Dagger 2 Android: Defeat the Dahaka

Presentation for Chicago Roboto 2018.

Github Demo : https://github.com/ragdroid/Dahaka
Medium Blogs : https://proandroiddev.com/dagger-2-android-defeat-the-dahaka-b1c542233efc

Transcript

1. Garima Jain
   @ragdroid
   “Defeat the Dahaka"
   Dagger 2 Android
   Version: @chicagoroboto
   

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2. @ragdroid
   #chicagoroboto
   POP QUIZ
   • Dagger2?
   • Dagger Android
   • Prince of Persia
   

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3. ABOUT THE TALK
   

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4. Theme: Prince of Persia
   • Prince uses Dagger
   • Dagger can reverse time
   • Dahaka, (guardian of timeline)
   • Dahaka comes to kill the Prince.
   

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5. Analogy
   • Prince = Us
   • Dagger = Dagger
   • Dahaka (Enemy) = Generated Code, Complexity
   

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6. Analogy
   • Developer uses Dagger
   • Developer starts backtracking the generated code
   • Developer is chased by the Dahaka (complexity of generated code)
   

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7. Agenda
   • Scopes - “Face of the Dahaka”
   • @Singleton Scopes
   • @Reusable Scopes
   • Custom Scopes
   • Component Dependencies - “Unleash the Beast”
   • Dependent Component
   • Subcomponent
   • Dagger Android - “Befriend the Beast”
   

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8. Who?
   Assumption : Basic familiarity with Dagger
   

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9. SCOPES
   “FACE OF THE DAHAKA”
   

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10. Scope
    How long a scoped instance lives
    (javax.inject)
    

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11. @Singleton
    Scope of dependency is throughout the application
    (javax.inject)
    

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12. @ragdroid
    #chicagoroboto
    @SINGLETON
    EXAMPLE
    

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13. AppComponent
    @Component(modules = [AppModule::class])
    @Singleton
    interface AppComponent {
    fun application(): Application
    }
    

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14. AppComponent
    @Component(modules = [AppModule::class])
    @Singleton
    interface AppComponent {
    fun application(): Application
    }
    

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15. @ragdroid
    #chicagoroboto
    CASE 1
    DEPENDENCY WITH SCOPE
    

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16. AppModule
    @Module
    class AppModule(val application: Application) {
    @Provides
    @Singleton
    fun provideApplication(): Application = application
    }
    

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17. AppModule
    @Module
    class AppModule(val application: Application) {
    @Provides
    @Singleton
    fun provideApplication(): Application = application
    }
    

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18. DaggerAppComponent
    @Generated
    public final class DaggerAppComponent implements AppComponent {
    private Provider applicationProvider;
    /** other code **/
    private void initialize(final Builder builder) {
    this.applicationProvider =
    DoubleCheck.provider(
    AppModule_ApplicationFactory.create(builder.appModule));
    }
    }
    (Generated)
    

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19. Provider
    DaggerAppComponent
    @Generated
    public final class DaggerAppComponent implements AppComponent {
    private Provider applicationProvider;
    /** other code **/
    private void initialize(final Builder builder) {
    this.applicationProvider =
    DoubleCheck.provider(
    AppModule_ApplicationFactory.create(builder.appModule));
    }
    }
    (Generated)
    

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20. Provider
    • For each @Provides annotation dagger generates a Provider *
    • Dagger’s Factory interface is also a Provider
    • Dagger has various implementations of Providers:
    • SingleCheck
    • DoubleCheck
    (javax.inject)
    * Not for unscoped dependencies - Coming up
    

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21. DaggerAppComponent
    @Generated
    public final class DaggerAppComponent implements AppComponent {
    private Provider applicationProvider;
    /** other code **/
    private void initialize(final Builder builder) {
    this.applicationProvider =
    DoubleCheck.provider(
    AppModule_ApplicationFactory.create(builder.appModule));
    }
    }
    (Generated)
    

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22. DaggerAppComponent
    @Generated
    public final class DaggerAppComponent implements AppComponent {
    private Provider applicationProvider;
    /** other code **/
    private void initialize(final Builder builder) {
    this.applicationProvider =
    DoubleCheck.provider(
    AppModule_ApplicationFactory.create(builder.appModule));
    }
    }
    (Generated)
    

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23. DaggerAppComponent
    @Generated
    public final class DaggerAppComponent implements AppComponent {
    private Provider applicationProvider;
    /** other code **/
    private void initialize(final Builder builder) {
    this.applicationProvider =
    DoubleCheck.provider(
    AppModule_ApplicationFactory.create(builder.appModule));
    }
    }
    (Generated)
    

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24. DaggerAppComponent
    @Generated
    public final class DaggerAppComponent implements AppComponent {
    private Provider applicationProvider;
    /** other code **/
    private void initialize(final Builder builder) {
    this.applicationProvider =
    DoubleCheck.provider(
    AppModule_ApplicationFactory.create(builder.appModule));
    }
    }
    (Generated)
    

