Can't log any data from API call - kotlin

Question

I'm pretty new to kotlin, and I feel pretty much overwhelmed by it. I'd like to ask - how I can display any data from MutableLiveData? I've tried to Log it, but it doesn't seem to work. I've already added the internet permission to the manifest. Here's the code:
ApiServices
interface ApiServices {
#GET("/fixer/latest/")
fun getRatesData(
#Query("base") base: String,
#Query("apikey") apikey: String
): Call<CurrencyModel>
companion object {
private const val url = "https://api.apilayer.com/"
var apiServices: ApiServices? = null
fun getInstance(): ApiServices {
if (apiServices == null) {
val retrofit = Retrofit.Builder()
.baseUrl(url)
.addConverterFactory(GsonConverterFactory.create())
.build()
apiServices = retrofit.create(ApiServices::class.java)
}
return apiServices!!
}
}
}
Repository
class CurrencyRepository constructor(private val apiServices: ApiServices) {
fun getLatestRates() = apiServices.getRatesData("EUR", "API_KEY");
}
ViewModel
class CurrencyViewModel constructor(private val currencyRepository: CurrencyRepository) :
ViewModel() {
val currencyRatesList = MutableLiveData<CurrencyModel>()
val errorMessage = MutableLiveData<String>()
fun getLatestRates() {
val response = currencyRepository.getLatestRates();
response.enqueue(object : retrofit2.Callback<CurrencyModel> {
override fun onResponse(
call: retrofit2.Call<CurrencyModel>,
response: Response<CurrencyModel>
) {
currencyRatesList.postValue(response.body())
}
override fun onFailure(call: retrofit2.Call<CurrencyModel>, t: Throwable) {
errorMessage.postValue(t.message)
}
})
}
}
FactoryViewModel
class CurrencyViewModelFactory constructor(private val repository: CurrencyRepository) :
ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
return if (modelClass.isAssignableFrom(CurrencyViewModel::class.java)) {
CurrencyViewModel(this.repository) as T
}else{
throw IllegalArgumentException("Couldn't found ViewModel")
}
}
}
MainActivity
class MainActivity : AppCompatActivity() {
private val retrofitService = ApiServices.getInstance()
lateinit var viewModel: CurrencyViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
viewModel = ViewModelProvider(this, CurrencyViewModelFactory(CurrencyRepository(retrofitService)))
.get(CurrencyViewModel::class.java)
viewModel.currencyRatesList.observe(this, Observer {
Log.d(TAG, "onCreate: $it")
})
viewModel.errorMessage.observe(this, Observer {
viewModel.getLatestRates()
})
}
}

Answer 1

You never call viewModel.getLatestRates() in your onCreate() to fetch an initial value for your LiveData, so it never emits anything to observe. The only place you have called it is inside your error listener, which won't be called until a fetch returns an error.
Side note, I recommend naming the function "fetchLatestRates()". By convention, "get" implies that the function returns what it's getting immediately rather than passing it to a LiveData later when its ready.
And a tip. Instead of this:
class MainActivity : AppCompatActivity() {
lateinit var viewModel: CurrencyViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// ...
viewModel = ViewModelProvider(this, CurrencyViewModelFactory(CurrencyRepository(retrofitService)))
.get(CurrencyViewModel::class.java)
//...
}
}
You can do this for the same result:
class MainActivity : AppCompatActivity() {
val viewModel: CurrencyViewModel by viewModels(CurrencyViewModelFactory(CurrencyRepository(retrofitService)))
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// ...
}
}