KVO의 사용, 실용 사례: 탐색 모음 배경색 점차적 변화

let disposeBag = DisposeBag()
     
@objc dynamic var message = "hangge.com"
     
override func viewDidLoad() {
   super.viewDidLoad()
       
   // （1 ）
   Observable.interval(1, scheduler: MainScheduler.instance)
      .subscribe(onNext: { [unowned self] _ in
         // 
         self.message.append("!")
   }).disposed(by: disposeBag)
         
   // message 
   _ = self.rx.observeWeakly(String.self, "message")
      .subscribe(onNext: { (value) in
         print(value ?? "")
      })
}

override func viewDidLoad() {
   super.viewDidLoad()
         
   // frame 
    _ = self.rx.observe(CGRect.self, "view.frame")
            .subscribe(onNext: { frame in
               print("---   ---")
               print(frame!)
               print("
")
            })
}

// kvo 
_ = self.tableView.rx.observe(CGPoint.self, "contentOffset")
            .subscribe(onNext: {[weak self] offset in
               var delta = offset!.y / CGFloat(64) + 1
               delta = CGFloat.maximum(delta, 0)
               self?.barImageView?.alpha = CGFloat.minimum(delta, 1)
         })

import UIKit
import RxSwift
import RxCocoa
 
class ViewController: UIViewController {
     
    var tableView:UITableView!
     
    //// 
    var barImageView:UIView?
     
    let disposeBag = DisposeBag()
     
    override func viewDidLoad() {
        super.viewDidLoad()
         
        // 
        self.navigationController?.navigationBar.barTintColor = .orange
         
        // 
        self.barImageView = self.navigationController?.navigationBar.subviews.first
         
        // 
        self.tableView = UITableView(frame: self.view.frame, style:.plain)
        // 
        self.tableView!.register(UITableViewCell.self, forCellReuseIdentifier: "Cell")
        self.view.addSubview(self.tableView!)
         
        // 
        let items = Observable.just(Array(0...100).map{ " \($0)"})
         
        // （  cellForRowAt  ）
        items.bind(to: tableView.rx.items) { (tableView, row, element) in
            let cell = tableView.dequeueReusableCell(withIdentifier: "Cell")!
            cell.textLabel?.text = "\(element)"
            return cell
        }
        .disposed(by: disposeBag)
         
        // kvo 
        _ = self.tableView.rx.observe(CGPoint.self, "contentOffset")
            .subscribe(onNext: {[weak self] offset in
                print(offset?.y ?? 0.0)

                var delta = offset!.y / CGFloat(64)
                delta = CGFloat.maximum(delta, 0)
                self?.barImageView?.alpha = CGFloat.minimum(delta, 1)
            })
    }
}