UIKit：从 AppDelegate 在视图控制器中运行函数

Question

我希望能够运行一个函数来告诉我应用程序何时从冷启动。我能够检测到应用程序何时来自冷启动，但我无法实际运行视图控制器中的功能，我什至希望在 viewdidAppear 之前运行它。

import UIKit
protocol AppLaunchDelegate: AnyObject {
   func appDidLaunchFromColdStart()
}
@UIApplicationMain
   class AppDelegate: UIResponder, UIApplicationDelegate {
   var window: UIWindow?
   weak var appLaunchDelegate: AppLaunchDelegate?
   func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    
    // Check if the app is launching from a cold start
    if launchOptions?[.source] == nil {
        // This is a cold start
        appLaunchDelegate?.appDidLaunchFromColdStart()
    }
    return true
    }
 }
class YourViewController: UIViewController, AppLaunchDelegate {
var didLaunchFromColdStart = false
override func viewDidLoad() {
    super.viewDidLoad()
    // Set the app delegate's delegate to self
    if let appDelegate = UIApplication.shared.delegate as? AppDelegate {
        appDelegate.appLaunchDelegate = self
    }
}
// Implement the delegate method
func appDidLaunchFromColdStart() {
    print("App launched from a cold start in the view controller")
    didLaunchFromColdStart = true
}
override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    
    if didLaunchFromColdStart {
        print("Code executed before viewDidAppear for a cold start")
        didLaunchFromColdStart = false
    }
  }
 }

Answer 1

这里的问题是应用程序委托无法访问视图控制器中事件的时间。好消息是，视图控制器显然可以访问其自身事件的时间。

同样，应用程序委托也无法神奇地看到视图控制器。但所有视图控制器都可以神奇地看到应用程序委托。

所以只要扭转你的沟通方向即可。将一个函数放入应用程序委托中，该函数知道这是否是冷启动，并让视图控制器从其任何标准事件实现中调用该函数（以最适合您的时间为准）。