VPVM Example of a ViewModel which can be used inside a ThirtyInch TiPresenter. This is built with Kotlin and Rx. While you may not use those technologies in your app you get the idea

ViewModelExample.kt

private class ViewModel {

    private var changing = PublishSubject.create<Unit>()

    fun observe(): Observable<ViewModel> {
        return Observable.just(this).mergeWith(changing.map { this })
    }

    var results: List<SearchResult> by onChangeNotifySubject(emptyList(), changing,
            { p, o, newValue -> if (newValue.isEmpty()) selectedResult = null })

    var selectedResult: SearchResult? by onChangeNotifySubject(null, changing)

    var dialog: ErrorDialog? by onChangeNotifySubject(null, changing)

    var showGeoSearchError: Boolean = false

    fun bindToView(view: GeoSearchView) {
        view.showSearchResults(results, selectedResult)

        dialog?.let {
            view.showErrorDialog(it.id, it.error)
        } ?: run {
            view.closeErrorDialog()
        }

        view.showGeoSearchError(showGeoSearchError)
    }
}

/**
 * Returns a property delegate for a read/write property that emits `null` to the subject.
 * @param initialValue the initial value of the property.
 * @param subject `onNext(next)` will be called after the change
 * @param action invoked before the subject will be triggered
 */
fun <T> onChangeNotifySubject(
        initialValue: T,
        subject: Subject<Unit, Unit>,
        action: (property: KProperty<*>, oldValue: T, newValue: T) -> Unit = { p, o, n -> }): ReadWriteProperty<Any?, T> = object : ObservableProperty<T>(initialValue) {
        
    override fun afterChange(property: KProperty<*>, oldValue: T, newValue: T) {
        action(property, oldValue, newValue)
        // Yes, I haven't updated to RxJava 2
        subject.onNext(null)
    }
}