setupView.swift

func setupView(){
        view.backgroundColor = .black
        //setup the scrollView
        view.addSubview(parentScrollView)
        parentScrollView.fillSuperview()
        parentScrollView.contentSize = CGSize(width: DeviceSize.width,
                                              height: DeviceSize.height*2)

        //setup the content view
        parentScrollView.addSubview(contentView)
        contentView.anchorView(left: parentScrollView.leftAnchor,
                               width: parentScrollView.contentSize.width,
                               height: parentScrollView.contentSize.height)
        //setup content view top anchor
        contentViewTopAnchor = contentView.topAnchor.constraint(equalTo: parentScrollView.contentLayoutGuide.topAnchor, constant: 0)
        //activate it
        contentViewTopAnchor.isActive = true

        //setup the header view
        contentView.addSubview(headerView)
        headerView.anchorView(top: contentView.topAnchor,
                              left: contentView.leftAnchor,
                              right: contentView.rightAnchor)
        //setup header view height anchor
        headerViewHeightAnchor = headerView.heightAnchor.constraint(equalToConstant: 450)
        //activate it
        headerViewHeightAnchor.isActive = true

    }