Android Apps with Dagger (Devoxx 2013)

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Dagger Jake Wharton

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#DV13 #Dagger DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger ger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #D #Dagger #DV13 #Dagger #DV13 #Dagg #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger V13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagge #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Da #DV13 #Dagger #DV13 #Dagger #DV13 #Da ger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagge #DV13 #Dagger #DV13 #Dagger V13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger er #D #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #D #DV13 #Dagger #DV13 #Dagg #DV13 #Dagger 13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #D #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger #DV13 #Dagger 3 #Dagger gger #DV13 #Dagger #DV13 #Dagger

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Dependency Injection

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Dependency Injection • Every single app has some form of dependency injection

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Dependency Injection • Every single app has some form of dependency injection • Separate behavior of something from its required classes

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Dependency Injection • Every single app has some form of dependency injection • Separate behavior of something from its required classes Tweeter

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Dependency Injection • Every single app has some form of dependency injection • Separate behavior of something from its required classes Tweeter Twitter API

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Dependency Injection • Every single app has some form of dependency injection • Separate behavior of something from its required classes Tweeter Twitter API HTTP Client

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public class Tweeter { public void tweet(String tweet) { TwitterApi api = new TwitterApi(); api.postTweet("JakeWharton", tweet); } }

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public class Tweeter { public void tweet(String tweet) { TwitterApi api = new TwitterApi(); api.postTweet("JakeWharton", tweet); } } public class TwitterApi { public void postTweet(String user, String tweet) { OkHttpClient client = new OkHttpClient(); HttpUrlConnection conn = client.open("..."); // ... POST blah blah blah ... } }

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public class Tweeter { public void tweet(String tweet) { TwitterApi api = new TwitterApi(); api.postTweet("JakeWharton", tweet); } } Tweeter tweeter = new Tweeter(); tweeter.tweet("Hello, Devoxx 2013! #DV13 #Dagger"); public class TwitterApi { public void postTweet(String user, String tweet) { OkHttpClient client = new OkHttpClient(); HttpUrlConnection conn = client.open("..."); // ... POST blah blah blah ... } }

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public class TwitterApi { public void postTweet(String user, String tweet) { OkHttpClient client = new OkHttpClient(); HttpUrlConnection conn = client.open("..."); // ... POST blah blah blah ... } }

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public class TwitterApi { private final OkHttpClient client = new OkHttpClient(); public void postTweet(String user, String tweet) { HttpUrlConnection conn = client.open("..."); // ... POST blah blah blah ... } }

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public class TwitterApi { private final OkHttpClient client; public TwitterApi(OkHttpClient client) { this.client = client; } public void postTweet(String user, String tweet) { HttpUrlConnection conn = client.open("..."); // ... POST blah blah blah ... } }

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public class Tweeter { public void tweet(String tweet) { TwitterApi api = new TwitterApi(); api.postTweet("JakeWharton", tweet); } }

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public class Tweeter { public void tweet(String tweet) { TwitterApi api = new TwitterApi(new OkHttpClient()); api.postTweet("JakeWharton", tweet); } }

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public class Tweeter { private final TwitterApi api = new TwitterApi(new OkHttpClient()); public void tweet(String tweet) { api.postTweet("JakeWharton", tweet); } }

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public class Tweeter { private final TwitterApi api = new TwitterApi(new OkHttpClient()); private final String user; public Tweeter(String user) { this.user = user; } public void tweet(String tweet) { api.postTweet(user, tweet); } }

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Tweeter tweeter = new Tweeter(); tweeter.tweet("Hello, Devoxx 2013! #DV13 #Dagger");

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Tweeter tweeter = new Tweeter("JakeWharton"); tweeter.tweet("Hello, Devoxx 2013! #DV13 #Dagger");

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Tweeter tweeter = new Tweeter("JakeWharton"); tweeter.tweet("Hello, Devoxx 2013! #DV13 #Dagger"); tweeter.tweet("Devoxx 2013 is amazing! #DV13"); tweeter.tweet("mind == blown. #DV13 #Dagger"); tweeter.tweet("OMG you better be at Devoxx!"); tweeter.tweet("#Devoxx #Dagger #Devoxx #Dagger #Devoxx"); tweeter.tweet("Hungover... #DV13");

