Optimizing Dagger on Android

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Optimizing Dagger on Android Ron Shapiro ronsh@google @rdshapiro

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Prereqs

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Prereqs ● You've used Dagger before

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Prereqs ● You've used Dagger before ● Optional: Understanding Dagger 2's Generated Code ○ https://goo.gl/toV6Nq

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Prereqs ● You've used Dagger before ● Optional: Understanding Dagger 2's Generated Code ○ https://goo.gl/toV6Nq ● You’re not scared to look at generated code

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Glossary

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Glossary ● Key ! Type + Optional

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Glossary ● Key ! Type + Optional ● Binding ! Key + ImmutableSet

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Glossary ● Key ! Type + Optional ● Binding ! Key + ImmutableSet @Provides  Airplane airplane(

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Glossary ● Key ! Type + Optional ● Binding ! Key + ImmutableSet @Provides  Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }

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Glossary ● Key ! Type + Optional ● Binding ! Key + ImmutableSet @Provides  Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … } ● DependencyRequest ! Key + Kind

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Glossary ● Key ! Type + Optional ● Binding ! Key + ImmutableSet @Provides  Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … } ● DependencyRequest ! Key + Kind ○ enum Kind { INSTANCE, PROVIDER, LAZY, … }

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Glossary ● Key ! (normalized) Type + Optional ● Binding ! Key + ImmutableSet @Provides  Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1 ● DependencyRequest ! Key + Kind ○ enum Kind { INSTANCE, PROVIDER, LAZY, … }

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Glossary ● Key ! (normalized) Type + Optional ● Binding ! Key + ImmutableSet @Provides  Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1   @Provides  XWing xWing( Body body, @Left Wing left, @Right Wing right) { … } ● DependencyRequest ! Key + Kind ○ enum Kind { INSTANCE, PROVIDER, LAZY, … }

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Glossary ● Key ! (normalized) Type + Optional ● Binding ! Key + ImmutableSet @Provides  Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1   @Provides  XWing xWing( Body body, @Left Provider left, @Right Provider right) { … } ● DependencyRequest ! Key + Kind ○ enum Kind { INSTANCE, PROVIDER, LAZY, … }

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Glossary ● Key ! (normalized) Type + Optional ● Binding ! Key + ImmutableSet @Provides  Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1   @Provides  XWing xWing( Body body, @Left Provider left, @Right Provider right, Logo logo) { … } ● DependencyRequest ! Key + Kind ○ enum Kind { INSTANCE, PROVIDER, LAZY, … }

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Glossary ● Key ! (normalized) Type + Optional ● Binding ! Key + ImmutableSet @Provides  Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1   @Provides  XWing xWing( Body body, @Left Provider left, @Right Provider right, Lazy logo) { … } ● DependencyRequest ! Key + Kind ○ enum Kind { INSTANCE, PROVIDER, LAZY, … }

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Life of a DependencyRequest java/dagger/internal/codegen/BindingExpression.java

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Life of a DependencyRequest ● How many bindings have this key? java/dagger/internal/codegen/BindingExpression.java

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Life of a DependencyRequest ● How many bindings have this key? ○ 0 ! missing binding error java/dagger/internal/codegen/BindingExpression.java

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Life of a DependencyRequest ● How many bindings have this key? ○ 0 ! missing binding error ○ 2+ ! duplicate binding error java/dagger/internal/codegen/BindingExpression.java

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Life of a DependencyRequest ● How many bindings have this key? ○ 0 ! missing binding error ○ 2+ ! duplicate binding error java/dagger/internal/codegen/BindingExpression.java

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Life of a DependencyRequest ● How many bindings have this key? ○ 0 ! missing binding error ○ 2+ ! duplicate binding error ● How can Binding X be represented as DependencyRequest.Kind Y using X's own dependencies? java/dagger/internal/codegen/BindingExpression.java

