SwiftUI项目集成AdMob遇报错：如何解决委托与视图控制器问题？

问题描述 #

作为SwiftUI新手，开发首款游戏时参照旧视频集成AdMob，遇到两个问题：

1. 编译错误：方法未找到 #

错误代码片段：

func present() {
    guard let root = UIApplication.shared.firstKeyWindowRootViewController() else {return}
    guard let interstitial else {
        print("Not Ready! Loading now!") ; load() ; return
    }
}

错误信息：

Value of type 'UIApplication' has no member 'firstKeyWindowRootViewController'

2. Swift 6兼容性警告：Main Actor隔离问题 #

警告代码片段：

func load() {
    let request = Request()
    InterstitialAd.load(with: adUnitID, request: request){ [weak self] ad, error in
        if let error { print("Failed to load \(error)"); return}
        self?.interstitial = ad
        self?.interstitial?.fullScreenContentDelegate = self
        print("interstitial has loaded!!!")
    }
}

警告信息：

Main actor-isolated conformance of 'InterstitialAdManager' to 'FullScreenContentDelegate' cannot be used in nonisolated context; this is an error in the Swift 6 language mode

修复方案 #

解决编译错误：修正方法名拼写 #

问题出在UIApplication扩展的方法名拼写错误：扩展里定义的是firstKeyWindowRootViewContoller()（末尾少了一个r），但调用时写的是firstKeyWindowRootViewController()。

修正扩展方法名（推荐，符合标准拼写）：

private extension UIApplication {
    // 修正拼写为 firstKeyWindowRootViewController
    func firstKeyWindowRootViewController() -> UIViewController? {
        connectedScenes
            .compactMap { ($0 as? UIWindowScene)?.keyWindow}
            .first?
            .rootViewController
    }
}

同时，present()方法缺少展示广告的核心代码，补充完整：

func present() {
    guard let root = UIApplication.shared.firstKeyWindowRootViewController() else {return}
    guard let interstitial else {
        print("Not Ready! Loading now!") ; load() ; return
    }
    // 新增：展示 interstitial 广告
    interstitial.present(fromRootViewController: root)
}

解决Main Actor警告 #

FullScreenContentDelegate属于Main Actor隔离的协议，而InterstitialAd.load的回调运行在非Main Actor上下文，直接赋值代理会触发警告。有两种修复方式：

方式1：在回调中切换到Main Actor执行赋值

func load() {
    let request = Request()
    
    InterstitialAd.load(with: adUnitID, request: request){ [weak self] ad, error in
        if let error { 
            print("Failed to load \(error)")
            return
        }
        guard let self = self else { return }
        // 切换到Main Actor队列执行代理赋值
        Task { @MainActor in
            self.interstitial = ad
            self.interstitial?.fullScreenContentDelegate = self
            print("interstitial has loaded!!!")
        }
    }
}

方式2：给整个管理器类标记Main Actor

直接让InterstitialAdManager类所有代码都运行在Main Actor上，从根源避免上下文不匹配：

@MainActor
final class InterstitialAdManager:NSObject, ObservableObject, FullScreenContentDelegate {
    private let adUnitID = "ca-app-pub-3940256099942544/1033173712"
    private var interstitial: InterstitialAd?
    
    // ... 原有方法代码保持不变 ...
}

内容的提问来源于stack exchange，提问作者Jason W