SwiftUI集成Azure AD B2C登录遇MSAL错误，求解决方案

一、解决MSAL错误（parentViewController has no window!） #

错误核心原因是控制器视图未关联到window时就触发了MSAL登录请求，具体问题点：

• 重写了UIKit用于创建视图的核心方法loadView，打乱了视图生命周期
• 在viewDidLoad中手动调用loadView，此时控制器尚未完成视图挂载，无有效window关联

修复步骤： #

1. 删除自定义的loadView方法，将登录逻辑移至viewDidAppear（此时视图已挂载到window，具备有效上下文）
2. 移除viewDidLoad内的loadView()调用

二、iOS15+替换根视图方案（替代废弃的windows） #

iOS15起UIApplication.shared.windows被废弃，需通过UIWindowScene获取活跃场景，再修改其根控制器：

if let scene = UIApplication.shared.connectedScenes.first as? UIWindowScene,
   let window = scene.windows.first(where: { $0.isKeyWindow }) {
    window.rootViewController = UIHostingController(rootView: MainContentView())
}

注：将登录后的目标视图命名为MainContentView，避免与原ContentView形成循环引用（原ContentView包含登录视图，登录成功需跳转至新主视图）

修改后的完整代码 #

1. LoginViewController #

class LoginViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // 移除手动调用的loadView()
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        startLoginFlow()
    }

    private func startLoginFlow() {
        do {
            let authority = try MSALB2CAuthority(url: URL(string: "https://Kauthority/b2c_1_susi")!)
            let pcaConfig = MSALPublicClientApplicationConfig(
                clientId: "MyClientID",
                redirectUri: nil,
                authority: authority
            )
            pcaConfig.knownAuthorities = [authority]
            let application = try MSALPublicClientApplication(configuration: pcaConfig)
            
            let webViewParameters = MSALWebviewParameters(authPresentationViewController: self)
            let interactiveParameters = MSALInteractiveTokenParameters(
                scopes: ["user.read"],
                webviewParameters: webViewParameters
            )

            application.acquireToken(with: interactiveParameters) { result, error in
                guard let result = result else {
                    print(error!)
                    return
                }

                if result.account.identifier != nil {
                    // iOS15+ 替换根视图
                    if let scene = UIApplication.shared.connectedScenes.first as? UIWindowScene,
                       let window = scene.windows.first(where: { $0.isKeyWindow }) {
                        window.rootViewController = UIHostingController(rootView: MainContentView())
                    }
                }
            }
        } catch {
            print(error)
        }
    }
}

2. 登录后主视图 #

struct MainContentView: View {
    var body: some View {
        Text("登录成功，欢迎进入主界面")
            .font(.largeTitle)
    }
}

3. 原ContentView与UIViewControllerRepresentable #

struct LoginUIViewRepresentable: UIViewControllerRepresentable {
    func makeUIViewController(context: Context) -> LoginViewController {
        LoginViewController()
    }

    func updateUIViewController(_: LoginViewController, context _: Context) {}
}

struct ContentView: View {
    var body: some View {
        LoginUIViewRepresentable()
    }
}

内容的提问来源于stack exchange，提问作者David Harinson