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@Module class AirplaneModule { @Provides Airplane weldAndCreate() {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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@Module class AirplaneModule { @Provides Airplane weldAndCreate(Body body) {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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@Module class AirplaneModule { @Provides Airplane weldAndCreate( Body body, @Left Wing leftWing, @Right Wing rightWing) {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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@Module class AirplaneModule { @Provides Airplane weldAndCreate( Body body, @Left Wing leftWing, @Right Wing rightWing, Welder welder) {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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@Module class AirplaneModule { @Provides Airplane weldAndCreate( Body body, @Left Wing leftWing, @Right Wing rightWing, Welder welder, Lazy lazySafety) {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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@Module class AirplaneModule { @Provides Airplane weldAndCreate( Body body, @Left Wing leftWing, @Right Wing rightWing, Welder welder, Lazy lazySafety) { welder.weld(body, leftWing); welder.weld(body, rightWing); if (LAWYERS_REQUIRE_SAFETY_FEATURE) { lazySafety.get().protect(body); } return new Airplane(body); }1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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Life of a DependencyRequest @Component(modules = { AirplaneModule.class, WingModule.class, }) interface AirplaneComponent { Airplane createAirplane(); }

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Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1/* body */,2 1/* left wing */, 1/* right wing */, 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(),2 1/* left wing */, 1/* right wing */, 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1/* left wing */, 1/* right wing */, 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1/* right wing */, 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java

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Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1welderProvider.get(), 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java java/dagger/internal/codegen/FrameworkType.java

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Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1welderProvider.get() /* */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java java/dagger/internal/codegen/FrameworkType.java

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Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1welderProvider.get() /* */, 1DoubleCheck.lazy(safetyProvider); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java java/dagger/internal/codegen/FrameworkType.java

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Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1welderProvider.get() /* */, 1DoubleCheck.lazy(safetyProvider /* */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java java/dagger/internal/codegen/FrameworkType.java

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Life of a component initialization private void initialize() { this.welderProvider =1 }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java

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Life of a component initialization private void initialize() { this.welderProvider =1 new Provider() { @Override public Welder get()3{}4 }; }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java

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Life of a component initialization private void initialize() { this.welderProvider =15 6new Provider() { @Override public Welder get()3{ return new Welder( new Wire(), new ProtectiveShield(), flamethrowerProvider.get()); }4 }; }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java

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Life of a component initialization private void initialize() { this.welderProvider =1DoubleCheck.provider(5 6new Provider() { @Override public Welder get()3{ return new Welder( new Wire(), new ProtectiveShield(), flamethrowerProvider.get()); }4 }); }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java

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Life of a component initialization private void initialize() { this.welderProvider =1DoubleCheck.provider(5 6new Provider() { ^ error: [MemoryLeak] this might leak your *entire* component! @Override public Welder get()3{ return new Welder( new Wire(), new ProtectiveShield(), flamethrowerProvider.get()); }4 }); }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java ^ shameless plug for ErrorProne github.com/google/error-prone

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Life of a component initialization java/dagger/internal/codegen/FrameworkFieldInitializer.java

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Life of a component initialization private void initialize() { java/dagger/internal/codegen/FrameworkFieldInitializer.java

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Life of a component initialization private void initialize() { this.wireProvider = Wire_Factory.create(); java/dagger/internal/codegen/FrameworkFieldInitializer.java

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Life of a component initialization private void initialize() { this.wireProvider = Wire_Factory.create(); this.protectiveShieldProvider =  ProtectiveShield_Factory.create(); this.welderProvider = DoubleChecker.provider(  Welder_Factory.create(  wireProvider,  protectiveShieldProvider,  flamethrowerProvider)); java/dagger/internal/codegen/FrameworkFieldInitializer.java

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Life of a component initialization private void initialize() { this.wireProvider = Wire_Factory.create(); this.protectiveShieldProvider =  ProtectiveShield_Factory.create(); this.welderProvider = DoubleChecker.provider(  Welder_Factory.create(  wireProvider,  protectiveShieldProvider,  flamethrowerProvider)); } java/dagger/internal/codegen/FrameworkFieldInitializer.java

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Why does this matter?

