ObjectBox & RecyclerView - Filter & Sort

Question

When using LiveData for the RecyclerView with filters, the code looks usually like this:

ViewModel.kt

private val selectedCategory = MutableLiveData<Category>()
val channels: LiveData<List<Channel>>
...
init{
channels = Transformations.switchMap(selectedCategory){ category ->
            category?.let { repository.getChannelsByCategory(category) }
        }
}

fun filterByCategory(category: Category?){
        category?.let {
            selectedCategory.postValue(category)
        }
 }

But now, I started using ObjectBox and I stuck here with the ObjectBoxLiveData. The Transformations are not applicable here:

ViewModelObjectBox.kt

private val selectedCategory = MutableLiveData<Category>()
val channels: ObjectBoxLiveData<List<Channel>>
...
init{
channels = Transformations.switchMap(selectedCategory){ category ->
            category?.let { repository.getChannelsByCategory(category) } // This is not working.
        }
}

How to proceed here?

Answer 1

For the moment I solved this using the "MediatorLiveData". Here is an example:

class ChannelViewModel {
...
private val selectedCategory: MutableLiveData<Category> = MutableLiveData()
val channelData = MediatorLiveData<List<Channel>>()

 init{
      channelData.addSource(selectedCategory) {
      channelData.value = this.channelRepository.getChannelsByCategory(it)
 }

  fun filterByCategory(category: Category){
        selectedCategory.value = category
    }
...
}

If there is a better way, I'd love to see it.