设置分段控件的默认子表视图控制器

import UIKit

class ViewController: UIViewController {
    
    var segmentControl: UISegmentedControl!
    var childViewControllers: [UIViewController] = []
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建分段控件
        segmentControl = UISegmentedControl(items: ["Option 1", "Option 2", "Option 3"])
        segmentControl.frame = CGRect(x: 50, y: 100, width: 300, height: 30)
        segmentControl.selectedSegmentIndex = 0 // 设置默认选项为第一个选项
        segmentControl.addTarget(self, action: #selector(segmentValueChanged(_:)), for: .valueChanged)
        view.addSubview(segmentControl)
        
        // 创建子表视图控制器
        let childVC1 = UIViewController()
        childVC1.view.backgroundColor = .red
        let childVC2 = UIViewController()
        childVC2.view.backgroundColor = .green
        let childVC3 = UIViewController()
        childVC3.view.backgroundColor = .blue
        
        childViewControllers = [childVC1, childVC2, childVC3]
        
        // 设置默认子表视图控制器
        addChild(childVC1)
        view.addSubview(childVC1.view)
        childVC1.didMove(toParent: self)
    }
    
    @objc func segmentValueChanged(_ sender: UISegmentedControl) {
        // 切换子表视图控制器
        let selectedVC = childViewControllers[sender.selectedSegmentIndex]
        for childVC in childViewControllers {
            if childVC == selectedVC {
                addChild(childVC)
                view.addSubview(childVC.view)
                childVC.didMove(toParent: self)
            } else {
                childVC.willMove(toParent: nil)
                childVC.view.removeFromSuperview()
                childVC.removeFromParent()
            }
        }
    }
}