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25. DoubleCheck
    Memoizes value using Double-Check idiom.
    (dagger.internal)
    

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26. DoubleCheck
    Memoizes value using Double-Check idiom.
    public T get() {

    Object result = instance;

    if (result == UNINITIALIZED) {

    synchronized (this) {

    result = instance;

    if (result == UNINITIALIZED) {

    result = provider.get();

    

    Object currentInstance = instance;
    // other code

    instance = result;

    

    provider = null;

    }

    }

    }

    return (T) result;

    }
    (dagger.internal)
    

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27. DoubleCheck
    Memoizes value using Double-Check idiom.
    public T get() {

    Object result = instance;

    if (result == UNINITIALIZED) {

    synchronized (this) {

    result = instance;

    if (result == UNINITIALIZED) {

    result = provider.get();

    

    Object currentInstance = instance;
    // other code

    instance = result;

    

    provider = null;

    }

    }

    }

    return (T) result;

    }
    (dagger.internal)
    

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28. DoubleCheck
    Memoizes value using Double-Check idiom.
    public T get() {

    Object result = instance;

    if (result == UNINITIALIZED) {

    synchronized (this) {

    result = instance;

    if (result == UNINITIALIZED) {

    result = provider.get();

    

    Object currentInstance = instance;
    // other code

    instance = result;

    

    provider = null;

    }

    }

    }

    return (T) result;

    }
    (dagger.internal)
    

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29. @ragdroid
    #chicagoroboto
    CASE 2
    DEPENDENCY W/O SCOPE
    

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30. AppModule
    @Module
    class AppModule(val application: Application) {
    @Provides //No @Singleton annotation
    fun provideApplication(): Application = application
    }
    

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31. AppModule
    @Module
    class AppModule(val application: Application) {
    @Provides //No @Singleton annotation
    fun provideApplication(): Application = application
    }
    

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32. DaggerAppComponent
    @Generated
    public final class DaggerAppComponent implements AppComponent {
    private Provider applicationProvider;
    /** other code **/
    private void initialize(final Builder builder) {
    this.applicationProvider =
    ApplicationFactory.create(builder.appModule);
    }
    }
    (Generated)
    

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33. DaggerAppComponent
    @Generated
    public final class DaggerAppComponent implements AppComponent {
    private Provider applicationProvider;
    /** other code **/
    private void initialize(final Builder builder) {
    this.applicationProvider =
    ApplicationFactory.create(builder.appModule);
    }
    }
    (Generated)
    

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34. DaggerAppComponent
    @Generated
    public final class DaggerAppComponent implements AppComponent {
    private Provider applicationProvider;
    /** other code **/
    private void initialize(final Builder builder) {
    this.applicationProvider =
    ApplicationFactory.create(builder.appModule);
    }
    }
    (Generated)
    

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35. DaggerAppComponent
    public final class DaggerAppComponent implements AppComponent {
    private AppModule appModule;
    @Override
    public Application application() {
    //No Factory Instance Creation
    return ApplicationFactory.proxyProviderApplication(appModule);
    }
    }
    (Generated)
    Since dagger 2.12
    

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36. DaggerAppComponent
    public final class DaggerAppComponent implements AppComponent {
    private AppModule appModule;
    @Override
    public Application application() {
    //No Factory Instance Creation
    return ApplicationFactory.proxyProviderApplication(appModule);
    }
    }
    (Generated)
    Since dagger 2.12
    

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37. DaggerAppComponent
    public final class DaggerAppComponent implements AppComponent {
    private AppModule appModule;
    @Override
    public Application application() {
    //No Factory Instance Creation
    return appModule.provideApplication();
    }
    }
    (Generated)
    Since dagger 2.12
    

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38. Take Aways
    • DONT “Scope All the Things!”
    • Scoping has overheads.
    • By-default no Scope.
    • Scope only when needed
    • Like for Heavy Objects
    

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39. @ragdroid
    #chicagoroboto
    CASE 3
    @REUSABLE
    

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40. @Reusable
    • Limit the instantiation.
    • Use when Exact same instance not needed.
    • Can Have multiple sub-components caching different instances.
    

