Get the value not the unit in try catch block in Kotlin using Android

Question

Android kotlin coroutine retrofit.

I want to get the value from the getPropeties to insert it in database. I Need a help for this? I need the value to be an instance of User not the unit value. My viewModel class is given below.

    import android.app.Application
    import android.content.Context
    import android.util.Log
    import androidx.lifecycle.LiveData
    import androidx.lifecycle.MutableLiveData
    import androidx.lifecycle.ViewModel
    import com.example.android.marsrealestate.database.AppDatabase
    import com.example.android.marsrealestate.database.User
    import com.example.android.marsrealestate.database.UserDao
    import com.example.android.marsrealestate.network.UsersApi
    import com.example.android.marsrealestate.network.UsersProperty
    import kotlinx.coroutines.*
    import retrofit2.Call
    import retrofit2.Callback
    import retrofit2.Response


    class OverviewViewModel(val database: UserDao,
                            application: Application): ViewModel() {
        private var viewModelJob = Job()
        private val coroutineScope = CoroutineScope(
                viewModelJob + Dispatchers.Main )
        private var user = MutableLiveData<User?>()
        // The internal MutableLiveData String that stores the most recent response
        private val _response = MutableLiveData<String>()

        // The external immutable LiveData for the response String
        val response: LiveData<String>
            get() = _response

        init {
            getUsersProperties()

        }

        private fun getUsersProperties(){
            coroutineScope.launch {
                var getPropertiesDeferred =
                        UsersApi.retrofitService.getProperties()
                try {
                    var listResult = getPropertiesDeferred.await()
                    //database.insertUser(listResult)
                    _response.value =
                            "Success: ${listResult} Mars properties retrieved"

                } catch (e: Exception) {
                    _response.value = "Failure: ${e.message}"
                }
            }
        }

        override fun onCleared() {
            super.onCleared()
            viewModelJob.cancel()
        }
    }

Thanks

Answer 1

You are using launch ,

Launch is used to perform asynchronous fire and forget type of operations where you are not interested in the result of operation.

Instead, you can use async ,

Async is used to perform asynchronous computation where you expect a result of the computation in the future

private fun getUsersProperties() =
            coroutineScope.async {
                var getPropertiesDeferred =
                        UsersApi.retrofitService.getProperties()
                try {
                    var listResult = getPropertiesDeferred.await()
                    //database.insertUser(listResult)
                    _response.value =
                            "Success: ${listResult} Mars properties retrieved"

                } catch (e: Exception) {
                    _response.value = "Failure: ${e.message}"
                }
              // =================================================
              // ========= Return whatever result you want =======
              // =================================================
            }

can you also show what is the type signature of getProperties ?