[Kotlin] 코루틴 How to return value from async coroutine scope such as ViewModelScope to your UI?

https://stackoverflow.com/questions/60910978/how-to-return-value-from-async-coroutine-scope-such-as-viewmodelscope-to-your-ui

How to return value from async coroutine scope such as ViewModelScope to your UI?

 

Another way without using LiveData would be like this,

Similar to viewModelScope there is also a lifecycleScope available with lifecycle-aware components, which can be used from the UI layer. Following is the example,

Fragment

override fun onActivityCreated(savedInstanceState: Bundle?) {
    super.onActivityCreated(savedInstanceState)
    findByID.setOnClickListener {
        lifecycleScope.launch{
            val res = usermodel.findbyID(et2.text.toString().toInt())
            // use returned value to do anything.
        }
    }
}

ViewModel

//1st option
// make the function suspendable itself.use aync instead of launch and then
// use await to collect the returned value.
suspend fun findbyID(id: Int): userEntity  {
    val job = viewModelScope.async {
       val returnedrepo = repo.delete(id)
       Log.e(TAG,returnedrepo.toString())
       return@async returnedrepo
    }
    return job.await()
}

//2nd option
// make the function suspendable itself. but switch the execution on IO
// thread.(since you are making a DB call)
suspend fun findbyID(id: Int): userEntity  {
    return withContext(Dispatchers.IO){
       val returnedrepo = repo.delete(id)
       Log.e(TAG,returnedrepo.toString())
       return@withContext returnedrepo
    }
}

Since LiveData is specific to Android Environment, Using Kotlin Flow becomes a better option in some places, which offers similar functionality.