savedstate.kt

internal fun <VM : ViewModel> viewModelFactory(
    create: () -> VM
): ViewModelProvider.Factory {
    return object : ViewModelProvider.Factory {
        @Suppress("UNCHECKED_CAST")
        override fun <VM : ViewModel> create(modelClass: Class<VM>): VM  = create() as VM
    }
}

internal fun <VM : ViewModel> Fragment.savedStateViewModelFactory(
    create: (savedStateHandle: SavedStateHandle) -> VM
): ViewModelProvider.Factory {
    return object : AbstractSavedStateViewModelFactory(this, arguments) {
        @Suppress("UNCHECKED_CAST")
        override fun <VM : ViewModel?> create(
            key: String, modelClass: Class<VM>, 
            handle: SavedStateHandle
        ): VM {
            return create(handle) as VM
        }
    }
}


// It will work with the default ViewModel delegates:

private val viewModel: FancyViewModel by viewModels {
    viewModelFactory {
        FancyViewModel()
    }
}

private val savedStateViewModel: FancySavedStateViewModel by viewModels {
    savedStateViewModelFactory { savedState ->            
        FancySavedStateViewModel(savedState)
    }
}