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41. ReusableComponent
    

    @Component(modules = [ReusableModule::class])
    interface ReusableComponent {
    fun someObject(): SomeObject
    }
    

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42. ReusableComponent
    

    @Component(modules = [ReusableModule::class])
    interface ReusableComponent {
    fun someObject(): SomeObject
    }
    

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43. SomeObject
    @Reusable
    class SomeObject @Inject constructor()
    

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44. DaggerReusableComponent
    @Generated
    public final class DaggerReusableComponent implements
    ReusableComponent {
    /** other code **/
    Provider someObjectProvider;
    private void initialize(final Builder builder) {
    this.someObjectProvider =
    SingleCheck.provider(SomeObject_Factory.create());
    }
    }
    (Generated)
    

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45. DaggerReusableComponent
    @Generated
    public final class DaggerReusableComponent implements
    ReusableComponent {
    /** other code **/
    Provider someObjectProvider;
    private void initialize(final Builder builder) {
    this.someObjectProvider =
    SingleCheck.provider(SomeObject_Factory.create());
    }
    }
    (Generated)
    

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46. DaggerReusableComponent
    @Generated
    public final class DaggerReusableComponent implements
    ReusableComponent {
    /** other code **/
    Provider someObjectProvider;
    private void initialize(final Builder builder) {
    this.someObjectProvider =
    SingleCheck.provider(SomeObject_Factory.create());
    }
    }
    (Generated)
    

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47. SingleCheck
    Memoizes value using simple lazy initialization and caching
    (dagger.internal)
    

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48. Memoizes value using simple lazy initialization and caching
    public T get() {

    

    Provider providerReference = provider;

    if (instance == UNINITIALIZED) {

    instance = providerReference.get();

    provider = null;

    }

    return (T) instance;

    }
    (dagger.internal)
    SingleCheck
    

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49. Memoizes value using simple lazy initialization and caching
    public T get() {

    

    Provider providerReference = provider;

    if (instance == UNINITIALIZED) {

    instance = providerReference.get();

    provider = null;

    }

    return (T) instance;

    }
    (dagger.internal)
    SingleCheck
    

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50. @Singleton vs @Reusable vs No Scope
    • Heavy mutable object with State : @Singleton
    • Heavy immutable object / stateless : @Reusable
    • Not Heavy : No Scope
    •
    
    

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51. @ragdroid
    #chicagoroboto
    GOD APP MODULE
    

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52. @ragdroid
    #chicagoroboto
    App Module
    AppComponent
    @Module
    public class
    AppModule {
    private
    final
    Application
    application;
    @Provides
    @Si
    AppModule
    @Singleton
    @Component(modules =
    AppModule.class)
    @Singleton
    public interface
    AppComponent {
    Application
    application();
    }
    

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53. @ragdroid
    #chicagoroboto
    Big App Module
    AppComponent
    @Module
    public class AppModule {
    private final Application
    application;
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    AppModule
    @Singleton
    @Component(modules =
    AppModule.class)
    @Singleton
    public interface
    AppComponent {
    Application
    application();
    }
    

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54. @ragdroid
    #chicagoroboto
    AppComponent
    @Module
    public class AppModule {
    private final Application application;
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    }
    AppModule
    @Singleton
    Big App Module
    @Component(modules =
    AppModule.class)
    @Singleton
    public interface
    AppComponent {
    Application
    application();
    }
    

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55. @ragdroid
    #chicagoroboto
    AppComponent
    @Module
    public class AppModule {
    private final Application application;
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    }
    AppModule
    @Singleton
    God Module
    God App Module
    @Component(modules =
    AppModule.class)
    @Singleton
    public interface
    AppComponent {
    Application
    application();
    }
    

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56. @ragdroid
    #chicagoroboto
    God App Module
    How To Improve?
    
    

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57. @ragdroid
    #chicagoroboto
    God App Module
    Splitting App Module
    
    

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58. @ragdroid
    #chicagoroboto
    AppComponent
    @Module
    public class AppModule {
    private final Application application;
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    }
    @Singleton
    @Component(modules =
    AppModule.class)
    @Singleton
    public interface
    AppComponent {
    Application
    application();
    }
    Splitting App Module
    ApiModule
    AppModule
    

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59. @ragdroid
    #chicagoroboto
    Splitting App Module
    @Module
    public class AppModule {
    private final Application application;
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    }
    AppModule
    ApiModule
    AppComponent
    @Singleton
    @Component(modules =
    AppModule.class)
    @Singleton
    public interface
    AppComponent {
    Application
    application();
    }
    

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60. @ragdroid
    #chicagoroboto
    Splitting App Module
    AppComponent
    @Module
    public class AppModule {
    private final Application application;
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    @Provides
    @Singleton
    Application applicationProvider() {
    return application;
    }
    }
    AppModule
    @Singleton
    @Component(modules =
    AppModule.class)
    @Singleton
    public interface
    AppComponent {
    Application
    application();
    }
    ApiModule
    @Component(
    modules = AppModule.class,
    ApiModule.class)
    

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61. @ragdroid
    #chicagoroboto
    Splitting App Module
    
    

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62. @ragdroid
    #chicagoroboto
    How to Improve?
    • Better Scope Management
    • More modularity
    • Custom Scopes :
    • @UserScope
    • @ActivityScope
    • @FragmentScope
    

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63. @ragdroid
    #chicagoroboto
    Custom Scopes
    

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64. @ragdroid
    #chicagoroboto
    Custom Scopes
    Multiple Components
    

