class ViewController: ASViewController<ASScrollNode>, UIScrollViewDelegate {
  let someFixedNode: ASDisplayNode = {
    let node = ASDisplayNode()
    node.backgroundColor = .red
    node.style.height = ASDimension(unit: .points, value: 250)
    return node
  }()

  let someFlexibleNode: ASDisplayNode = {
    let node = ASDisplayNode()
    node.backgroundColor = .blue
    return node
  }()
  init() {
    super.init(node: ASScrollNode())
  }

  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  override func viewDidLoad() {
    super.viewDidLoad()
    self.node.view.alwaysBounceVertical = true
    self.node.view.showsVerticalScrollIndicator = false
    self.node.view.bounces = true
    self.node.automaticallyManagesSubnodes = true
    node.automaticallyManagesContentSize = true
    self.node.view.delegate = self
    self.node.setNeedsLayout()
    self.node.layoutSpecBlock = { node, sizeRange in
      return ASStackLayoutSpec(direction: .vertical,
                               spacing: 0,
                               justifyContent: .start,
                               alignItems: .stretch,
                               children: [self.someFlexibleNode, self.someFixedNode])

    }
  }
  // MARK: - UIScrollViewDelegate implementation
  func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if scrollView.contentOffset.y < 0 {
      someFlexibleNode.style.height = ASDimension(unit: .points, value: abs(scrollView.contentOffset.y))
      someFlexibleNode.setNeedsLayout()
    }
  }
}