从ViewController中的AppDelegate访问变量

我正在我的应用上实施Google登录,我需要访问用户ID和名/姓.存储该数据的变量位于App Delegate中.我已经在内部和外部搜索了如何在Swift 3中执行此操作,并且绝对没有任何内容.

这是App代表(至少是重要的部分):

class AppDelegate: UIResponder, UIApplicationDelegate, GIDSignInDelegate {

var window: UIWindow?
var databaseRef: FIRDatabaseReference!

var userID = String()
var givenName = String()
var familyName = String()

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.

    // Use Firebase library to configure APIs
    FIRApp.configure()

    GIDSignIn.sharedInstance().clientID = FIRApp.defaultApp()?.options.clientID
    GIDSignIn.sharedInstance().delegate = self

    return true
}

func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any] = [:]) -> Bool {

    return GIDSignIn.sharedInstance().handle(url,
                                             sourceApplication: options[UIApplicationOpenURLOptionsKey.sourceApplication] as? String,
                                             annotation: options[UIApplicationOpenURLOptionsKey.annotation])
}

func sign(_ signIn: GIDSignIn!, didSignInFor user: GIDGoogleUser!, withError error: Error!) {

    if let error = error {
        print(error.localizedDescription)
        return
    }
    print("User signed into Google")

    let authentication = user.authentication
    let credential = FIRGoogleAuthProvider.credential(withIDToken: (authentication?.idToken)!,
                                                      accessToken: (authentication?.accessToken)!)

    FIRAuth.auth()?.signIn(with: credential) { (user, error) in
        print("User Signed Into Firebase")


        self.databaseRef = FIRDatabase.database().reference()

        self.databaseRef.child("user_profiles").child(user!.uid).observeSingleEvent(of: .value, with: { (snapshot) in

            let snapshot = snapshot.value as? NSDictionary

            if(snapshot == nil)
            {
                self.databaseRef.child("user_profiles").child(user!.uid).child("name").setValue(user?.displayName)
                self.databaseRef.child("user_profiles").child(user!.uid).child("email").setValue(user?.email)
            }


        })

    }

    userID = user.userID
    givenName = user.profile.givenName
    familyName = user.profile.familyName


    continueToWallet()
}

在View Controller中,我正在调用App委托并尝试接收数据,但它给出了一个错误说"实例成员'用户ID'不能用于'AppDelegate'类型"

class addToWalletController: UIViewController {

var ID = String()

let delegate = UIApplication.shared.delegate as! AppDelegate
let user = AppDelegate.userID
let firstName = AppDelegate.givenName
let lastName = AppDelegate.familyName

override func viewDidLoad() {
    super.viewDidLoad()
}

}

我也尝试在= AppDelegate.userID中使用委托切换AppDelegate,但它给了我同样的错误.这是怎么回事？

错误消息已告诉您property initializers run before 'self' is available.

也许你应该初始化它 viewDidLoad

let delegate = UIApplication.shared.delegate as! AppDelegate
var user: String?
var firstName: String?
var lastName: String?

override func viewDidLoad() {
    super.viewDidLoad()

    user = delegate.userID
    firstName = delegate.givenName
    lastName = delegate.familyName
}

AppDelegate是班级.你想要的AppDelegate是你的应用程序委托的实例.此外,您不能使用delegate您声明的常量来设置其他实例成员的值,因为它也是实例成员本身.

我想像这样实现一个函数AppDelegate:

static func shared() -> AppDelegate {
    return UIApplication.shared.delegate as! AppDelegate
}

然后我可以从其他地方调用它:

let firstName = AppDelegate.shared().givenName

另一种选择是使用delegate您定义的属性设置这些属性的值,但是稍后再执行viewDidLoad,例如Alvin的回答建议.