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@Inject Basics
Jitin Sharma
@_jitinsharma
stages of dependency injection programming
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Dependency Injection
Dagger
Koin
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Why Dependency Injection
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Why Dependency Injection
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All opinions expressed in this talk are fictional in nature
and have no relation to any twitter account.
Disclaimer
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No content
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Dependency injection is a technique whereby
one object supplies the dependencies of another object
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Setter Injection
class Jitin {
lateinit var stage: Stage
fun setStage(stage: Stage) {
this.stage = stage
}
!!...
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Constructor Injection
class Jitin(private val stage: Stage) { !!...
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Constructor Injection
class Jitin(private val stage: Stage,
private var mic: Boolean = true)
Jitin(stage = getStage(), mic = false)
Jitin(stage = getStage())
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Android Components
- Activity
- Application
- Services
- !!...
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INVERSIOИ
OF CONTROL
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DogActivity
DogPresenter
DogAPI
DogRepository
DogView
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DogActivity
DogPresenter
DogAPI
DogRepository
DogView
Dependencies
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DogActivity
DogPresenter
DogAPI
DogRepository
DogView
Dependencies
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Dependency Container
val dogApi: DogApi get() = ApiClient.dogClient.create(DogApi!::class.java)
val dogRepository get() = DogRepository()
val presenter get() = DogPresenter()
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object DogDependencyContainer {
var dogView: DogView? = null
fun init(dogView: DogView) {
this.dogView = dogView
}
!!...
val dogApi: DogApi get() = ApiClient.dogClient.create(DogApi!::class.java)
val dogRepository get() = DogRepository()
val presenter get() = DogPresenter()
Dependency Container
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Dependency Container
inline fun inject(): T {
return when (T!::class) {
DogApi!::class !-> dogApi as T
DogPresenter!::class !-> presenter as T
DogRepository!::class !-> dogRepository as T
DogView!::class !-> dogView as T
else !-> throw DependencyNotFoundException()
}
}
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Dependency Container
class DogPresenter {
private val dogView by lazy { inject() }
private val dogRepository by lazy { inject() }
class DogRepository {
private val dogApi by lazy { inject() }
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Dependency Container
class DogActivity : AppCompatActivity(), DogView {
private val dogPresenter by lazy { inject() }
!!...
override fun onCreate(savedInstanceState: Bundle?) {
!!...
DogDependencyContainer.init(this)
!!...
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SERVICE LOCATOR
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DogActivity
DogPresenter
DogAPI
DogRepository
DogView
DependencyContainer
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DogActivity
DogPresenter
DogAPI
DogRepository
DogView
class DogRepository(private val dogApi: DogApi)
class DogPresenter(private var dogView: DogView?,
private val dogRepository: DogRepository)
!// Interface
DependencyContainer
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Dependency Container
private val dogApi get() = ApiClient.dogClient.create(DogApi!::class.java)
private val dogRepository get() = DogRepository(dogApi)
val presenter get() = DogPresenter(dogView, dogRepository)
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Dependency Container
class DogActivity : AppCompatActivity(), DogView {
private val dogPresenter by lazy { inject() }
!!...
override fun onCreate(savedInstanceState: Bundle?) {
!!...
DogDependencyContainer.init(this)
!!...
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dagger
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@Inject javax.inject (JSR 330)
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@Inject javax.inject (JSR 330)
@Provides
@Provides
!!...
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@Inject javax.inject (JSR 330)
@Provides
@Provides
!!...
@Module
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@Inject javax.inject (JSR 330)
@Provides
@Provides
!!...
