Dagger for dummies

ABUSING
DEPENDENCY INJECTION
WITH DAGGER
FOR DUMMIES
Saúl Díaz (@sefford)
Freakend ‘15

new Flipper(new Gintonic(new Gin(new Alcohol())))
FlipperGintonic GinAlcohol

SHOULD I USE DI WITH MY
PERSONAL/PRO PROJECT?

Flipper
Gin
Alcohol
Gintonic
Tonic
Trolling
Code
Google
Engineer
Tears
Android

@Module(
includes = RosieModule.class,
addsTo = {AndroidModule.class,
DrinkModule.class,
CodingModule.class
}
injects = FlipperFragment.class,
complete = true,
)
public class FlipperModule {
@Provides
@Named(“Tuenti”)
public FlipperInterface provideFlipper(Gintonic drink,
Trolling trolling, Android android) {
return new FlipperImpl(drink, trolling,
android);
}
}

public class FlipperFragment extends Fragment {
ObjectGraph graph;
@Inject
FlipperInterface flipper;
@Override
public void onCreate(Bundle bundle) {
graph = ObjectGraph.create(new FlipperModule());
graph.inject(this);
FlipperInterface flipper2 = graph.get(Flipper.class);
}

IDSPISPOPD FOR SINGLETONS
@Singleton
● By definition, Singletons cannot be tested
● Provides same instance of class for Graph
● This instance is not static

Lazy<Flipper> lazyFlipper;
● Creates the instance on lazyFlipper.get()
● Returns always the same instance (d’oh)
● Always done in UIThread!
LAZY INITIALIZATIONS

PROVIDING INSTANCES
Provider<Flipper> flipperProvider;
● Can help building your own Flipper army
● Returns a different instance each time

@Module(
override = true;
injects = FlipperFragment.class,
complete = true,
)
public class FlipperTestModule {
@Provides
@Singleton
public FlipperInterface provideFlipper() {
return mock(FlipperInterface.class);
}
}
MOCKING INSTANCES

DYNAMIC (SCOPED) INJECTION
public ObjectGraph extend() {
return graph.plus(new ExtensionModule1(),
new ExtensionModule2());
}

STATIC INJECTION
● Reduce boilerplate and mantenibility by
annotating classes and constructions
● Compilation-validated graph

SCOPED INJECTION
● Using a SOLID approach, change
implementations on runtime
● Graph runtime, validated
● Risk of “BOOOOOOM”

CLASSIC EXAMPLE
@Module(injects = LoginActivity.class,
addsTo = AppModule.class)
// @author Antonio Leiva
public class LoginModule {
private LoginView view;
public LoginModule(LoginView view) {
this.view = view;
}
@Provides @Singleton public LoginView provideView() {
return view;
}
@Provides @Singleton
public LoginPresenter providePresenter(LoginView loginView,
LoginInteractor loginInteractor) {
return new LoginPresenterImpl(loginView, loginInteractor);
}
}

WHY STOPPING THERE?public class NoNfcModule() {
@Provides
public NfcInterfaceController provideNfcController() {
return new NullNfcController();
}
}
public class NfcModule() {
@Provides
public NfcInterfaceController provideNfcController(
NfcAdapter adapter) {
return new NfcController(adapter);
}
}

// This goes on Api15Module
@Provides
@Singleton
public StatusBarControllerInterface provideStatusBarControllerInterface() {
return new StatusBarAPI15Controller();
}
@Provides
@Singleton
}
@Provides
@Singleton
}

ONE MORE CUP OF ABUSEpublic class ActiveProfileModule() {
@Provides
public ProfilePresenterInterface provideProfilePres(...) {
return new
ActiveProfilePresenter(basePresenter,...);
}
}
public class RegularProfileModule() {
@Provides
public ProfilePresenterInterface provideProfilePres(...) {
return new
RegularProfilePresenter(basePresenter,...);
}
}

Dagger for dummies

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