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65. Multiple Components
    1. Dependent Components
    2. Sub-Components
    

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66. COMPONENT
    DEPENDENCIES
    

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67. @ragdroid
    #chicagoroboto
    SUB COMPONENT
    VS
    DEPENDENT COMPONENT
    

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68. AppComponent (@Singleton)
    UserComponent
    (@UserScope)
    UserComponent
    @UserScope
    Login
    Component
    @ActivityScope
    Home
    Component
    Items
    Component
    Login
    Component
    Home
    Component
    Items
    Component
    Fragments Fragments
    Launch
    pikachu Login
    Log-Out
    jigglypuff
    Application
    

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69. AppComponent
    @Singleton
    DaggerAppComponent
    LoginComponent
    Sub Component
    @ActivityScope
    Dependent Component
    DaggerUserComponent
    • dependency
    HomeComponent
    ItemsComponent
    @UserScope
    

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70. @ragdroid
    #chicagoroboto
    APP COMPONENT
    

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71. @Singleton
    @Component(modules = arrayOf(AppModule::class, ApiModule::class))
    interface AppComponent {
    fun loginBuilder(): LoginComponent.Builder
    }
    AppComponent
    

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72. @Singleton
    @Component(modules = arrayOf(AppModule::class, ApiModule::class))
    interface AppComponent {
    fun loginBuilder(): LoginComponent.Builder
    }
    AppComponent
    

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73. @ragdroid
    #chicagoroboto
    DAHAKA
    APPLICATION
    

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74. class DahakaApplication : Application() {
    override fun onCreate() {
    super.onCreate()
    appComponent = DaggerAppComponent
    .builder()
    .application(this)
    .build()
    }
    }
    DahakaApplication
    

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75. class DahakaApplication : Application() {
    override fun onCreate() {
    super.onCreate()
    appComponent = DaggerAppComponent
    .builder()
    .application(this)
    .build()
    }
    }
    DahakaApplication
    

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76. DEPENDENT
    COMPONENTS
    

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77. @ragdroid
    #chicagoroboto
    USER
    COMPONENT
    

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78. @Component(dependencies = arrayOf(AppComponent::class),
    modules = arrayOf(UserModule::class))
    @UserScope
    interface UserComponent {
    }
    UserComponent
    

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79. @Component(dependencies = arrayOf(AppComponent::class),
    modules = arrayOf(UserModule::class))
    @UserScope
    interface UserComponent {
    }
    UserComponent
    

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80. @ragdroid
    #chicagoroboto
    USER
    MANAGER
    

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81. @Singleton
    class UserManager @Inject
    constructor(private val service: PokemonService) {
    var userComponent: UserComponent? = null
    private set
    public fun createUserSession(pokemon: Pokemon) {
    userComponent = DaggerUserComponent.builder()
    .appComponent(DahakaApplication.app.appComponent)
    .pokeMon(pokemon)
    .build()
    }
    …
    }
    UserManager
    

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82. @Singleton
    class UserManager @Inject
    constructor(private val service: PokemonService) {
    var userComponent: UserComponent? = null
    private set
    public fun createUserSession(pokemon: Pokemon) {
    userComponent = DaggerUserComponent.builder()
    .appComponent(DahakaApplication.app.appComponent)
    .pokeMon(pokemon)
    .build()
    }
    …
    }
    UserManager
    

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83. @Singleton
    class UserManager @Inject
    constructor(private val service: PokemonService) {
    var userComponent: UserComponent? = null
    private set
    public fun createUserSession(pokemon: Pokemon) {
    userComponent = DaggerUserComponent.builder()
    .appComponent(DahakaApplication.app.appComponent)
    .pokeMon(pokemon)
    .build()
    }
    …
    }
    UserManager
    

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84. @ragdroid
    #chicagoroboto
    DAGGER
    USER COMPONENT
    (Generated)
    

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85. public final class DaggerUserComponent implements UserComponent {
    …
    }
    DaggerUserComponent (Generated)
    

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86. public final class DaggerUserComponent implements UserComponent {
    …
    }
    DaggerUserComponent (Generated)
    

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87. SUB
    COMPONENTS
    

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88. @ragdroid
    #chicagoroboto
    LOGIN
    SUBCOMPONENT
    

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89. @ActivityScope
    @Subcomponent(modules = arrayOf(LoginModule::class))
    interface LoginComponent {
    ...
    }
    LoginComponent
    

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90. @ActivityScope
    @Subcomponent(modules = arrayOf(LoginModule::class))
    interface LoginComponent {
    ...
    }
    LoginComponent
    

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91. @ActivityScope
    @Subcomponent(modules = arrayOf(LoginModule::class))
    interface LoginComponent {
    ...
    }
    LoginComponent
    

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92. @ragdroid
    #chicagoroboto
    DAGGER
    APP COMPONENT
    (Generated)
    

