Getting Started with Dagger 2

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Getting Started with Dagger 2 Fast dependency injection for Android applications

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Why dependency injection? Separation of concerns Testability Every app has some kind of dependency injection

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Uncle Bob “Depend upon Abstractions. Do not depend upon concretions.”

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A brief history of time JSR-330 Guice Dagger

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Dagger 2 Maintained by Java Core Libraries team at Google Faster than Guice and Dagger Easy to use and to debug Mobile ﬁrst

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Dagger API @Modules + @Provides @Inject @Component

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Providing Dependencies

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Requesting Dependencies @Inject annotations required Constructor, Field & Method

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Constructor Injection @Inject on a single constructor Parameters are dependencies They can be stored in private and ﬁnal ﬁelds

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Constructor Injection

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Constructor Injection It’s useless now

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Constructor Injection

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Dependency Graph EpisodeRepository DataModule#provideEpisodeRepository RemoteEpisodeRepository TraktvApi DataModule#provideTraktvApi OmdbApi DataModule#provideOmdbApi Constructor Injection

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Field Injection @Inject on ﬁelds for dependencies Field can not be private or ﬁnal Inject happens after object is fully instantiated Object is usually responsible for injection

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Method Injection

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http://google.github.io/dagger/

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Components Bridge between modules and injections The injector

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Components

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Components this notation is optional

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Components

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Components

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How about some live coding?

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github.com/google/dagger

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Questions?

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Questions? github.com/rodrigohenriques

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