rxandroid validation

mCompositeDisposable!!.add(Observable.combineLatest(
RxTextView.textChangeEvents(etEmail).map { it.text().toString() },
RxTextView.textChangeEvents(etPw).map { it.text().toString() },
BiFunction { email: String, pwd: String ->
!TextUtils.isEmpty(email) && android.util.Patterns.EMAIL_ADDRESS.matcher(email).matches() && !TextUtils.isEmpty(pwd)
}).subscribe { s -> btnLogin.isEnabled = s })