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public class Timeline { private final List tweetCache = new ArrayList<>(); private final TwitterApi api = new TwitterApi(new OkHttpClient()); private final String user; public Timeline(String user) { this.user = user; } public List get() { /* ... */ } public void loadMore(int amount) { /* ... */ } }

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public class Timeline { private final List tweetCache = new ArrayList<>(); private final TwitterApi api; private final String user; public Timeline(TwitterApi api, String user) { this.api = api; this.user = user; } public List get() { /* ... */ } public void loadMore(int amount) { /* ... */ } }

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public class Tweeter { private final TwitterApi api; private final String user; public Tweeter(TwitterApi api, String user) { this.api = api; this.user = user; } public void tweet(String tweet) { api.postTweet(user, tweet); } }

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Tweeter tweeter = new Tweeter("JakeWharton"); tweeter.tweet("Hello, Devoxx 2013!"); Timeline timeline = new Timeline("JakeWharton"); timeline.loadMore(20); for (Tweet tweet : timeline.get()) { System.out.println(tweet); }

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OkHttpClient client = new OkHttpClient(); TwitterApi api = new TwitterApi(client); String user = "JakeWharton"; Tweeter tweeter = new Tweeter(api, user); tweeter.tweet("Man, this takes a lot of code!"); Timeline timeline = new Timeline(api, user); timeline.loadMore(20); for (Tweet tweet : timeline.get()) { System.out.println(tweet); }

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Dependency Injection • Every single app has some form of dependency injection • Separate the behavior from the classes required to perform it Tweeter Twitter API HTTP Client

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Dependency Injection • Every single app has some form of dependency injection • Separate the behavior from the classes required to perform it Tweeter Twitter API HTTP Client Timeline

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Dependency Injection • Every single app has some form of dependency injection • Separate the behavior from the classes required to perform it • How do we avoid the boilerplate that comes with the pattern?

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We used Guice

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We used Guice • All of our Java services heavily use Guice

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We used Guice • All of our Java services heavily use Guice • Powerful, dynamic, well-tested, wide-spread, etc...

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We used Guice • All of our Java services heavily use Guice • Powerful, dynamic, well-tested, wide-spread, etc... • Canonical standard for dependency injection

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We used Guice • All of our Java services heavily use Guice • Powerful, dynamic, well-tested, wide-spread, etc... • Canonical standard for dependency injection • Conﬁguration problems fail at runtime

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“ObjectGraph” Goals

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“ObjectGraph” Goals • Static analysis of all dependencies and injections

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“ObjectGraph” Goals • Static analysis of all dependencies and injections • Fail as early as possible (compile-time, not runtime)

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“ObjectGraph” Goals • Static analysis of all dependencies and injections • Fail as early as possible (compile-time, not runtime) • Eliminate reflection on methods and annotations at runtime

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“ObjectGraph” Goals • Static analysis of all dependencies and injections • Fail as early as possible (compile-time, not runtime) • Eliminate reflection on methods and annotations at runtime • Have negligible memory impact

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“ObjectGraph” Development

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“ObjectGraph” Development • ~5 weeks of heads-down work by Jesse Wilson

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“ObjectGraph” Development • ~5 weeks of heads-down work by Jesse Wilson • Bob Lee served as technical advisor

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“ObjectGraph” Development • ~5 weeks of heads-down work by Jesse Wilson • Bob Lee served as technical advisor • “Giant” boolean switch in our applications

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“ObjectGraph” Development • ~5 weeks of heads-down work by Jesse Wilson • Bob Lee served as technical advisor • “Giant” boolean switch in our applications • 2 weeks after, dropped Guice completely

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Dagger

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Dagger Tweeter Twitter API HTTP Client User Manager Shared Preferences Account Manager

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Dagger Tweeter Twitter API HTTP Client User Manager Shared Preferences DAG-er Account Manager

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Dagger

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Dagger • ObjectGraph: central dependency manager and injector

