Hi, am new to coroutines and flows and facing an i...

# coroutines

[Koya Sivaji]

Hi, am new to coroutines and flows and facing an issue with usage of Flows. Below is the code

DeviceDao{
@Query("SELECT * FROM devices")
    abstract fun getAllDevices(): Flow<List<Device>>
}

Repository layer

fun getAllDevices() = database.deviceDao().getAllDevices()

This repository method called form view model as below and every thing works fine

viewModelScope.launch {
            homes = homeRepository.homes.asLiveData()
            devices = deviceRepository.getAllDevices().asLiveData()
        }

Issue I am facing:

Added another method at repository layer like below

private suspend fun deleteDevicesNotInLambdaResponse(deviceJsonList: List<Device>) {

    var localDevices = emptyList<Device>()
    database.deviceDao().getAllDevices().collect {
        localDevices = it
      }


//. the below code never executes

        val localDeviceIds = localDevices.map { it.deviceId }
        val remoteDeviceIds = deviceJsonList.map { it.deviceId }

        val localDevicesNotInLambdaResponse = localDeviceIds.filterNot {     remoteDeviceIds.contains(it) }
        database.deviceDao().deleteDevices(localDevicesNotInLambdaResponse)
    
}

Basically, here I want to get all local devices and find out which are not in API response and delete those devices from local data base

As commented above, the code below the comment the below code never executes got never executed.

Looks like I am missing some thing about how the Flow operator works

Please suggest me how to fix this issue

[octylFractal]

I suspect that getAllDevices() never finishes for some reason, you'd have to consult whatever implements that

[okarm]

val localDevices = database.deviceDao().getAllDevices().first() will help you.

Alternatively add a suspend method to your Dao, which just returns List<Device>

This question would be better off in #android

[okarm]

On a philosophical note, you should really clean up your function and parameter and variable names.

[Koya Sivaji]

Thanks @okarm, database.deviceDao().getAllDevices().first() is working. Yes, @octylFractal flow never terminated when I call

database.deviceDao().getAllDevices().collect {
        localDevices = it
      }

Thank you guys for the help