如何修改现有的UIViewController以允许滚动？

import UIKit

class ScrollableViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 1. 添加UIScrollView
        let scrollView = UIScrollView(frame: view.bounds)
        view.addSubview(scrollView)
        
        // 2. 调整布局
        let contentView = UIView()
        scrollView.addSubview(contentView)
        
        // 添加视图元素到contentView中
        let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 50))
        label.text = "这是一个滚动视图示例"
        contentView.addSubview(label)
        
        // 调整contentView的大小
        contentView.frame = CGRect(x: 0, y: 0, width: view.bounds.width, height: 200)
        
        // 3. 设置滚动范围
        scrollView.contentSize = contentView.bounds.size
        
        // 4. 启用滚动
        scrollView.isScrollEnabled = true
    }
}