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Dagger • ObjectGraph: central dependency manager and injector • @Module + @Provides: mechanism for providing dependencies

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Dagger • ObjectGraph: central dependency manager and injector • @Module + @Provides: mechanism for providing dependencies • @Inject: mechanism for requesting dependencies

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Dagger • ObjectGraph: central dependency manager and injector • @Module + @Provides: mechanism for providing dependencies • @Inject: mechanism for requesting dependencies • Plus some other sugar, magic, and conventions

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Providing Dependencies

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Providing Dependencies • Modules are classes that provide dependencies

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Providing Dependencies • Modules are classes that provide dependencies • @Module annotation on the class

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Providing Dependencies • Modules are classes that provide dependencies • @Module annotation on the class • @Provider annotation on a method indicates that its return type is a dependency

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public class NetworkModule { public OkHttpClient provideOkHttpClient() { return new OkHttpClient(); } public TwitterApi provideTwitterApi(OkHttpClient client) { return new TwitterApi(client); } }

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public class NetworkModule { public OkHttpClient provideOkHttpClient() { return new OkHttpClient(); } public TwitterApi provideTwitterApi(OkHttpClient client) { return new TwitterApi(client); } } @Module

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Providing Dependencies

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Providing Dependencies OkHttpClient TwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies • Modules are classes that provide dependencies • @Module annotation on the class provides static analysis hints • @Provider annotation on a method indicates that its return type is a dependency

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@Module public class TwitterModule { private final String user; public TwitterModule(String user) { this.user = user; } @Provides @Singleton public Tweeter provideTweeter(TwitterApi api) { return new Tweeter(api, user); } @Provides @Singleton public Timeline provideTimeline(TwitterApi api) { return new Timeline(api, user); } }

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi Tweeter Timeline TwitterModule#provideTweeter TwitterModule#provideTimeline

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Requesting Dependencies

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Requesting Dependencies • @Inject annotation required

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Requesting Dependencies • @Inject annotation required • Field injection and constructor injection only

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Constructor Injection

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Constructor Injection • @Inject on a single constructor

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Constructor Injection • @Inject on a single constructor • All constructor arguments are dependencies

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Constructor Injection • @Inject on a single constructor • All constructor arguments are dependencies • Dependencies can be stored in private and final ﬁelds

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public class TweeterApp { private final Tweeter tweeter; private final Timeline timeline; @Inject public TweeterApp(Tweeter tweeter, Timeline timeline) { this.tweeter = tweeter; this.timeline = timeline; } // ... }

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Constructor Injection • @Inject on a single constructor • All constructor arguments are dependencies • Dependencies can be stored in private and final ﬁelds

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Constructor Injection • @Inject on a single constructor • All constructor arguments are dependencies • Dependencies can be stored in private and final ﬁelds • Dagger must create the object

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Constructor Injection • @Inject on a single constructor • All constructor arguments are dependencies • Dependencies can be stored in private and final ﬁelds • Dagger must create the object • @Provides not required for downstream injection

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Field Injection

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Field Injection • @Inject on ﬁelds which are dependencies

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Field Injection • @Inject on ﬁelds which are dependencies • Field may not be private or final

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public class TweeterApp { @Inject Tweeter tweeter; @Inject Timeline timeline; // ... }

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public class TweeterActivity extends Activity { @Inject Tweeter tweeter; @Inject Timeline timeline; // ... }

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Field Injection • @Inject on ﬁelds which are dependencies • Field may not be private or final

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Field Injection • @Inject on ﬁelds which are dependencies • Field may not be private or final • Injection happens after the object is “alive”

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Field Injection • @Inject on ﬁelds which are dependencies • Field may not be private or final • Injection happens after the object is “alive” • Object often must be responsible for injecting itself

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The ObjectGraph

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The ObjectGraph • Central module (dependency) manager

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The ObjectGraph • Central module (dependency) manager • Injector

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ObjectGraph og = ObjectGraph.create( new NetworkModule(), new TwitterModule("JakeWharton") );

