Keyboard in RxCocoa

Question

I have some code like this:

let search = searchCityName.rx.text
        .filter { ($0 ?? "").count > 0 }
        .flatMapLatest { text in
            return ApiController.shared.currentWeather(city: text ?? "Error")
                .catchErrorJustReturn(ApiController.Weather.empty)
        }
        .observeOn(MainScheduler.instance)
    search.map { "\($0.temperature)° C" }
        .bind(to: tempLabel.rx.text)
        .disposed(by: bag)

I found that .bind(to:) operator make the keyboard dismissed every time user tap on Return Key button. So how can I keep the keyboard from being dismissed? Thanks