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tl;dr: component initialization is

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tl;dr: component initialization is s l o w

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But just how slow is it? Activity component measurements initialization time

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But just how slow is it? 200ms Activity component measurements initialization time init #1

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But just how slow is it? 200ms 2 ms Activity component measurements initialization time init #1 init #2+

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But just how slow is it? 200ms 2 ms 102! Activity component measurements initialization time init #1 init #2+

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But just how slow is it? 200ms 2 ms 102! Activity component measurements initialization time What is happening here? init #1 init #2+

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But just how slow is it? 200ms 2 ms 102! Activity component measurements initialization time What is happening here? Answer: class loading init #1 init #2+

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How can we load fewer classes?

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How can we load fewer classes? ● com.google.dagger:dagger-compiler:2.12

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How can we load fewer classes? ● com.google.dagger:dagger-compiler:2.12 ○ coming very soon!

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Dagger 2.12 Bindings Provider form Inlined form java/dagger/internal/codegen/SetBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoSet T single() { … } @Provides @ElementsIntoSet Set many() { … } java/dagger/internal/codegen/SetBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoSet T single() { … } @Provides @ElementsIntoSet Set many() { … } SetFactory.builder() .add(Single_Factory.create()) .addAll(Many_Factory.create()) .build(); java/dagger/internal/codegen/SetBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoSet T single() { … } @Provides @ElementsIntoSet Set many() { … } SetFactory.builder() .add(Single_Factory.create()) .addAll(Many_Factory.create()) .build(); ImmutableSet.builder() .add(single()) .addAll(many()) .build(); java/dagger/internal/codegen/SetBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form java/dagger/internal/codegen/MapBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoMap @IntKey(1) V first() { … } @Provides @IntoMap @IntKey(2) V second() { … } java/dagger/internal/codegen/MapBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoMap @IntKey(1) V first() { … } @Provides @IntoMap @IntKey(2) V second() { … } MapFactory.builder() .put(1, First_Factory.create()) .put(2, Second_Factory.create()) .build(); java/dagger/internal/codegen/MapBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoMap @IntKey(1) V first() { … } @Provides @IntoMap @IntKey(2) V second() { … } MapFactory.builder() .put(1, First_Factory.create()) .put(2, Second_Factory.create()) .build(); ImmutableMap.builder() .put(1, first()) .put(2, second()) .build(); java/dagger/internal/codegen/MapBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form java/dagger/internal/codegen/OptionalBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @BindsOptionalOf DebugLogger sometimes(); java/dagger/internal/codegen/OptionalBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @BindsOptionalOf DebugLogger sometimes(); new Provider>() { @Override public Optional get() { return Optional.of(debugLoggerProvider.get()); } } java/dagger/internal/codegen/OptionalBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @BindsOptionalOf DebugLogger sometimes(); new Provider>() { @Override public Optional get() { return Optional.of(debugLoggerProvider.get()); } } Optional.of(DebugModule.logger()); java/dagger/internal/codegen/OptionalBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form java/dagger/internal/codegen/ComponentProvisionBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @Component @Component( interface DatabaseComponent { dependencies = DatabaseComponent.class) Database database(); interface NetworkingComponent { } UsesDatabase usesDatabase(); } java/dagger/internal/codegen/ComponentProvisionBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @Component @Component( interface DatabaseComponent { dependencies = DatabaseComponent.class) Database database(); interface NetworkingComponent { } UsesDatabase usesDatabase(); } new Provider() { @Override public Database get() { return databaseComponent.database(); } }; java/dagger/internal/codegen/ComponentProvisionBindingExpression.java

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Dagger 2.12 Bindings Provider form Inlined form @Component @Component( interface DatabaseComponent { dependencies = DatabaseComponent.class) Database database(); interface NetworkingComponent { } UsesDatabase usesDatabase(); } new Provider() { @Override public Database get() { return databaseComponent.database(); } }; databaseComponent.database(); java/dagger/internal/codegen/ComponentProvisionBindingExpression.java

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How can we load fewer classes? ● com.google.dagger:dagger-compiler:2.12 ○ coming very soon!