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ObjectGraph og = ObjectGraph.create( new NetworkModule(), new TwitterModule("JakeWharton") ); // Using constructor injection: TweeterApp app = og.get(TweeterApp.class);

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ObjectGraph og = ObjectGraph.create( new NetworkModule(), new TwitterModule("JakeWharton") ); // Using constructor injection: TweeterApp app = og.get(TweeterApp.class); // Using field injection: TweeterApp app = new TweeterApp(); og.inject(app);

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The ObjectGraph • Central module (dependency) manager • Injector

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The ObjectGraph • Central module (dependency) manager • Injector • Can be extended to create “scopes”

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ObjectGraph og = ObjectGraph.create( new NetworkModule(), new TwitterModule("JakeWharton") );

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ObjectGraph og = ObjectGraph.create( new NetworkModule() );

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ObjectGraph og = ObjectGraph.create( new NetworkModule(), new PersistenceModule(), new AccountModule() );

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ObjectGraph og = ObjectGraph.create( new NetworkModule(), new PersistenceModule(), new AccountModule() ); // Inject app things using ‘og’...

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ObjectGraph og = ObjectGraph.create( new NetworkModule(), new PersistenceModule(), new AccountModule() ); // Later... String user = "JakeWharton"; // Inject app things using ‘og’...

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ObjectGraph og = ObjectGraph.create( new NetworkModule(), new PersistenceModule(), new AccountModule() ); // Later... String user = "JakeWharton"; ObjectGraph userOg = og.plus(new TwitterModule(user)); // Inject app things using ‘og’... // Inject user things using ‘userOg’...

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OkHttpClient TwitterApi NetworkModule

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OkHttpClient TwitterApi NetworkModule PersistenceModule . . . AccountModule . . .

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OkHttpClient TwitterApi NetworkModule PersistenceModule . . . AccountModule . . . og

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OkHttpClient TwitterApi NetworkModule PersistenceModule . . . AccountModule . . . UserModule Tweeter Timeline og

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OkHttpClient TwitterApi NetworkModule PersistenceModule . . . AccountModule . . . UserModule Tweeter Timeline og userOg

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OkHttpClient TwitterApi NetworkModule PersistenceModule . . . AccountModule . . . UserModule Tweeter Timeline og userOg

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OkHttpClient TwitterApi NetworkModule PersistenceModule . . . AccountModule . . . UserModule Tweeter Timeline og userOg

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Android

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Android • Entry objects are managed objects constructed by OS

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Android • Entry objects are managed objects constructed by OS • Multiple services, activities, etc. required shared state

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Android • Entry objects are managed objects constructed by OS • Multiple services, activities, etc. required shared state • Platform is very difﬁcult to test

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Android • Entry objects are managed objects constructed by OS • Multiple services, activities, etc. required shared state • Platform is very difﬁcult to test • Build system allows for dynamic flavors and build types

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The ObjectGraph • Central module (dependency) manager • Injector • Can be extended to create “scopes”

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The ObjectGraph • Central module (dependency) manager • Injector • Can be extended to create “scopes” • Eagerly or lazily created on the Application by convention

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public class ExampleApp extends Application { private ObjectGraph objectGraph; @Override public void onCreate() { super.onCreate(); objectGraph = ObjectGraph.create( new ExampleModule() ); } public ObjectGraph getObjectGraph() { return objectGraph; } }

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public class ExampleActivity extends Activity { @Inject Foo foo; @Inject Bar bar; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ExampleApp app = (ExampleApp) getApplication(); app.getObjectGraph().inject(this); // ... } }

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Listing Injection Points

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Listing Injection Points • All injection points must be listed on a module

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Listing Injection Points • All injection points must be listed on a module • Used for aggressive static analysis

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Listing Injection Points • All injection points must be listed on a module • Used for aggressive static analysis • Potentially not needed for full compilation...

