@IBOutlet weak var pageControl: HorizontalPageControlView!

override func viewDidLoad() {
    super.viewDidLoad()
    self.setPageControlTotalCount()
}

func setPageControlTotalCount() {

    // must set HorizontalPageControlView totalPageCount    
    self.pageControl.totalPageCount = 7
}

extension ViewController: UICollectionViewDelegate {
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
    
        // must set HorizontalPageControlView indicatorOffset    
        let offset = scrollView.contentOffset.x / scrollView.bounds.width
        self.pageControl?.indicatorOffset = offset
    }
}

// set SelectedColor in indicator
@IBInspectable var selectedColor: UIColor? {
    didSet { self.setNeedsDisplay() }
}

// set TotalCount
var totalPageCount: Int = 0 {
    didSet { self.setNeedsDisplay() }
}

// set Offset
var indicatorOffset: CGFloat = 0 {
    didSet { self.setNeedsDisplay() }
}

// usally get index in indicator
var selectedPosition: Int {
    get { return Int(round(self.indicatorOffset)) }
    set { self.indicatorOffset = CGFloat(newValue) }
}