CombineFrame.swift

private final class OfferingButton: UIViewController {

  @Published private var frame: CGRect = .zero

  private var subscriptions: [AnyCancellable] = []

  override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    $frame.removeDuplicates()
      .map { $0.height / 2 }
      .assign(to: \.cornerRadius, on: [outlineLayer, gradientLayer])
      .store(in: &subscriptions)
    $frame.removeDuplicates()
      .assign(to: \.frame, on: [outlineLayer, gradientLayer])
      .store(in: &subscriptions)

    control.publisher(for: .touchDown).sink { [unowned self] _ in
      self.animator.stopAnimation(true)
      self.view.transform = CGAffineTransform(scaleX: 0.9, y: 0.9)
    }.store(in: &subscriptions)

    control.publisher(for: [.touchUpInside, .touchCancel, .touchUpOutside]).sink { [unowned self] _ in
      self.animator.stopAnimation(true)
      self.animator = UIViewPropertyAnimator(duration: 0.3, dampingRatio: 0.8) {
        self.view.transform = .identity
      }
      self.animator.startAnimation()
    }.store(in: &subscriptions)
  }

  override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    self.frame = view.bounds
  }

  override func viewDidDisappear(_ animated: Bool) {
    super.viewDidDisappear(animated)
    subscriptions.cancelAll()
  }

  private lazy var outlineLayer: CALayer = {
    let layer = CALayer()
    layer.borderColor = Environment.swatch.yellowFill.cgColor
    layer.borderWidth = 2
    return layer
  }()

  private lazy var gradientLayer = Environment.swatch.yellowButtonGradient

}


extension Array where Element == AnyCancellable {
  func cancelAll() {
    for s in self { s.cancel() }
  }

  func store<C>(in collection: inout C) where C : RangeReplaceableCollection, C.Element == AnyCancellable {
    for s in self { s.store(in: &collection) }
  }
}

extension Publisher where Failure == Never {

  func assign<Root>(to keyPath: ReferenceWritableKeyPath<Root, Output>, on objects: [Root]) -> [AnyCancellable] {
    objects.map { root in
      assign(to: keyPath, on: root)
    }
  }
}