scope = WeatherScope::class,
replaces = [WeatherRepositoryImpl::class]
)
object FakeWeatherRepository : WeatherRepository {
override suspend fun getForecast(): List = listOf(1, 2, 3, 4, 5)
}
Anvil - Replace dependencies in tests
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What about Hilt?
● Multi-login
● Guarantee no user information leaks
across accounts
● Null safe access to account
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What about Hilt?
class WorkoutFragment : Fragment( R.layout.workout_fragment), DaggerComponentOwner {
// github/gpeal/Anvil-Sample
override val daggerComponent : WeatherComponent by fragmentComponent { scope, app ->
app.bindings().workoutComponentBuilder().create(scope)
}
}
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What about Hilt?
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What about Hilt?
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Anvil - Build Time
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Anvil - Dagger Factory Generation
plugins {
id 'org.jetbrains.kotlin.kapt'
id 'com.squareup.anvil'
}
dependencies {
api "com.google.dagger:dagger:$daggerVersion"
kapt "com.google.dagger:dagger-compiler:$daggerVersion"
}
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Anvil - Dagger Factory Generation
plugins {
id 'com.squareup.anvil'
}
anvil {
generateDaggerFactories = true
}
dependencies {
api "com.google.dagger:dagger:$daggerVersion"
}
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Build time for single modules improved by up to 65%
Anvil - Dagger Factory Generation
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Build time for our full project improved by 16% on average
Anvil - Build time
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Build time for Slack improved by 25%
Anvil - Build time
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TL;DR
● If you use Dagger already, then Anvil will make your build
times significantly faster and provide more features on top
○ (For Dagger + Hilt the diff is even bigger)
Anvil - Build time
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Extend Anvil - Custom Code Generator
interface WeatherApi {
@GET("…")
suspend fun getForecast(): Forecast
}
@Module
@ContributesTo(AppScope::class)
object WeatherApiModule {
@Provides
@Reusable
fun providesWeatherApi(retrofit: Retrofit): WeatherApi {
return retrofit.create()
}
}
@ContributesApi(AppScope::class)
Eliminated
// github/gpeal/Avil-Sample
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@Module
@ContributesTo(AppScope::class)
public abstract class WeatherViewModelModule {
@Binds
@IntoMap
@ViewModelKey(WeatherViewModel::class)
public abstract fun bindWeatherViewModelFactory(
factory: WeatherViewModel.Factory,
): TonalViewModelFactory<*, *>
}
Extend Anvil - Custom Code Generator
@ContributesViewModel(UserScope::class)
class WeatherViewModel @AssistedInject constructor(
@Assisted initialState: WeatherState,
weatherRepository: WeatherRepository,
) : MavericksViewModel(initialState) {
…
}
Eliminated
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Extend Anvil - Custom Code Generator
@ContributesFeatureFlag
enum class MyFeatureFlag(
override val flag: String,
) : BaseFeatureFlag {
MyFlag("my-flag"),
MyFlag2("my-flag-2"),
}
@Module
@ContributesTo(AppScope::class)
public abstract class MyFeatureFlagModule {
@Provides
@ElementsIntoSet
fun providesMyFeatureFlags(): Set = MyFeatureFlag.values().toSet()
}
Eliminated
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Extend Anvil - Custom Code Generator
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Thank you!
Ralf Wondratschek
@vRallev
Gabriel Peal
@gpeal8
github.com/gpeal/Anvil-Sample
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Resources
● https://github.com/square/anvil
● https://github.com/gpeal/Anvil-Sample
● https://gpeal.medium.com/dagger-anvil-learning-to-love-d
ependency-injection-on-android-8fad3d5530c9