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How can we load fewer classes? ● com.google.dagger:dagger-compiler:2.12 ○ coming very soon! ● Unnecessary Provider/Lazy usage

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Don't force Dagger's hand public class DroidconScheduleActivity extends Activity { @Inject Provider scheduleProvider; @Override public void onCreate() { scheduleView.setSchedule(scheduleProvider.get()); } }

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Don't force Dagger's hand

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Don't force Dagger's hand If you inject…

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Don't force Dagger's hand If you inject… || Provider

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Don't force Dagger's hand If you inject… || Provider || Lazy

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Don't force Dagger's hand If you inject… || Provider || Lazy

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Don't force Dagger's hand If you inject… || Provider || Lazy And

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Don't force Dagger's hand If you inject… || Provider || Lazy And || you always call get() exactly once (especially in the constructor / onCreate())

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Don't force Dagger's hand If you inject… || Provider || Lazy And || you always call get() exactly once (especially in the constructor / onCreate()) || YourBinding is not expensive to create, but you aren't sure if you need it

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Don't force Dagger's hand public class DroidconScheduleActivity extends Activity { @Inject Lazy lazySchedule; @Override public void onCreate() { scheduleView.setSchedule(lazySchedule.get()); }1 }2

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Don't force Dagger's hand public class DroidconScheduleActivity extends Activity { @Inject Lazy lazySchedule; @Inject Lazy lazySchedule2; @Override public void onCreate() { scheduleView.setSchedule(lazySchedule.get()); }1 }2

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Don't force Dagger's hand public class DroidconScheduleActivity extends Activity { @Inject Lazy lazySchedule; @Inject Lazy lazySchedule2; @Override public void onCreate() { assertThat(lazySchedule.get()) .isNotSameAs(lazySchedule2.get()); }1 }2

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Don't force Dagger's hand @Inject Provider myProvider; YourBinding[] array = new YourBinding[4]; for (i = 0; i < 4; i++) { array[i] = myProvider.get();2 }1

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Don't force Dagger's hand @Inject Provider myProvider; @Injectyb0; @Injectyb1; @Injectyb2; @Injectyb3; YourBinding[] array = new YourBinding[4]; for (i = 0; i < 4; i++) { array[i] = myProvider.get();2 }1

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Don't force Dagger's hand @Inject Provider myProvider; @Injectyb0; @Injectyb1; @Injectyb2; @Injectyb3; YourBinding[] array = {yb0, yb1, yb2, yb3};

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Don't force Dagger's hand @Injectyb0; @Injectyb1; @Injectyb2; @Injectyb3; YourBinding[] array = {yb0, yb1, yb2, yb3};

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How can we load fewer classes? ● com.google.dagger:dagger-compiler:2.12 ○ coming very soon! ● Unnecessary Provider/Lazy usage

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How can we load fewer classes? ● com.google.dagger:dagger-compiler:2.12 ○ coming very soon! ● Unnecessary Provider/Lazy usage ● Reconsider scoping decisions

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Reconsider scoping

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Reconsider scoping @AnalyticsScope  class AnalyticsTracker {

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Reconsider scoping @AnalyticsScope  class AnalyticsTracker { @Inject AnalyticsTracker(  UnsyncedAnalyticsQueue queue,  String flowName,  ViewToAnalyticsIdTranslator viewTranslator) { … }

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Reconsider scoping @AnalyticsScope  class AnalyticsTracker { @Inject AnalyticsTracker(  UnsyncedAnalyticsQueue queue,  String flowName,  ViewToAnalyticsIdTranslator viewTranslator) { … }   void trackClick(View view) {  queue.add(flowName, viewTranslator.translate(view)); }

