Fetch data from Room with Flow

February 26, 2023

Hi guys I cannot fetch data from my database:

I have in my DAO:

   @Transaction
    @Query("SELECT * FROM ClientEntity")
    fun getClients(): Flow<List<ClientEntity>>

RepoImpl:

 override suspend fun getClients(): Flow<List<ClientEntity>> {
        return clientDao.getClients()
    }

ViewModel:

fun getClients(): Flow<List<Client>> = flow {
        val clients = mutableListOf<Client>()
        clientsRepository.getClients().collect { clientEntities ->
            clients.addAll(clientEntities.map { it.toClient() })
        }
        emit(clients)
    }

Screen:

LaunchedEffect(key1 = myContext) {  
            viewModel.getClients().collect{
                val clients = viewModel.getClients()
                Log.d(TAG, "ClientsListScreen: da $clients")
            }
        
    }

Im using jetpack compose, with this code I dont see logd in my Screen.
I know that are clients in my database since I inspected it.

>Solution :

First remove suspend keyword of getClients() from everywhere

You can also improve your View Model code like this

private val _clientResponse: MutableState<ClientState> = mutableStateOf(WeatherState())
    val clientResponse: State<ClientState> = _clientResponse


viewModelScope.launch {
                repository.getClients()
                    .onStart {
                         _clientResponse.value = ClientState(
                    isLoading =  true
                )
                    }.catch {
                         _clientResponse.value = ClientState(
                    error = it.message ?: "Something went wrong"
                )
                    }.collect{
                         _clientResponse.value = ClientState(
                    data = it
                )
                    }
            }


data class ClientState(
    val data: List< ClientEntity > = emptyList(),
    val error: String = "",
    val isLoading: Boolean = false
)

In Composable function

val clientResponse = viewModel.clientResponse.value

if (clientResponse.data.isNotEmpty())
 // do something

if (clientResponse.error.isNotEmpty)
// do something

if(clientResponse.isLoading)
// do something