class MyViewController: UIViewController {

    private var stackController = ScrollStackViewController()

    override func viewDidLoad() {
        super.viewDidLoad()
        
        stackController.view.frame = contentView.bounds
        contentView.addSubview(stackController.view)
    }
    
}

// Standard methods
let allRows = scrollStack.rows
let isEmpty = scrollStack.isEmpty // true if it does not contains row
let notHiddenRows = scrollStack.rows.filter { !$0.isHidden }

// By Visibility
let currentlyVisibleRows = scrollStack.visibleRows // only currently visible rows (partially or enterly)
let enterlyVisibleRows = scrollStack.enterlyVisibleRows // only enterly visible rows into the stack

// Shortcuts
let firstRow = scrollStack.firstRow
let lastRow = scrollStack.lastRow

   let welcomeVC = WelcomeVC.create()
   let tagsVC = TagsVC.create(delegate: self)
   let galleryVC = GalleryVC.create()
        
   stackView.addRows(controllers: [welcomeVC, notesVC, tagsVC, galleryVC], animated: false)

let newVC: UIViewController = ...
stackView.replaceRow(index: 1, withRow: newVC, animated: true) {
	print("Gallery controller is now in place!!")
}

let randomDst = Int.random(in: 1..<stackView.rows.count)
stackView.moveRow(index: 0, to: randomDst, animated: true, completion: nil)

stackView.setRowsHidden(indexes: [0,1,2], isHidden: true, animated: true)

public protocol ScrollStackRowAnimatable {
    /// Animation main info.
    var animationInfo: ScrollStackAnimationInfo { get }
    
    /// Animation will start to hide or show the row.
    func willBeginAnimationTransition(toHide: Bool)
    
    /// Animation to hide/show the row did end.
    func didEndAnimationTransition(toHide: Bool)
    
    /// Animation transition.
    func animateTransition(toHide: Bool)
}

extension WelcomeVC: ScrollStackRowAnimatable {
    public var animationInfo: ScrollStackAnimationInfo {
        return ScrollStackAnimationInfo(duration: 1, delay: 0, springDamping: 0.8)
    }

    public func animateTransition(toHide: Bool) {
        switch toHide {
            case true:
                self.view.transform = CGAffineTransform(translationX: -100, y: 0)
                self.view.alpha = 0
            
            case false:
                self.view.transform = .identity
                self.view.alpha = 1
        }
    }
    
    public func willBeginAnimationTransition(toHide: Bool) {
        if toHide == false {
            self.view.transform = CGAffineTransform(translationX: -100, y: 0)
            self.view.alpha = 0
        }
    }
    
}

class MyViewController: UIViewController {

	private let scrollStackController = ScrollStackController()
	
	@IBAction func someAction() {
		scrollStackController.scrollStack.reloadRow(0)
	}

}

// Your row 0 manages the GalleryVC, so in your GalleryVC implementation:

class GalleryVC: UIViewController, ScrollStackContainableController {

    public func func reloadContentFromStackView(stackView: ScrollStack, row: ScrollStackRow, animated: Bool) {
		// update your UI
	}
	
}

class GalleryVC: UIViewController, ScrollStackContainableController {

    public func scrollStackRowSizeForAxis(_ axis: NSLayoutConstraint.Axis, row: ScrollStackRow, in stackView: ScrollStack) -> ScrollStack.ControllerSize? {
    	switch axis {
    	case .horizontal:
       	  return .fixed(300)
      	case .vertical:
       	  return .fixed(500)
       }
    }
    
}

public func scrollStackRowSizeForAxis(_ axis: NSLayoutConstraint.Axis, row: ScrollStackRow, in stackView: ScrollStack) -> ScrollStack.ControllerSize? {
	return .fitLayoutForAxis
}

public class TagsVC: UIViewController, ScrollStackContainableController {

    public var isExpanded = false
    
    public func scrollStackRowSizeForAxis(_ axis: NSLayoutConstraint.Axis, row: ScrollStackRow, in stackView: ScrollStack) -> ScrollStack.ControllerSize? {
        return (isExpanded == false ? .fixed(170) : .fixed(170 + collectionView.contentSize.height + 20))
    }
}

	 // get the first row which manages this controller
	 let tagsRow = stackView.firstRowForControllerOfType(TagsVC.self)
	 // or if you have already the instance you can get the row directly
	 // let tagsRow = stackView.rowForController(tagsVCInstance)
	 
	 let tagsVCInstance = (tagsRow.controller as! TagsVC)
	 tagsVCInstance.isExpanded = !tagsVCInstance.isExpanded
	 
	 stackView.reloadRow(tagsRow, animated: true)

public class PricingVC: UIViewController, ScrollStackContainableController {
    
    public weak var delegate: PricingVCProtocol?
    
    @IBOutlet public var pricingTable: UITableView!
    @IBOutlet public var pricingTableHeightConstraint: NSLayoutConstraint!
    
    public func scrollStackRowSizeForAxis(_ axis: NSLayoutConstraint.Axis, row: ScrollStackRow, in stackView: ScrollStack) -> ScrollStack.ControllerSize? {
        return .fitLayoutForAxis
    }
    
    override public func updateViewConstraints() {
        pricingTableHeightConstraint.constant = pricingTable.contentSize.height // the size of the table as the size of its content
        view.height(constant: nil) // cancel any height constraint already in place in the view
        super.updateViewConstraints()
    }
}

let myCustomView = UIView(frame: .zero)
myCustomView.backgroundColor = .green
myCustomView.heightAnchor.constraint(equalToConstant: 300).isActive = true
stackView.addRow(view: myCustomView)

scrollStack.firstRow?.onTap = { row in
	// do something on tap
}

class GalleryVC: UIViewController, ScrollStackRowHighlightable {

    public var isHighlightable: Bool {
    	return true
    }
    
    func setIsHighlighted(_ isHighlighted: Bool) {
    	self.view.backgroundColor = (isHighlighted ? .red : .white)
    }

}

let tagsVC = scrollStack.firstRowForControllerOfType(TagsVC.self) // TagsVC instance

let row = scrollStack.rowForController(tagsVC) // ScrollStackRow

scrollStackView.onChangeRow = { (row, isRemoved) in
  if isRemoved {
    print("Row at index \(row.index) was removed"
  } else {
    print("A new row is added at index: \(row.index). It manages \(type(of: row.controller))")
  }
}

class ViewController: ScrollStackController, ScrollStackControllerDelegate {
	
  func viewDidLoad() {
    super.viewDidLoad()
    
    self.scrollStack.stackDelegate = self
  }
	
  func scrollStackDidScroll(_ stackView: ScrollStack, offset: CGPoint) {
    // stack did scroll
  }
    
  func scrollStackRowDidBecomeVisible(_ stackView: ScrollStack, row: ScrollStackRow, index: Int, state: ScrollStack.RowVisibility) {
    // Row did become partially or entirely visible.
  }
    
  func scrollStackRowDidBecomeHidden(_ stackView: ScrollStack, row: ScrollStackRow, index: Int, state: ScrollStack.RowVisibility) {
    // Row did become partially or entirely invisible.
  }

  func scrollStackDidUpdateLayout(_ stackView: ScrollStack) {
    // This function is called when layout is updated (added, removed, hide or show one or more rows).
  }

  func scrollStackContentSizeDidChange(_ stackView: ScrollStack, from oldValue: CGSize, to newValue: CGSize) {
    // This function is called when content size of the stack did change (remove/add, hide/show rows).
  }

}