Why are components and modules needed in Dagger…

Components and Modules in Dagger are the cornerstones of the dependency management framework in Android applications.

Modules:

They are classes annotated with @Module.
They are responsible for providing instances of objects, i.e., creating dependencies.
Methods inside a module annotated with @Provides tell Dagger how to create a specific type of object.
Modules group the logic of creating dependencies, making the code more organized and testable.

@Module
public class AppModule {

    @Provides // Tells Dagger how to create Context
    Context providesContext(Application application) {
        return application.getApplicationContext();
    }

    @Provides // Tells Dagger how to create SomeApi
    SomeApi providesSomeApi(Retrofit retrofit) {
        return retrofit.create(SomeApi.class);
    }
}

Components:

They are interfaces or abstract classes annotated with @Component.
They connect modules with classes where dependencies should be injected (e.g., Activities, Fragments, Services).
Components serve as "dependency graphs" that gather and provide dependencies from specified modules.
Methods in the component without parameters (injection methods) tell Dagger where to inject dependencies.
Methods in the component that return a type (provider methods) allow obtaining an instance of a dependency from the graph.
The @Component(modules = { ... }) annotation specifies which modules the component uses for providing dependencies.

@Component(modules = AppModule.class) // The component uses AppModule
public interface AppComponent {

    // Injection method: Dagger will inject dependencies into MainActivity
    void inject(MainActivity activity);

    // Provider method: allows obtaining an instance of SomeApi from the graph
    SomeApi someApi();
}

Relationship:

Components use modules to get instructions on how to create objects (dependencies).
Components then provide these created objects to classes that need them, through injection or provider methods.
This two-level structure (modules for creation, components for linking) allows efficient dependency management, making the code more modular, testable, and maintainable.

Thus, modules provide dependencies, and components connect these provided dependencies with the classes that use them.

Why are components and modules needed in Dagger?