Scopes in Dagger 2

Question

I probably missed something, but I thought Scopes like @Singleton are used to define \"scoped lifecycles\".

I use Dagger 2 in an Android app (but I don\'t think the

Answer 1

You can do the following to define a real singleton for multiple components. I am assuming @ApplicationScoped and @ActivityScoped to be the different scopes.

@Module public class MailModule {
  @Provides @ApplicationScoped 
  public AccountManager providesAccountManager() {
    return new AccountManager();
  }

  @Provides @ApplicationScoped
  public MailProvider providesMailProvider(AccountManager accountManager) {
        return new MailProvider(accountManager);
  }
}

Then a MailComponent can be defined for the MailModule. The LoginComponent and MenuComponent can depend on the MailComponent.

@ApplicationScoped
@Component(modules = MailModule.class)
public interface MailComponent {
  MailProvider mailProvider();
  AccountManager accountManager();
}

@ActivityScoped
@Component(dependencies = MailComponent.class)
public interface LoginComponent {
  LoginPresenter presenter();
}

@ActivityScoped
@Component(dependencies = MailComponent.class)
public interface MenuComponent {
  MenuPresenter presenter();
}

The MailComponent can be initialized as shown below and can be used in MenuComponent and LoginComponent again shown below.

MailComponent mailComponent = DaggerMailComponent.builder().build();

DaggerMenuComponent.builder().mailComponent(mailComponent).build();

DaggerLoginComponent.builder().mailComponent(mailComponent).build()