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93. public final class DaggerAppComponent implements AppComponent {
    private final class LoginComponentImpl implements LoginComponent {
    private LoginComponentImpl(LoginComponentBuilder builder) {
    assert builder != null;
    initialize(builder);
    }
    …
    }
    }
    DaggerAppComponent(Generated)
    

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94. public final class DaggerAppComponent implements AppComponent {
    private final class LoginComponentImpl implements LoginComponent {
    private LoginComponentImpl(LoginComponentBuilder builder) {
    assert builder != null;
    initialize(builder);
    }
    …
    }
    }
    DaggerAppComponent(Generated)
    

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95. public final class DaggerAppComponent implements AppComponent {
    private final class LoginComponentImpl implements LoginComponent {
    private LoginComponentImpl(LoginComponentBuilder builder) {
    assert builder != null;
    initialize(builder);
    }
    …
    }
    }
    DaggerAppComponent(Generated)
    

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96. public final class DaggerAppComponent implements AppComponent {
    private final class LoginComponentImpl implements LoginComponent {
    private LoginComponentImpl(LoginComponentBuilder builder) {
    assert builder != null;
    initialize(builder);
    }
    …
    }
    }
    DaggerAppComponent(Generated)
    

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97. @ragdroid
    #chicagoroboto
    SUB COMPONENT
    VS
    DEPENDENT COMPONENT
    

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98. <>
    AppComponent
    fun schedulerProvider()
    @Singleton
    

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99. DaggerAppComponent
    • schedulerProvider() : @Singleton
    • userManager : @Singleton
    LoginComponentImpl
    <>
    AppComponent
    fun schedulerProvider()
    @Singleton
    @ActivityScope
    

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100. DaggerAppComponent
     • schedulerProvider() : @Singleton
     • userManager : @Singleton
     LoginComponentImpl
     <>
     AppComponent
     fun schedulerProvider()
     Sub Component
     LoginComponent accesses any dependencies
     of DaggerAppComponent directly as
     inner class can access outer class members.
     @Singleton
     @ActivityScope
     

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101. DaggerUserComponent
     • schedulerProvider
     • pokemon
     DaggerAppComponent
     • schedulerProvider() : @Singleton
     • userManager : @Singleton
     LoginComponentImpl
     <>
     AppComponent
     fun schedulerProvider()
     HomeComponentImpl
     ItemsComponentImpl
     Dependent Component
     UserComponent accesses any dependencies
     of DaggerAppComponent
     via an interface of AppComponent.
     @Singleton
     @ActivityScope
     @UserScope
     @ActivityScope
     @ActivityScope
     Sub Component
     LoginComponent accesses any dependencies
     of DaggerAppComponent directly as
     inner class can access outer class members.
     

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102. DaggerUserComponent
     • schedulerProvider
     • pokemon
     DaggerAppComponent
     • schedulerProvider() : @Singleton
     • userManager : @Singleton
     LoginComponentImpl
     <>
     AppComponent
     fun schedulerProvider()
     HomeComponentImpl
     ItemsComponentImpl
     @Singleton
     @ActivityScope
     @UserScope
     @ActivityScope
     @ActivityScope
     Sub Component
     LoginComponent accesses any dependencies
     of DaggerAppComponent directly as
     inner class can access outer class members.
     Dependent Component
     UserComponent accesses any dependencies
     of DaggerAppComponent
     via an interface of AppComponent.
     

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103. @ragdroid
     #chicagoroboto
     Custom Scope Advantages
     • Dependency Lifecycle Management
     • Modularized code
     

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104. @ragdroid
     #chicagoroboto
     Some Limitations
     • Repetitive Injection code
     • Class knows about it’s Injector
     

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105. @ragdroid
     #chicagoroboto
     Some Limitations
     Dagger 2 Android
     

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106. DAGGER 2
     ANDROID
     “BEFRIEND THE BEAST”
     

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107. @ragdroid
     #chicagoroboto
     DAHAKA
     APPLICATION
     

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108. class DahakaApplication : Application(), HasActivityInjector {
     @Inject internal lateinit var
     activityInjector: DispatchingAndroidInjector
     …
     override fun activityInjector(): AndroidInjector {
     return activityInjector
     }
     …
     }
     DahakaApplication
     

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109. class DahakaApplication : Application(), HasActivityInjector {
     @Inject internal lateinit var
     activityInjector: DispatchingAndroidInjector
     …
     override fun activityInjector(): AndroidInjector {
     return activityInjector
     }
     …
     }
     DahakaApplication
     

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110. class DahakaApplication : Application(), HasActivityInjector {
     @Inject internal lateinit var
     activityInjector: DispatchingAndroidInjector
     …
     override fun activityInjector(): AndroidInjector {
     return activityInjector
     }
     …
     }
     DahakaApplication
     