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Reconsider scoping @AnalyticsScope class AnalyticsTracker { @Inject AnalyticsTracker( UnsyncedAnalyticsQueue queue, String flowName, ViewToAnalyticsIdTranslator viewTranslator) { … } }A

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Reconsider scoping class AnalyticsTracker { @Inject AnalyticsTracker( UnsyncedAnalyticsQueue queue, String flowName, ViewToAnalyticsIdTranslator viewTranslator) { … } }A @AnalyticsScope class UnsyncedAnalyticsQueue {}

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Reconsider scoping @Singleton @Component(modules = ExecutorModule.class) interface NetworkingComponent {Q…Z} @Module abstract class ExecutorModule { @Provides @Singleton @Background Executor provideBackgroundExecutor() { return Executors.newCachedThreadPool(4); } }

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Reconsider scoping @Singleton @Component(modules = ExecutorModule.class) interface NetworkingComponent { Q// …Z }R

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Reconsider scoping @Singleton @Component interface NetworkingComponent { // …Z 1 }R2

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Reconsider scoping @Singleton @Component interface NetworkingComponent { // … [email protected] interface Builder { @BindsInstance Builder executor(Executor e); NetworkingComponent build(); } }R

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How can we load fewer classes? ● com.google.dagger:dagger-compiler:2.12 ○ coming very soon! ● Unnecessary Provider/Lazy usage ● Reconsider scoping decisions

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How can we load fewer classes? ● com.google.dagger:dagger-compiler:2.12 ○ coming very soon! ● Unnecessary Provider/Lazy usage ● Reconsider scoping decisions ● Suggest better codegen strategies ○ github.com/google/dagger/issues

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Dagger on Android Stop making me think about injection

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Dagger on Android public class LoginActivity extends Activity { @Inject OAuthClient oauth; @Inject PasswordEncrypter encrypter; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ((DroidconApp) getApplication()) .getComponent() .inject(this); } }

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Dagger on Android public class DroidconApp extends Application { private DroidconComponent component; public DroidconComponent getComponent() { if (component == null) { component = DaggerDroidconComponent.create(); } return component; } }

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dagger.android public class LoginActivity extends DaggerActivity { @Inject OAuthClient oauth; @Inject PasswordEncrypter encrypter; } public class DroidconApp extends DaggerApplication {} @Module interface LoginModule { @ContributesAndroidInjector LoginActivity configureLoginActivityInjection(); }

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dagger.android ● DaggerActivity ● DaggerFragment ● DaggerService + DaggerIntentService ● DaggerBroadcastReceiver ● DaggerApplication ● DaggerAppCompatActivity ● dagger.android.support.DaggerFragment ● @ContributesAndroidInjector

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dagger.android under the hood @ContributesAndroidInjector(modules = LoginSpecificModule.class) LoginActivity loginActivity(); @Subcomponent(modules = LoginSpecificModule.class) interface LoginActivitySubcomponent extends AndroidInjector { @Subcomponent.Builder abstract class Builder extends AndroidInjector.Builder {} }

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Faster builds w/ Dagger

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Compile as little as possible ● When you have a hammer, everything looks like a @Subcomponent ○ but subcomponents require compilation at the root! ● Break up compilation where possible ○ gradle users: make lots of modules ○ bazel users: split up java_librarys

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Compile as little as possible

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Compile as little as possible @Component(modules = NetworkingModule.class)  interface NetworkingComponent {  OkHttpClient httpClient();  }

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Compile as little as possible @Component(modules = NetworkingModule.class)  interface NetworkingComponent {  OkHttpClient httpClient();  }

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Compile as little as possible @Component(modules = NetworkingModule.class)  interface NetworkingComponent {  OkHttpClient httpClient();  }   @Component(dependencies = NetworkingComponent.class)  interface AppComponent {  ApiService apiService();  }

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Compile as little as possible public final class DaggerAppComponent implements AppComponent { private NetworkingComponent networkComponentDependency; @Override public void ApiService apiService() { return new ApiService(networkComponentDependency.httpClient()); } }