iOS UIScrollView不设置contentSize 自动布局自适应的方法

//创建UIScrollView
var scroView:UIScrollView= {

        let scroView =UIScrollView.init()

        scroView.backgroundColor = UIColor.green

        return scroView

    }()

//创建子view
var contentView: OrderDetailView = {
        let contentView = OrderDetailView.init(frame: CGRect.zero)
        return contentView
    }()

scroView.addSubview(contentView)//添加父容器

        contentView.snp.makeConstraints { (make) in
            make.left.equalToSuperview()
            make.right.equalToSuperview()
            make.top.right.equalToSuperview()
            make.size.equalTo(CGSize.init(width: ScreenW, height: ScreenH+50))
            make.bottom.equalToSuperview()
        }

重点是同时设置宽高和上下左右的约束
需要依赖自动布局框架
代码:swift <SnapKit>