CLE-Counter.playground

//: A UIKit based Playground for presenting user interface
  
import UIKit
import RxSwift
import RxCocoa
import PlaygroundSupport
import Cause_Logic_Effect

PlaygroundPage.current.liveView = CounterViewController().configure { $0.connect() }

final class CounterViewController: UIViewController {
    var decrementButton: UIButton!
    var countLabel: UILabel!
    var incrementButton: UIButton!
    let disposeBag = DisposeBag()
    
    override func loadView() {
        super.loadView()
        view.backgroundColor = .white
        decrementButton = UIButton(type: .system).setup {
            $0.setTitle("-", for: .normal)
        }
        countLabel = UILabel().setup {
            $0.font = .monospacedDigitSystemFont(ofSize: 17, weight: .medium)
        }
        incrementButton = UIButton(type: .system).setup {
            $0.setTitle("+", for: .normal)
        }
        let rootStackView = UIStackView(arrangedSubviews: [
            decrementButton,
            countLabel,
            incrementButton,
        ]).setup {
            $0.translatesAutoresizingMaskIntoConstraints = false
        }
        view.addSubview(rootStackView)
        NSLayoutConstraint.activate([
            rootStackView.centerXAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.centerXAnchor),
            rootStackView.centerYAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.centerYAnchor),
        ])
    }
}

extension CounterViewController {
    func connect() {
        CounterLogic.counter(
            increment: incrementButton.rx.tap.asObservable(),
            decrement: decrementButton.rx.tap.asObservable()
        )
            .bind(to: countLabel.rx.text)
            .disposed(by: disposeBag)
    }
}

enum CounterLogic {
    static func counter(increment: Observable<Void>, decrement: Observable<Void>) -> Observable<String> {
        Observable.merge(
            increment.map(to: 1),
            decrement.map(to: -1)
        )
            .scan(0) { $0 + $1 }
            .startWith(0)
            .map { "\($0)" }
    }
}