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111. HasActivityInjector
     class DahakaApplication : Application(), HasActivityInjector {
     @Inject internal lateinit var
     activityInjector: DispatchingAndroidInjector
     …
     override fun activityInjector(): AndroidInjector {
     return activityInjector
     }
     …
     }
     DahakaApplication
     

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112. @ragdroid
     #chicagoroboto
     APP COMPONENT
     

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113. @Singleton
     @Component(modules = arrayOf(AppModule::class, ApiModule::class,
     AppBindingModule::class, AndroidSupportInjectionModule::class))
     interface AppComponent : AndroidInjector {
     …
     }
     AppComponent
     

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114. AppBindingModule
     @Singleton
     @Component(modules = arrayOf(AppModule::class, ApiModule::class,
     AppBindingModule::class, AndroidSupportInjectionModule::class))
     interface AppComponent : AndroidInjector {
     …
     }
     AppComponent
     

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115. @Module
     abstract class AppBindingModule {
     @ContributesAndroidInjector(modules = arrayOf(LoginModule::class))
     @ActivityScope
     internal abstract fun loginActivity(): LoginActivity
     }
     AppBindingModule
     

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116. @ContributesAndroidInjector
     @Module
     abstract class AppBindingModule {
     @ContributesAndroidInjector(modules = arrayOf(LoginModule::class))
     @ActivityScope
     internal abstract fun loginActivity(): LoginActivity
     }
     AppBindingModule
     

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117. @Module
     abstract class AppBindingModule {
     @ContributesAndroidInjector(modules = arrayOf(LoginModule::class))
     @ActivityScope
     internal abstract fun loginActivity(): LoginActivity
     }
     AppBindingModule
     No need to create LoginActivitySubcomponent class in the above case.
     @ContributesAndroidInjector
     AppBindingModule
     

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118. @Module
     abstract class AppBindingModule {
     @ContributesAndroidInjector(modules = arrayOf(LoginModule::class))
     @ActivityScope
     internal abstract fun loginActivity(): LoginActivity
     }
     AppBindingModule
     @Module
     abstract class LoginModule {
     @Binds
     abstract fun provideLoginPresenter(loginPresenter: LoginPresenter):
     LoginContract.Presenter
     }
     LoginModule
     

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119. @Module(subcomponents = LoginActivitySubcomponent.class)
     public abstract class AppBindingModule_LoginActivity {
     @Binds
     @IntoMap
     @ActivityKey(LoginActivity.class)
     abstract AndroidInjector.Factory extends Activity> bindAndroidInjectorFactory(
     LoginActivitySubcomponent.Builder builder);
     @Subcomponent(modules = LoginModule.class)
     @ActivityScope
     public interface LoginActivitySubcomponent extends AndroidInjector {
     @Subcomponent.Builder
     abstract class Builder extends AndroidInjector.Builder {}
     }
     }
     LoginBindingModule(Generated)
     

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120. @Module(subcomponents = LoginActivitySubcomponent.class)
     public abstract class AppBindingModule_LoginActivity {
     @Binds
     @IntoMap
     @ActivityKey(LoginActivity.class)
     abstract AndroidInjector.Factory extends Activity> bindAndroidInjectorFactory(
     LoginActivitySubcomponent.Builder builder);
     @Subcomponent(modules = LoginModule.class)
     @ActivityScope
     public interface LoginActivitySubcomponent extends AndroidInjector {
     @Subcomponent.Builder
     abstract class Builder extends AndroidInjector.Builder {}
     }
     }
     LoginBindingModule(Generated)
     

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121. @Module(subcomponents = LoginActivitySubcomponent.class)
     public abstract class AppBindingModule_LoginActivity {
     @Binds
     @IntoMap
     @ActivityKey(LoginActivity.class)
     abstract AndroidInjector.Factory extends Activity> bindAndroidInjectorFactory(
     LoginActivitySubcomponent.Builder builder);
     @Subcomponent(modules = LoginModule.class)
     @ActivityScope
     public interface LoginActivitySubcomponent extends AndroidInjector {
     @Subcomponent.Builder
     abstract class Builder extends AndroidInjector.Builder {}
     }
     }
     LoginBindingModule(Generated)
     

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122. @Module(subcomponents = LoginActivitySubcomponent.class)
     public abstract class AppBindingModule_LoginActivity {
     @Binds
     @IntoMap
     @ActivityKey(LoginActivity.class)
     abstract AndroidInjector.Factory extends Activity> bindAndroidInjectorFactory(
     LoginActivitySubcomponent.Builder builder);
     @Subcomponent(modules = LoginModule.class)
     @ActivityScope
     public interface LoginActivitySubcomponent extends AndroidInjector {
     @Subcomponent.Builder
     abstract class Builder extends AndroidInjector.Builder {}
     }
     }
     LoginBindingModule(Generated)
     

