Creating a component from multiple modules
suggest changeDagger 2 supports creating a component from multiple modules. You can create your component this way:
@Singleton @Component(modules = {GeneralPurposeModule.class, SpecificModule.class}) public interface MyMultipleModuleComponent { void inject(MyFragment myFragment); void inject(MyService myService); void inject(MyController myController); void inject(MyActivity myActivity); }
The two references modules GeneralPurposeModule
and SpecificModule
can then be implemented as follows:
GeneralPurposeModule.java
@Module public class GeneralPurposeModule { @Provides @Singleton public Retrofit getRetrofit(PropertiesReader propertiesReader, RetrofitHeaderInterceptor headerInterceptor){ // Logic here... return retrofit; } @Provides @Singleton public PropertiesReader getPropertiesReader(){ return new PropertiesReader(); } @Provides @Singleton public RetrofitHeaderInterceptor getRetrofitHeaderInterceptor(){ return new RetrofitHeaderInterceptor(); } }
SpecificModule.java
@Singleton @Module public class SpecificModule { @Provides @Singleton public RetrofitController getRetrofitController(Retrofit retrofit){ RetrofitController retrofitController = new RetrofitController(); retrofitController.setRetrofit(retrofit); return retrofitController; } @Provides @Singleton public MyService getMyService(RetrofitController retrofitController){ MyService myService = new MyService(); myService.setRetrofitController(retrofitController); return myService; } }
During the dependency injection phase, the component will take objects from both modules according to the needs.
This approach is very useful in terms of modularity. In the example, there is a general purpose module used to instantiate components such as the Retrofit
object (used to handle the network communication) and a PropertiesReader
(in charge of handling configuration files). There is also a specific module that handles the instantiation of specific controllers and service classes in relation to that specific application component.