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Listing Injection Points • All injection points must be listed on a module • Used for aggressive static analysis • Potentially not needed for full compilation... • ...but absolutely required for incremental compilation

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@Module public class ExampleModule { @Provides @Singleton Foo provideFoo() { return new Foo(); } @Provides @Singleton Bar provideBar() { return new Bar(); } }

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@Module( injects = { ExampleActivity.class } ) public class ExampleModule { @Provides @Singleton Foo provideFoo() { return new Foo(); } @Provides @Singleton Bar provideBar() { return new Bar(); } }

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Use in Android

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Use in Android • Root ObjectGraph on Application

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Use in Android • Root ObjectGraph on Application • Activities, services, fragments, views obtain and inject

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Use in Android • Root ObjectGraph on Application • Activities, services, fragments, views obtain and inject • Modules and their “injects” segment parts of your app

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Use in Android: .plus()

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Use in Android: .plus() • Extend the graph with additional modules

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Use in Android: .plus() • Extend the graph with additional modules • Allows creating “scopes” of dependencies

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public class TweeterApp extends Application { private ObjectGraph objectGraph; @Override public void onCreate() { super.onCreate(); objectGraph = ObjectGraph.create( new NetworkModule(), new PersistenceModule(), new AccountModule(), ); } public ObjectGraph getObjectGraph() { return objectGraph; } }

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public class LandingActivity extends Activity { @Inject UserManager userManager; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ExampleApp app = (ExampleApp) getApplication(); app.getObjectGraph().inject(this); if (userManager.hasUser()) { // Start TimelineActivity, finish, return... } // Show log in / sign up... } }

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public class TimelineActivity extends Activity { @Inject Timeline timeline; @Inject Tweeter tweeter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ExampleApp app = (ExampleApp) getApplication(); ObjectGraph og = app.getObjectGraph(); String user = og.get(UserManager.class).getUser(); // TODO if user == null, finish and start LandingActivity... og.plus(new TwitterModule(user)).inject(this); // Set up timeline and tweeter UI... } }

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Use in Android: .plus()

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Use in Android: .plus()

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Use in Android: .plus()

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Use in Android: .plus() Forgot Password

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@Module( injects = { SignUpView.class, ForgotPasswordView.class } ) public class SignUpModule { private final SignUpActivity signUpActivity; public SignUpModule(SignUpActivity signUpActivity) { this.signUpActivity = signUpActivity; } @Provides @Singleton ActionBar provideActionBar() { return signUpActivity.getActionBar(); } }

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public class SignUpActivity class Activity { private final ObjectGraph childOg; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ExampleApp app = (ExampleApp) getApplication(); ObjectGraph og = app.getObjectGraph(); childOg = og.plus(new SignUpModule(this)); // Content set up and injection... } }

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public class SignUpView class LinearLayout { @Inject ActionBar actionBar; public SignUpView(Context context, AttributeSet attrs) { super(context, attrs); // Note: Injection happens by parent activity. } @Override public void onAttachedToWindow() { super.onAttachedToWindow(); actionBar.setTitle(R.string.sign_up); } }

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Use in Android: overrides

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Use in Android: overrides • Modules whose dependencies override others

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Use in Android: overrides • Modules whose dependencies override others • Only apply in the same ObjectGraph

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Use in Android: overrides • Modules whose dependencies override others • Only apply in the same ObjectGraph • Useful for customizing flavors and testing

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public class MockTimeline extends Timeline { private final List tweets = new ArrayList<>(); @Inject MockTimeline() { tweets.add(new Tweet("MockUser", "Hello, mock data!"); } @Override public List get() { return tweets; } public void addTweet(Tweet tweet) { tweets.add(new Tweet("MockUser", tweet), 0); } @Override public void loadMore(int amount) {} }

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public class MockTweeter extends Tweeter { private final MockTimeline timeline; @Inject MockTweeter(MockTimeline timeline) { this.timeline = timeline; } @Override public void tweet(String tweet) { timeline.addTweet(tweet); } }

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@Module( overrides = true ) public class MockTwitterModule { @Provides @Singleton public Tweeter provideTweeter(MockTweeter mockTweeter) { return mockTweeter; } @Provides @Singleton public Timeline provideTimeline(MockTimeline mockTimeline) { return mockTimeline; } }

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ObjectGraph og = ObjectGraph.create( new NetworkModule(), new TwitterModule("JakeWharton"), new MockTwitterModule(), );

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Timeline timeline = /* injected */ Tweeter tweeter = /* injected */

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Timeline timeline = /* injected */ Tweeter tweeter = /* injected */ for (Tweet tweet : timeline.get()) { System.out.println(tweet); } // MockUser: Hello, mock data!