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123. @Module(subcomponents = LoginActivitySubcomponent.class)
     public abstract class AppBindingModule_LoginActivity {
     @Binds
     @IntoMap
     @ActivityKey(LoginActivity.class)
     abstract AndroidInjector.Factory extends Activity> bindAndroidInjectorFactory(
     LoginActivitySubcomponent.Builder builder);
     @Subcomponent(modules = LoginModule.class)
     @ActivityScope
     public interface LoginActivitySubcomponent extends AndroidInjector {
     @Subcomponent.Builder
     abstract class Builder extends AndroidInjector.Builder {}
     }
     }
     LoginBindingModule(Generated)
     

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124. @ragdroid
     #chicagoroboto
     LOGIN ACTIVITY
     

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125. public class LoginActivity {
     @Inject
     LoginContract.Presenter presenter;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
     AndroidInjection.inject(this);
     }
     }
     LoginActivity
     

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126. AndroidInjection.inject(LoginActivity)
     LoginActivity
     public class LoginActivity {
     @Inject
     LoginContract.Presenter presenter;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
     AndroidInjection.inject(this);
     }
     }
     

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127. AndroidInjection.inject(LoginActivity)
     AndroidInjection.inje
     

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128. AndroidInjection.inject(LoginActivity)
     AndroidInjection.inje
     AndroidInjection
     

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129. AndroidInjection.inject(LoginActivity)
     AndroidInjection.inje
     AndroidInjection DaggerAppComponent
     

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130. AndroidInjection.inject(LoginActivity)
     AndroidInjection.inje
     AndroidInjection DaggerAppComponent AppBindingModule_LoginActivity
     DispatchingAndroidInjector
     

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131. AndroidInjection.inject(LoginActivity)
     AndroidInjection.inje
     AndroidInjection DaggerAppComponent AppBindingModule_LoginActivity
     DispatchingAndroidInjector
     

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132. AndroidInjection.inject(LoginActivity)
     AndroidInjection.inje
     AndroidInjection DaggerAppComponent AppBindingModule_LoginActivity
     DispatchingAndroidInjector
     ApiModule_ProvideRetrofitFactory
     AppModule_ProviderSchedulerProviderFactory
     ApiModule_ProvidePokemonServiceFactory
     ApiModule_ProvideRetrofitFactory
     AppModule_ProviderSchedulerProviderFactory
     ApiModule_ProvidePokemonServiceFactory
     

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133. @ragdroid
     #chicagoroboto
     BEFRIEND THE BEAST
     “You can not change your fate,
     No droid can.”
     

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134. public interface HasActivityInjector {
     AndroidInjector activityInjector();
     }
     HasActivityInjector
     

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135. HasActivityInjector
     • A simple interface.
     • Implementing class “Has” ActivityInjector.
     public interface HasActivityInjector {
     AndroidInjector activityInjector();
     }
     

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136. HasActivityInjector
     <>
     HasActivityInjector
     fun activityInjector() :
     AndroidInjector
     

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137. HasActivityInjector
     <>
     HasActivityInjector
     fun activityInjector() :
     AndroidInjector
     DahakaApplication
     • activityInjector :
     DispatchingAndroidInjector
     

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138. HasActivityInjector
     <>
     HasActivityInjector
     fun activityInjector() :
     AndroidInjector
     DahakaApplication
     • activityInjector :
     DispatchingAndroidInjector
     <>
     AndroidInjector
     fun inject(Activity instance)
     

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139. HasActivityInjector
     <>
     HasActivityInjector
     fun activityInjector() :
     AndroidInjector
     DahakaApplication
     • activityInjector :
     DispatchingAndroidInjector
     DispatchingAndroidInjector
     • inject(Activity activity)
     • injectorFactories : Map
     <>
     AndroidInjector
     fun inject(Activity instance)
     

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140. DispatchingAndroidInjector
     Provider
     LoginActivity.class
     Class Provider
     DispatchingAndroidInject
     • gets the Subcomponent.Builder from injectorFactory.
     • creates an instance using Builder.
     • calls component.inject(instance) to perform injections.
     • Injects members for Android types : Activity, Fragment, etc
     • Has a Map> injectorFactories.
     

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141. AndroidInjection.inject(LoginActivity)
     

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142. AndroidInjection.inject(LoginActivity)
     activity
     .getApplication()
     LoginActivity
     

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143. AndroidInjection.inject(LoginActivity)
     activity
     .getApplication()
     LoginActivity
     application
     .activityInjector()
     DahakaApplication : HasActivityInjector
     

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144. AndroidInjection.inject(LoginActivity)
     activity
     .getApplication()
     LoginActivity
     application
     .activityInjector()
     DahakaApplication : HasActivityInjector
     activityInjector
     .inject(activity)
     DispatchingAndroidInjector : AndroidInjector
     

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145. AndroidInjection.inject(LoginActivity)
     activity
     .getApplication()
     LoginActivity
     application
     .activityInjector()
     DahakaApplication : HasActivityInjector
     activityInjector
     .inject(activity)
     DispatchingAndroidInjector : AndroidInjector
     

