How to generate objects with the same type in Hilt?

Question

@Module
@InstallIn(SingletonComponent::class)
object NetworkModule {
    @Singleton
    @Provides
    fun provideRetrofit(okHttpClient: OkHttpClient): Retrofit {
        return Retrofit.Builder()
            .addConverterFactory(GsonConverterFactory.create())
            .baseUrl("http://example.com/")
            .client(okHttpClient)
            .build()
    }

    @Singleton
    @Provides
    fun provideMyRetrofit(okHttpClient: OkHttpClient): Retrofit {
        return Retrofit.Builder()
            .addConverterFactory(GsonConverterFactory.create())
            .baseUrl("http:/my.com/")
            .client(okHttpClient)
            .build()
    }
}

Their difference is only baseUrl.

---

I tried to solve this problem by use @Qualifier.

interface RetrofitQualifier {
    @Qualifier
    @Retention(AnnotationRetention.BINARY)
    annotation class Retrofit

    @Qualifier
    @Retention(AnnotationRetention.BINARY)
    annotation class MyRetrofit
}

@Module
@InstallIn(SingletonComponent::class)
object NetworkModule {

    @Singleton
    @Provides
    @RetrofitQualifier.Retrofit
    fun provideRetrofit(okHttpClient: OkHttpClient): Retrofit {
        return Retrofit.Builder()
            .addConverterFactory(GsonConverterFactory.create())
            .baseUrl("http://example.com/")
            .client(okHttpClient)
            .build()
    }

    @Singleton
    @Provides
    @RetrofitQualifier.MyRetrofit
    fun provideMyRetrofit(okHttpClient: OkHttpClient): Retrofit {
        return Retrofit.Builder()
            .addConverterFactory(GsonConverterFactory.create())
            .baseUrl("http:/my.com/")
            .client(okHttpClient)
            .build()
    }
}

---

And I use it by use @RetrofitQualifier.MyRetrofit in my class:

class MyRepository @Inject constructor(
    application: Application
)  {

    ...    

    @Inject
    @RetrofitQualifier.MyRetrofit
    lateinit var  retrofit:Retrofit


    private val service: Service = retrofit.create(Service::class.java)

    ...

    }

However, I was failed, the log is

kotlin.UninitializedPropertyAccessException: lateinit property retrofit has not been initialized

What should I do? Maybe use @Named? I am not sure...

Answer 1

Example with Qualifier, you can add this in the same file where you have your providers or even create a RetrofitQualifier.kt file and add them there.

@Qualifier
@Retention(AnnotationRetention.BINARY)
annotation class RetrofitOne

@Qualifier
@Retention(AnnotationRetention.BINARY)
annotation class RetrofitTwo

And the @Provides

@Singleton
@Provides
@RetrofitOne
fun provideRetrofit(okHttpClient: OkHttpClient): Retrofit {
    return Retrofit.Builder()
        .addConverterFactory(GsonConverterFactory.create())
        .baseUrl("http://example.com/")
        .client(okHttpClient)
        .build()
}

@Singleton
@Provides
@RetrofitTwo
fun provideMyRetrofit(okHttpClient: OkHttpClient): Retrofit {
    return Retrofit.Builder()
        .addConverterFactory(GsonConverterFactory.create())
        .baseUrl("http:/my.com/")
        .client(okHttpClient)
        .build()
}

Then in your Repository you can inject using two options

Field injection

// At field injection.
@AndroidEntryPoint
class MyRepository @Inject constructor(...) {

  @RetrofitOne
  @Inject lateinit var retrofit: Retrofit
}

As a dependency injected-constructor class

// As a dependency of a constructor-injected class.
class MyRepository @Inject constructor(
  @RetrofitTwo private val retrofit: Retrofit
) : ...

But the thing is that perhaps you installedIn in another module where your Repository doesn't have visibility.

About the @Named you can still use it but as per the documentation is recommended to use Qualifier