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Timeline timeline = /* injected */ Tweeter tweeter = /* injected */ tweeter.tweet("Showing off more mock data! #DV13 #Dagger"); for (Tweet tweet : timeline.get()) { System.out.println(tweet); } // MockUser: Hello, mock data!

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Timeline timeline = /* injected */ Tweeter tweeter = /* injected */ for (Tweet tweet : timeline.get()) { System.out.println(tweet); } // MockUser: Showing off more mock data! #DV13 #Dagger // MockUser: Hello, mock data! tweeter.tweet("Showing off more mock data! #DV13 #Dagger"); for (Tweet tweet : timeline.get()) { System.out.println(tweet); } // MockUser: Hello, mock data!

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Mock Mode

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Mock Mode • Modules which override all network-calling classes

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Mock Mode • Modules which override all network-calling classes • Alternate implementations of network-calling classes which emulate a remote server but in-memory

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Mock Mode • Modules which override all network-calling classes • Alternate implementations of network-calling classes which emulate a remote server but in-memory • Fake images and data included in debug builds

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// src/release/java final class Modules { static Object[] list() { return new Object[] { new WalletModule() }; } }

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// src/release/java final class Modules { static Object[] list() { return new Object[] { new WalletModule() }; } } // src/debug/java final class Modules { static Object[] list() { return new Object[] { new WalletModule(), new DebugWalletModule() }; } }

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public class WalletApp extends Application { private ObjectGraph objectGraph; @Override public void onCreate() { super.onCreate(); objectGraph = ObjectGraph.create(Modules.list()); } public ObjectGraph getObjectGraph() { return objectGraph; } }

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Debug Drawer

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Debug Drawer • Provides quick access to developer options and information

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Debug Drawer • Provides quick access to developer options and information • Completely hidden from normal UI

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Debug Drawer • Provides quick access to developer options and information • Completely hidden from normal UI • Contains controls for changing app behavior

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U+2020 Sample App

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U+2020 Sample App • Dagger • Retroﬁt • RxJava • Picasso • OkHttp • Butter Knife • Timber • Build Flavors

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U+2020 Sample App • Dagger • Retroﬁt • RxJava • Picasso • OkHttp • Butter Knife • Timber • Build Flavors http://github.com/JakeWharton/u2020/

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U+2020 Sample App • Dagger • Retroﬁt • RxJava • Picasso • OkHttp • Butter Knife • Timber • Build Flavors http://github.com/JakeWharton/u2020/ #Soon

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Dependency Injection

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Dependency Injection • Do NOT ignore the pattern

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Dependency Injection • Do NOT ignore the pattern • Do NOT make every class use the pattern

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Dependency Injection • Do NOT ignore the pattern • Do NOT make every class use the pattern • Do NOT store dependencies as static ﬁelds

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“Avoid Dependency Injection”

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“Avoid Dependency Injection” Using a dependency injection framework such as Guice or RoboGuice may be attractive because they can simplify the code you write and provide an adaptive environment that's useful for testing and other conﬁguration changes. However, these frameworks tend to perform a lot of process initialization by scanning your code for annotations, which can require signiﬁcant amounts of your code to be mapped into RAM even though you don't need it. d.android.com/training/articles/memory.html#DependencyInjection

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Dagger Performance

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Dagger Performance • Annotation processor generates code to fulﬁll dependencies

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Dagger Performance • Annotation processor generates code to fulﬁll dependencies • Happens automatically inside of javac

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Dagger Performance • Annotation processor generates code to fulﬁll dependencies • Happens automatically inside of javac • Zero reflection on methods or ﬁelds

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Dagger Performance • Annotation processor generates code to fulﬁll dependencies • Happens automatically inside of javac • Zero reflection on methods or ﬁelds • Debugger and developer friendly