@Module @Component
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DogActivity
DogPresenter
DogAPI
DogRepository
DogView
@Provides
fun dogView(): DogView = dogView
@Provides
fun dogApi(): DogApi = ApiClient.dogClient.create(DogApi!::class.java)
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class DogRepository @Inject constructor(private val dogApi: DogApi)
class DogPresenter @Inject constructor(
private var dogView: DogView?,
private val dogRepository: DogRepository
)
Injecting Constructors
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@Component(modules = [DogModule!::class])
interface DogComponent {
fun inject(mainActivity: MainActivity)
}
Wiring up dependencies
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Injecting Dependencies
class MainActivity : AppCompatActivity(), DogView {
@Inject
lateinit var dogPresenter: DogPresenter
override fun onCreate(savedInstanceState: Bundle?) {
DaggerDogComponent.builder().dogModule(DogModule((this))).build().inject(this)
}
}
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public final class DaggerDogComponent implements DogComponent {
private DogRepository getDogRepository() {
return new DogRepository(DogModule_DogApiFactory.dogApi(dogModule));
}
private DogPresenter getDogPresenter() {
return new DogPresenter(DogModule_DogViewFactory.dogView(dogModule), getDogRepository());
}
!!...
Component Generation
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Injection via code generation
DaggerDogComponent!!... !..inject(this) DogActivity
DogActivity.kt
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Injection via code generation
DaggerDogComponent!!... !..inject(this) DogActivity
@Override
public void inject(DogActivity dogActivity) {
injectDogActivity(dogActivity);
}
DogActivity.kt
DaggerDogComponent.java
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Injection via code generation
DaggerDogComponent!!... !..inject(this) DogActivity
@Override
public void inject(DogActivity dogActivity) {
injectDogActivity(dogActivity);
}
public static void injectDogPresenter(DogActivity instance,
DogPresenter dogPresenter) {
instance.dogPresenter = dogPresenter;
}
DogActivity.kt
DaggerDogComponent.java
DogActivity_MembersInjector.java
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Injection via code generation
DaggerDogComponent!!... !..inject(this) DogActivity
@Override
public void inject(DogActivity dogActivity) {
injectDogActivity(dogActivity);
}
public static void injectDogPresenter(DogActivity instance,
DogPresenter dogPresenter) {
instance.dogPresenter = dogPresenter;
}
@Inject
lateinit var dogPresenter: DogPresenter
DogActivity.kt
DaggerDogComponent.java
DogActivity_MembersInjector.java
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Scopes
@Singleton
@Component(modules = [AppModule!::class])
interface AppComponent {
!!...
@DogScope
@Component(modules = [DogModule!::class], dependencies = [AppComponent!::class])
interface DogComponent {
!!...
DogComponent.kt
AppComponent.kt
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DaggerDogComponent.builder()
.appComponent(appComponent)
.dogModule(DogModule((this)))
.build()
.inject(this)
Inversion of Control
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dagger.android
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AndroidInjector
Activity Fragment
Service BrodcastReceiver ContentProvider
Core Components
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@Module
class DogModule {
@Provides
fun providesDogView(dogActivity: DogActivity): DogView = dogActivity
!!...
@Binds
abstract fun provideDogView(dogActivity: DogActivity): DogView
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@Module
abstract class BuildersModule {
@ContributesAndroidInjector(modules = [DogModule!::class])
abstract fun bindDogActivity(): DogActivity
!!...
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@Singleton
@Component(modules = [AndroidInjectionModule!::class, AppModule!::class, BuildersModule!::class])
interface AppComponent {
@Component.Builder
interface Builder {
@BindsInstance
fun application(application: AnimalApp): Builder
fun build(): AppComponent
}
fun inject(app: AnimalApp)
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class DogActivity : AppCompatActivity(), DogView {
@Inject
lateinit var dogPresenter: DogPresenter
!!...
override fun onCreate(savedInstanceState: Bundle?) {
AndroidInjection.inject(this)
!!...
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AndroidInjection.inject(this)
Activity
Fragment
Service
Content Provider
Broadcast Receiver
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Application
Activity Fragment Service Content Provider Broadcast Receiver
HasAndroidInjector
HasAndroidInjector
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Application
Activity Fragment Service Content Provider Broadcast Receiver
HasAndroidInjector
HasAndroidInjector
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class AnimalApp : Application(), HasAndroidInjector {
@Inject
lateinit var dispatchingAndroidInjector: DispatchingAndroidInjector
override fun androidInjector(): AndroidInjector = dispatchingAndroidInjector
override fun onCreate() {
super.onCreate()
DaggerAppComponent.builder()
.application(this)
.build()
.inject(this)
!!...
