How to use coroutines without runBlocking?-CodePudding

Using runBlocking I block main thread which is not proper. I would like to implement it more efficient.

    private fun getWorkItem(parentProjectId: Int?): WorkItemRoom? {
        val workItemRepository by inject<WorkItemRepository>()
        var returnParent: WorkItemRoom? = null
        runBlocking {
            if (parentProjectId != null) {
                returnParent = workItemRepository.getWorkItem(parentProjectId)
            }
        }
        return returnParent
    }

This is where I use it:

                val parentProject = getWorkItem(parentProjectId) ?: return@setOnMenuItemClickListener false

The entire code surrounding with navigation, showing button etc. which is related to this parentProject data.

    private fun updateMenuItems() {
        with(requireContext()) {
            val data = viewModel.data.value?.dataOrNull

            editMenuItem?.isVisible = hasInternetConnection() && (data?.isProjectEditable ?: false)
            editMenuItem?.setOnMenuItemClickListener {
                findNavController().navigate(
                    ProjectDetailsFragmentDirections.actionProjectDetailsFragmentToWorkItemFragment(
                        workItemType = WorkItemType.PROJECT,
                        workItemId = args.projectId,
                        requestKey = workItemRequestKey
                    )
                )
                true
            }

            goToParentMenuItem?.isVisible = data?.parentProjectId != null
            goToParentMenuItem?.setOnMenuItemClickListener {
                val parentProjectId = data?.parentProjectId ?: return@setOnMenuItemClickListener false
                val parentProject = getWorkItem(parentProjectId) ?: return@setOnMenuItemClickListener false

                findNavController().navigate(
                    ProjectDetailsFragmentDirections.actionProjectDetailsFragmentSelf(
                        projectId = parentProjectId,
                        isArchived = parentProject.workItemState.isClosed
                    )
                )
                true
            }
        }
    }

And finally this is my suspend function

class GetWorkItemByIdUseCase(private val workItemDao: WorkItemDao) :
    BaseUseCase<Int, WorkItemRoom>() {
    override suspend fun create(id: Int): WorkItemRoom = workItemDao.getWorkItemById(id)
}

How would you change it to get rid of runBlocking? I have tried some solutions, but what only worked is runBlocking. Basically I need to wait for returnParent value when I use it in next lines.

CodePudding user response：

This should work but the question/runBlocking suggests a deeper misunderstanding of how coroutines work. Coroutines are leveraging being highly reactive and not asynchronous.

goToParentMenuItem?.setOnMenuItemClickListener {
    lifecycleScope.launch {
        val parentProjectId = data?.parentProjectId ?: return@setOnMenuItemClickListener false
        val parentProject = getWorkItem(parentProjectId) ?: return@setOnMenuItemClickListener false

        findNavController().navigate(
            ProjectDetailsFragmentDirections.actionProjectDetailsFragmentSelf(
                    projectId = parentProjectId,
                    isArchived = parentProject.workItemState.isClosed
            )
        )
    }
    true
}

private suspend fun getWorkItem(parentProjectId: Int?): WorkItemRoom? = withContext(Dispatchers.IO) {
    val workItemRepository by inject<WorkItemRepository>()
    var returnParent: WorkItemRoom? = null
    if (parentProjectId != null) {
        workItemRepository.getWorkItem(parentProjectId)
    } else {
        null
    }
}

CodePudding user response：

You can implement the CoroutineScope interface and call launch to start a coroutine within methods of that class.

This official tutorial may help.

CodePudding user response：

I'd suggest simply marking getWorkingItem() with suspend, which will allow it to call other suspending functions without having to invoke a coroutine builder function. You can then use your ViewModel's scope to launch a coroutine to call getWorkingItem():

val parentProject = viewModelScope.async {
  getWorkItem(parentProjectId)
} 
if (parentProject.await() == null) return@setOnMenuItemClickListener false

EDIT: Added the await() call on parentProject.