CompositeDisposable

gistfile1.txt

private val compositeDisposable = CompositeDisposable()
private val photoChangeState: Subject<Boolean> = PublishSubject.create()

private var isPhotoChanged: Boolean = false    
        set(value) {
            field = value
            photoChangeState.onNext(value)
        }
        
//---------
 
 compositeDisposable.add(Observable.combineLatest(
                    /**устанавливаем листенеры полей*/
                    surnameForm.getValidatingObservable(),
                    nameForm.getValidatingObservable(),
                    patronymicForm.getValidatingObservable(),
                    photoChangeState,
                    Function4<Boolean, Boolean, Boolean, Boolean, Boolean> { nameIsPass, surnameIsPass, patronymicIsPass, photoChanged ->
                        /**активируем кнопку, если поля ФИО нормальные и поменялось ФИО или фото*/
                        nameIsPass && surnameIsPass && patronymicIsPass &&
                                (surnameForm.text != data.user!!.surname.orEmpty()
                                        || nameForm.text != data.user!!.name.orEmpty()
                                        || patronymicForm.text != data.user!!.patronymic.orEmpty()
                                        || photoChanged)
                    }).subscribe { setSaveButtonState(it) })