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class AnimalApp : Application(), HasAndroidInjector {
@Inject
lateinit var dispatchingAndroidInjector: DispatchingAndroidInjector
override fun androidInjector(): AndroidInjector = dispatchingAndroidInjector
override fun onCreate() {
super.onCreate()
DaggerAppComponent.builder()
.application(this)
.build()
.inject(this)
!!...
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class AnimalApp : Application(), HasAndroidInjector {
@Inject
lateinit var dispatchingAndroidInjector: DispatchingAndroidInjector
override fun androidInjector(): AndroidInjector = dispatchingAndroidInjector
override fun onCreate() {
super.onCreate()
DaggerAppComponent.builder()
.application(this)
.build()
.inject(this)
!!...
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AppComponent
Activity Modules
Builder Module
(@ContributesAndroidInjector)
//Generated
DaggerAppComponent
SubComponent: AndroidInjector<>
Provider
Map
DispatchingAndroidInjector
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//Generated
DaggerAppComponent
SubComponent: AndroidInjector<>
Provider
Map
DispatchingAndroidInjector
@Inject
dispatchingAndroidInjector: DispatchingAndroidInjector
Application class
Activity Class
AndroidInjection.inject(this)
@Override
public void inject(DogActivity arg0) {
injectDogActivity(arg0);
}
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class DogActivity : DaggerAppCompatActivity(), DogView {
@Inject
lateinit var dogPresenter: DogPresenter
!!...
Support Module
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KOTLIN
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Kotlin
Delegation Lambda DSL
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KOIN
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• A Dependency Injection Framework for Kotlin
• Does not use code generation
• Works using Lambdas and Extensions
KOIN
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val catModule = module {
single { ApiClient.catClient.create(CatApi!::class.java) }
single { CatRepository(get()) }
factory { (catView: CatView) !-> CatPresenter(catView, get()) }
}
Module Declaration
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val catModule = module {
single { ApiClient.catClient.create(CatApi!::class.java) }
single { CatRepository(get()) }
factory { (catView: CatView) !-> CatPresenter(catView, get()) }
}
Module Declaration
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Startup Configuration
class AnimalApp : Application(){
override fun onCreate() {
super.onCreate()
startKoin {
androidContext(this@AnimalApp)
modules(listOf(catModule, dogModule, appModule))
}
!!...
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class CatActivity : AppCompatActivity(), CatView {
private val catPresenter: CatPresenter by inject { parametersOf(this) }
private val imageLoader: ImageLoader by inject()
!!...
Injecting Members
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Load
Modules
BeanRegistry
HashSet
by inject()
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Load
Modules
BeanRegistry
HashSet
by inject()
Service Locator
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Modules and Scopes
unloadKoinModules(catModule)
loadKoinModules(catModule)
!// GlobalScope
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Modules and Scopes
scope(named()) {
scoped { (catView: CatView) !-> CatPresenter(catView, get()) }
}
CatPresenter by currentScope.inject { !!...
LifeCycleOwner
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Modules and Scopes
scope(named()) {
scoped { (catView: CatView) !-> CatPresenter(catView, get()) }
}
CatPresenter by currentScope.inject { !!...
LifeCycleOwner
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Koin has
• Easy configuration
• Drop in support for Android with ViewModels and Scopes
• Excellent documentation and testing support
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Koin does not have
• Strict Compile time safety
• Facility of automatic constructors without using reflection
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Probably Yes
Do you need Dependency Injection
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It Depends
Do you need DI frameworks?
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Service Locator?
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HATERS GONNA HATE
SERVICE LOCATORS GONNA LOCATE
- 10x Engineer
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USE WHAT WORKS FOR YOU
- 1x Engineer
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Thank You
@_jitinsharma
jitinsharma.in