dk_mvvm_6.kt

// before
class MainViewModel(val view: MainView) {

    private var currentItem: Item by Delegates.observable(Item.ITEM_A,
        { _: KProperty<*>, oldItem: Item, newItem: Item ->
            view.onUpdatedItem(oldItem, newItem)
        })

    fun onClicked(item: Item) {
        currentItem = item
    }
}

// after
class MainViewModel(val view: MainView, val dataStore: DataStore) {

    private var currentItem: Item by Delegates.observable(Item("kotlin", "#FF0000"),
        { _: KProperty<*>, oldItem: Item, newItem: Item ->
            view.onUpdatedItem(oldItem, newItem)
        })

    fun requestItemInfo(itemType: ItemType) {
        view.showProgress()
        try {
            currentItem = dataStore.getItemInfo(itemType)
        } catch (error: Throwable?) {
            view.onError(error)
        } finally {
            view.hideProgress()
        }
    }
}