In Dagger 2 Dependency Injection...

What is the difference between @Provides, @Binds and @Inject ?

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[1] @Provides

Annotation for function creating the dependency. Can contain any arbitrary code, where you can define how the dependency should be created.

• ex: Create and inject Retrofit instance

@Module
class NetworkModule {
  @Provides
  fun provideRetrofit(baseUrl: String): Retrofit {
      return Retrofit.Builder()
          .baseUrl(baseUrl)
          .addConverterFactory(GsonConverterFactory.create())
          .build()
  }
  
  
  @Provides
  fun provideApiService(retrofit: Retrofit): ApiService {
      return retrofit.create(ApiService::class.java)
  }
}

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[2] @Binds

Just a shortcut used instead of @Provides when you want to bind an interface/abstract class to its implementation.

• It can take only a single parameter and the type return is the interface/class implemented by the given parameter object.

Note: You can’t use @Provides and @Binds methods together inn the same module class.

@Module
abstract class RepositoryModule {

  @Binds abstract fun bindRepository(repository: RemoteRepository): Repository

  @Binds abstract fun bindDataSource(dataSource: RemoteDataSource): DataSource
}

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[3] @Inject

Annotates the constructor of a class, if the constructor is public and all its parameters can be provided by Dagger.

class NetworkClient @Inject constructor(
    private val apiService: ApiService,
    private val networkInterceptor: NetworkInterceptor
) {
    
    fun makeRequest(request: Request) {
      // Make the network request using apiService and networkInterceptor objects
    }
}