[BLOG] Example of ViewModel implementation with ViewState and Interactions

SettingsViewModel.kt

class SettingsViewModel(
    settingsRepository: SettingsRepository
) : ViewModel() {

    private var currentViewState = ViewState(
        firstName = "",
        lastName = "",
        notificationsChecked = false,
        notificationsEnabled = false
    )

    private val _viewState = MutableLiveData<ViewState>()
    val viewState: LiveData<ViewState> = _viewState

    init {
        val settings = settingsRepository.settings

        submitViewState(
            ViewState(
                firstName = settings.firstName,
                lastName = settings.lastName,
                notificationsChecked = settings.notificationsChecked,
                notificationsEnabled = settings.notificationsChecked
            )
        )
    }

    private fun submitViewState(viewState: ViewState) {
        currentViewState = viewState
        _viewState.postValue(currentViewState)
    }

    fun onInteraction(interaction: Interaction) {
        when (interaction) {
            is NotificationSwitchChanged -> notificationsSwitchChanged(interaction.enabled)
            is FirstNameChange -> firstNameChanged(interaction.firstName)
            is LastNameChange -> lastNameChanged(interaction.lastName)
            is NotificationSettingButtonClick -> notificationsSettingsButtonClicked()
            is HelpButtonButtonClick -> helpButtonClicked()
            is LogOutButtonClick -> logOutButtonClicked()
            is AdvancedSettingsButtonClick -> advancedSettingsButtonClicked()
        }
    }

    private fun notificationsSwitchChanged(checked: Boolean) {
        submitViewState(
            currentViewState.copy(
                notificationsChecked = checked,
                notificationsEnabled = checked
            )
        )

        /* logic */
    }

    private fun firstNameChanged(name: String) {
        /* logic */
    }

    private fun lastNameChanged(name: String) {
        /* logic */
    }

    private fun notificationsSettingsButtonClicked() {
        /* logic */
    }

    private fun helpButtonClicked() {
        /* logic */
    }

    private fun logOutButtonClicked() {
        /* logic */
    }

    private fun advancedSettingsButtonClicked() {
        /* logic */
    }
}