Databinding

Synchronization.kt

//primera opción extener una funcin sobre [BaseObservable] que emita una [ObservableProperty] que emite el cambio y lo notifica
// a los databinders para repintar
inline fun <Param> BaseObservable.bindingParam(initialValue: Param,
                                               crossinline afterChange: (Param) -> Unit): ReadWriteProperty<BaseObservable, Param> =
        object : ObservableProperty<Param>(initialValue) {

            override fun afterChange(property: KProperty<*>, oldValue: Param, newValue: Param) {
                if (oldValue != newValue) {
                    [email protected]()
                    afterChange(newValue)
                }
            }
        }

//la otra opción es crear una extensión sobre ObservableField para que emita un Observable de Rx al que nos
//podamos suscribir.
private inline fun <reified T : DataBindingObservable, R : Any?> T.observe(
        crossinline block: (T) -> R
): Observable<R> = create { subscriber ->
    object : android.databinding.Observable.OnPropertyChangedCallback() {
        override fun onPropertyChanged(observable: DataBindingObservable, id: Int) = try {
            subscriber.onNext(block(observable as T))
        } catch (e: Exception) {
            subscriber.onError(e)
        }
    }.let {
        subscriber.setCancellable { this.removeOnPropertyChangedCallback(it) }
        this.addOnPropertyChangedCallback(it)
    }
}

Usage.kt

class ViewModel: BaseObservable {
 
 val _name = ObservableField<String>("")
 val _lastName = ObservableField<String>("")
    
 var enabled: Boolean by bindingParam(false) {}
 
 Observable.combineLatest(_name.observe(),
                _lastName.observe(),
                BiFunction { name: String, lastName: String ->  
                           enabled = name.isNotBlank() && lastName.isNotBlank()
                           })
}