Dependency injection with Koin

Question

I have a class that uses Dagger 2 for dependency injection. Now I want to switch to Koin for dependency injection. There are modules in Koin and I want to make a module out of the class or whatever can be done.

@Module
class NetModule(private val baseUrl: String) {

@Provides
@Singleton
fun providesOkHttpClient(
        httpLoggingInterceptor: HttpLoggingInterceptor): OkHttpClient = OkHttpClient.Builder().addInterceptor(
        httpLoggingInterceptor).build()

@Provides
@Singleton
fun provideLoggingInterceptor(): HttpLoggingInterceptor {
    val interceptor = HttpLoggingInterceptor(
            HttpLoggingInterceptor.Logger { message -> Logger.d("NETWORK: $message") })
    interceptor.level = HttpLoggingInterceptor.Level.NONE
    return interceptor
}

@Provides
@Singleton
fun providesMoshi(): Moshi = Moshi.Builder().add(KotlinJsonAdapterFactory()).build()

@Provides
@Singleton
fun providesRetrofit(okHttpClient: OkHttpClient, moshi: Moshi): Retrofit {
    return Builder().client(okHttpClient).baseUrl(baseUrl)
            .addConverterFactory(GsonConverterFactory.create())
            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
            .build()
}

@Provides
@Singleton
fun providesApiInterface(retrofit: Retrofit): ApiInterface = retrofit.create(
        ApiInterface::class.java)
}

Answer 1

Koin uses a DSL for describing modules. Usually you'd declare the module itself on a top-level. Since you need to provide baseUrl, you'd have to create a factory for it.

The @Provides annotation is completely irrelevant, but @Singleton needs to be translated and does so with single. To retrieve the dependencies, just call get().

fun netModule(baseUrl: String) = module {

    single {
        HttpLoggingInterceptor(
            HttpLoggingInterceptor.Logger { message ->
                Logger.d("NETWORK: $message")
        }).apply {
            level = HttpLoggingInterceptor.Level.NONE
        }
    }

    single {
        OkHttpClient.Builder()
            .addInterceptor(get<HttpLoggingInterceptor>())
            .build()
    }


    single {
        Moshi.Builder()
            .add(KotlinJsonAdapterFactory())
            .build()
    }

    single {
        Retrofit.Builder()
            .client(get())
            .baseUrl(baseUrl)
            .addConverterFactory(GsonConverterFactory.create())
            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
            .build()
    }

    single { get<Retrofit>().create(ApiInterface::class.java) }    
}