Dagger 2.0 New dependency injection for Android Radosław Piekarz 

Spring ● Popular in the Java community ● Polularized DI/IoC ● XML configuration 

Guice / RoboGuice ● Used new features in Java 1.5 ● No XML configuration ● Not so easy to debug ● Runtime validation 

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Dagger 1 ● Compile time validation ● Do more work during compile and less in runtime ● Faster than Guice/RoboGuice 

Dagger 1 ● Not proguard safe ● Runtime graph composition 

Source: Jake Wharton 

Minimal graph creation time - not just fast, but hand-written DI fast 

Full, static inspection of code paths 

No reflection, no explicit classloading 

Dagger 2 API ● @Module & @Provides - mechanism for providing dependencies ● @Inject - mechanism for requesting dependencies ● @Component bridge between modules and injections 

Example module @Module class PumpModule { @Provides Pump providePump(Thermosiphon pump) { return pump; } } 

@Inject class CoffeeMaker { private final Lazy heater; private final Pump pump; @Inject CoffeeMaker(Lazy heater, Pump pump) { this.heater = heater; this.pump = pump; } 

@Component @Component(modules = {DripCoffeeModule.class}) public interface Coffee { CoffeeMaker maker(); } 

Example app public class CoffeeApp { public static void main(String[] args) { Coffee coffee = Dagger_Coffee.builder() .build(); coffee.maker().brew(); } } 

Dagger 1 vs Dagger 2 public class CoffeeApp implements Runnable { @Inject CoffeeMaker coffeeMaker; @Override public void run() { coffeeMaker.brew(); } public static void main(String[] args) { ObjectGraph objectGraph = ObjectGraph.create(new DripCoffeeModule()); CoffeeApp coffeeApp = objectGraph.get(CoffeeApp.class); coffeeApp.run(); } } 

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Quick demos 

u2020 & u2021 https://github.com/Jak eWharton/u2020 https://github.com/cgr uber/u2020/tree/dagg er2 

Dagger 2 Pros ● It is really fast ● Compile time validation for entire graph ● Easy debugging Cons ● Not flexible ● There is no dynamism 

https://github.com/google/dagger/ https://google.github.io/dagger/ 

Q&A Thank you for your attention! radzio RadoslawPiekarz { }