RxSwiftとは？導入方法と使い方まとめ！ストリームを理解する

import SwiftUI

struct TestView: View {
@State    var check = true

var body: some View {
    Button(action: {
      check.toggle()
    }){
      Text(check ? "ON" : "OFF")
    }
}
} 

import UIKit

class ViewController: UIViewController {

  let button = UIButton()
    
    override func viewDidLoad() {
        super.viewDidLoad()

        let screenWidth = self.view.frame.width
        let screenHeight = self.view.frame.height
                  
        // 位置とサイズ
        button.frame = CGRect(x:screenWidth/4, y:screenHeight/2,
                      width:screenWidth/2, height:60)
        // タイトル
        button.setTitle("ボタン", for:UIControl.State.normal)
        
        // タップされたときの処理
        button.addTarget(self,
              action: #selector(ViewController.buttonTapped(sender:)),
              for: .touchUpInside)
        
        // Viewにボタンを追加
        self.view.addSubview(button)
    }

    @objc  func buttonTapped(sender : Any) {
        print("ボタンをタップされたよ")
    }
}

pod 'RxSwift'
pod 'RxCocoa'

$ pod install                
Analyzing dependencies
Downloading dependencies
Installing RxCocoa (6.5.0)
Installing RxRelay (6.5.0)
Installing RxSwift (6.5.0)
Generating Pods project
Integrating client project

let text = textField.rx.text
        
text.subscribe(onNext: { _ in 
        print("next")
    }, onError: { _ in
        print("error")
    }, onCompleted: { 
        print("completed")
    }).disposed(by: disposeBag)

import UIKit
import RxSwift
import RxCocoa

class ViewController: UIViewController {

    let disposeBag = DisposeBag()

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let label = UILabel()
        label.frame = CGRect(x:130, y:200,width:200, height:50)
        label.text = "placeholder..." // textField.text とBindingされるので表示されることはない
        self.view.addSubview(label)

        let textField = UITextField()
        textField.frame = CGRect(x:130, y:300,width:200, height:50)
        textField.borderStyle = UITextField.BorderStyle.line
        self.view.addSubview(textField)

        // Observableクラスの取得
        let text = textField.rx.text
        // ストリームの観測開始        
        text.subscribe(onNext: { [weak self] text in
                label.text = text // 変化した値をUIとリンク
            }, onError: { _ in
                print("error")
            }, onCompleted: {
                print("completed")
            }).disposed(by: disposeBag)
    }
}

rxプロパティ：Reactive<UITextField>を取得
textプロパティ：ControlProperty<<Optional<String>>を取得
subscribeメソッド：購読
disposed：観測終了用

override func viewDidLoad() {
  super.viewDidLoad()
  
  let label = UILabel()
  label.frame = CGRect(x:130, y:200,width:200, height:50)
  label.text = "placeholder..."
  self.view.addSubview(label)

  let textField = UITextField()
  textField.frame = CGRect(x:130, y:300,width:200, height:50)
  textField.borderStyle = UITextField.BorderStyle.line
  self.view.addSubview(textField)
  
  textField.rx.text.orEmpty
  .bind(to: label.rx.text)
  .disposed(by: disposeBag)
}

import UIKit
import RxSwift
import RxCocoa

class ViewController: UIViewController {

    let disposeBag = DisposeBag() 

    override func viewDidLoad() {
      super.viewDidLoad()
    
      let button = UIButton()
      button.frame = CGRect(x: 0, y:0, width: 100 , height: 40)
      button.setTitle("Tap!!", for: .normal)
      button.backgroundColor = UIColor.orange
      button.center = self.view.center
      self.view.addSubview(button)
      
      button.rx.tap
          .subscribe(onNext: { _ in
              print("tap")
          }, onError: { _ in
              print("error")
          }, onCompleted: {
              print("completed")
          }).disposed(by: disposeBag)
}

text.subscribe(onNext: { [weak self] text in
              label.text = text // 変化した値をUIとリンク
          }, onError: { _ in
              print("error")
          }, onCompleted: {
              print("completed")
          }).disposed(by: disposeBag)

let text = textField.rx.text
        
text.map{ [weak self] text -> String? in
  guard let text = text else { return nil }
  return "UITextFieldの値：\(text)"
}
.subscribe(onNext: { [weak self] text in
        label.text = text
    }, onError: { _ in
        print("error")
    }, onCompleted: {
        print("completed")
    }).disposed(by: disposeBag)

public func map<Result>(_ transform: @escaping (Element) throws -> Result)
    -> Observable<Result> {
    Map(source: self.asObservable(), transform: transform)
}

text.map{ [weak self] text -> String? in
  guard let text = text else { return nil }
  return "UITextFieldの値：\(text)"
}

text.filter{ $0!.count > 5 }
.subscribe(onNext: { text in
          label.text = text
      }, onError: { _ in
          print("error")
      }, onCompleted: {
          print("completed")
      }).disposed(by: disposeBag)