UIScrollView nested scrolling solution

import Foundation


func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if scrollView == rootScrollView {
        if isParentViewCanScroll == false {
            rootScrollView.contentOffset.y = headerStickyHeight // point A
            isChildViewCanScroll = true
        } else if scrollView.contentOffset.y >= headerStickyHeight {
            rootScrollView.contentOffset.y = headerStickyHeight
            isParentViewCanScroll = false
            isChildViewCanScroll = true
        }
    } else {
        if isChildViewCanScroll == false {
            childScrollView.contentOffset.y = 0 // point B
        } else if scrollView.contentOffset.y <= 0 {
            isChildViewCanScroll = false
            isParentViewCanScroll = true
        }
    }