Example: RxSwift + RxCocoa

Sample.swift

//
//  ViewController.swift
//  RxSwiftExample
//
//  Created by Eunyeong Kim on 2020/05/27.
//  Copyright © 2020 Eunyeong Kim. All rights reserved.
//

import UIKit
import RxSwift
import RxCocoa

struct Weather {
    let cityName: String
    let temperature: Double
    let humidy: Double
}

struct APIClient {
    static let shared = APIClient()

    func requestWeather(city: String) -> Observable<Weather> {
        Observable.just(
            Weather(cityName: city,
                    temperature: 20,
                    humidy: 90)
        )
    }
}

final class ViewController: UIViewController {

    @IBOutlet private weak var tempLabel: UILabel!
    @IBOutlet private weak var humidityLabel: UILabel!
    @IBOutlet private weak var cityNameLabel: UILabel!

    @IBOutlet private weak var cityNameTextField: UITextField!

    private let indicatorView = UIActivityIndicatorView()

    private let disposeBag = DisposeBag()

    override func viewDidLoad() {
        super.viewDidLoad()

        let weather = cityNameTextField.rx.controlEvent(.editingDidEndOnExit)
            .asObservable()
            .map { [weak self] in self?.cityNameTextField.text }
            .filter { ($0 ?? "").count > 0 }
            .flatMapLatest { APIClient.shared.requestWeather(city: $0!) }

        setupBinding(weather: weather)
    }

}

private extension ViewController {

    func setupBinding(weather: Observable<Weather>) {
        let isIndicatorViewAnimating = Observable.from(
            [cityNameTextField.rx.text.map { _ in true },
             weather.map { _ in false }.asObservable()]
        ).merge()
            .startWith(true)
            .asDriver(onErrorJustReturn: false)

        isIndicatorViewAnimating
            .skip(1)
            .drive(indicatorView.rx.isAnimating)
            .disposed(by: disposeBag)

        [tempLabel, humidityLabel, cityNameLabel].forEach { view in
            isIndicatorViewAnimating
                .drive(view.rx.isHidden)
                .disposed(by: disposeBag)
        }

        weather
            .map { "\($0.temperature)도" }
            .bind(to: tempLabel.rx.text)
            .disposed(by: disposeBag)

        weather
            .map { "\($0.humidy)%" }
            .bind(to: humidityLabel.rx.text)
            .disposed(by: disposeBag)

        weather
            .map { "도시이름: \($0.cityName)" }
            .bind(to: cityNameLabel.rx.text)
            .disposed(by: disposeBag)
    }

}