关于ScrollView上放置ScrollView的滑动问题

项目中需求：向上滑动上层的ScrollView时，底层ScrollView优先滑动，当底层ScrollView滑动到最大值时，上层ScrollView继续滑动，向下滑动时，上层ScrollView滑动到最小值时，底层ScrollView开始滑动

代码保存

func scrollViewDidScroll(_ scrollView: UIScrollView) {
        
        let vc = self.childVcs[currentVCIndex]
        
        if scrollView == vc.tableView {
            let vcY = vc.tableView?.contentOffset.y ?? 0
            let backY:Int = Int(backScrollView.contentOffset.y)
            let newY = scrollView.contentOffset.y
            print(newY)
            if scrollView == vc.tableView {
                if vcY >= 0 && backY != Int(headerHeight) { // 让底层ScrollView向上滑动
                    if ((backY - Int(headerHeight)) > 0) {
                        
                        backScrollView.contentOffset = CGPoint.init(x: 0, y: Int(headerHeight))
//                        return
                    } else {
                        backScrollView.contentOffset = CGPoint.init(x: 0, y: CGFloat(backY) + vcY)
                    }
                    vc.tableView?.contentOffset = CGPoint.init(x: 0, y: 0)
                    
                } else if backY <= Int(headerHeight) && newY < 0 && backY > 0 { // 让底层ScrollView向下滑动
                    
                    if backY < 0 {
                        backScrollView.contentOffset = CGPoint.init(x: 0, y: 0)
                    } else {
                        backScrollView.contentOffset = CGPoint.init(x: 0, y: CGFloat(backY) + vcY)
                    }
                    vc.tableView?.contentOffset = CGPoint.init(x: 0, y: 0)
                } else {
//                    return
                }
            }
        }
        
    }