iPhone 上的 UISplitViewController：从详细视图控制器弹出显示主视图

在iPhone上，使用UISplitViewController可以轻松实现主视图和详细视图的分割显示，这为我们开发复杂的界面提供了便利。然而，有时候我们可能需要在详细视图控制器中弹出或显示主视图控制器，以提供更好的用户体验。本文将介绍如何在iPhone上的UISplitViewController中实现这一功能，并通过一个案例代码来演示。

swift
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    let splitViewController = UISplitViewController()
    splitViewController.delegate = self
        
    let masterViewController = MasterViewController()
    let detailViewController = DetailViewController()
        
    splitViewController.viewControllers = [masterViewController, detailViewController]
        
    window = UIWindow(frame: UIScreen.main.bounds)
    window?.rootViewController = splitViewController
    window?.makeKeyAndVisible()
        
    return true
}

swift
class DetailViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let button = UIButton(type: .system)
        button.setTitle("Show Master", for: .normal)
        button.addTarget(self, action: #selector(showMaster), for: .touchUpInside)
        button.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(button)
        
        NSLayoutConstraint.activate([
            button.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            button.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        ])
    }
    
    @objc func showMaster() {
        if let splitViewController = splitViewController as? UISplitViewController {
            splitViewController.show(.primary)
        }
    }
}