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146. DispatchingAndroidInjector.inject(LoginActivity)
     injectorFactories
     .get(LoginActivity.class)
     DispatchingAndroidInjector : AndroidInjector
     

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147. DispatchingAndroidInjector : AndroidInjector
     Factory : LoginSubcomponent.Builder
     injectorFactories
     .get(LoginActivity.class)
     DispatchingAndroidInjector.inject(LoginActivity)
     builder
     .build()
     

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148. DispatchingAndroidInjector : AndroidInjector
     Factory : LoginSubcomponent.Builder
     component
     .inject(activity)
     LoginSubcomponent
     injectorFactories
     .get(LoginActivity.class)
     DispatchingAndroidInjector.inject(LoginActivity)
     builder
     .build()
     

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149. DispatchingAndroidInjector : AndroidInjector
     builder
     .build()
     Factory : LoginSubcomponent.Builder
     component
     .inject(activity)
     LoginSubcomponent
     DispatchingAndroidInjector.inject(LoginActivity)
     injectorFactories
     .get(LoginActivity.class)
     

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150. • DaggerApplication
     • DaggerActivity
     • DaggerBroadcastReceiver
     • DaggerContentProvider
     • DaggerFragment
     • DaggerIntentService
     • DaggerService
     Dagger Boilerplate classes
     

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151. @ragdroid
     #chicagoroboto
     Dagger 2 Android = Dahaka
     • D
     • A
     • H
     • A
     • K
     • A
     Dagger
     Android
     HasActivityInjector
     AndroidInjection
     Keys
     AndroidInjector
     

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152. @ragdroid
     #chicagoroboto
     Dagger 2 Android
     “You can not change your fate,
     No droid can”
     Let’s befriend the beast instead.
     

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153. @ragdroid
     #chicagoroboto
     LOGIN ACTIVITY
     

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154. AndroidInjection.inject(LoginActivity)
     LoginActivity
     public class LoginActivity {
     @Inject
     LoginContract.Presenter presenter;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
     val appComponent = ((application as DahakaApplication)
     .appComponent)
     loginComponent = appComponent
     .loginBuilder()
     .loginActivity(this)
     .build()
     loginComponent.inject(this)
     }
     }
     

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155. LoginActivity
     public class LoginActivity {
     @Inject
     LoginContract.Presenter presenter;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
     AndroidInjection.inject(this);
     }
     }
     

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156. What Next?
     • Dagger Documentation :
     https://google.github.io/dagger//
     • todo-mvp-dagger : Mike Nakhimovich (@friendlyMikhail )
     https://github.com/googlesamples/android-architecture/tree/todo-mvp-dagger
     • Dagger Example
     https://github.com/ragdroid/Dahaka
     • Testing article
     https://android.jlelse.eu/testing-your-app-with-dagger-2-c91cdc0860fb
     • Dagger and the Dahaka Series :
     https://medium.com/@ragdroid
     

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157. Acknowledgements
     • Dagger Recipies : Miroslaw Stanek (@froger_mcs)
     https://about.me/froger_mcs
     • todo-mvp-dagger : Mike Nakhimovich (@friendlyMikhail )
     https://github.com/googlesamples/android-architecture/tree/todo-mvp-dagger
     • Android Dialogs : Mike Nakhimovich
     https://www.youtube.com/watch?v=KwRXQ6nT7jQ
     • Proof Reading : Ritesh Gupta (@_riteshhh)
     • Migrate to Kotlin : Ravindra Kumar (@ravidsrk)
     

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158. Demo Code
     • Dahaka Demo :
     https://github.com/ragdroid/Dahaka
     • Branches :
     • dagger-android : Pokemon app using dagger-android (With Tests, Fragments)
     • dagger-android-dependent-comp-kotlin : dagger-android with Dependent Component
     • subcomponent : UserComponent as subcomponent
     • dependent-component-kotlin : UserComponent as dependent component
     

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159. Other References
     • Theme : Prince of Persia https://en.wikipedia.org/wiki/Prince_of_Persia
     • Dahaka https://files.gamebanana.com/img/ico/sprays/dahaka.png
     • Dagger https://in.pinterest.com/pin/397442735844321339/
     • Android http://www.pngmart.com/files/4/Android-PNG-Image.png
     

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160. @ragdroid
     #chicagoroboto
     CUT
     SCENES
     

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161. Dagger 2 Android
     “Defeat the Dahaka"
     Garima Jain
     @ragdroid
     

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162. Dagger 2 Android
     “Defeat the Dahaka"
     Garima Jain
     @ragdroid
     

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163. FUELED
     http://fueled.com/garima
     garima@fueled.com
     THANK YOU
     

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164. FUELED
     http://fueled.com/garima
     garima@fueled.com
     Q & A
     @ragdroid
     

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