你的应用程序应该处理facebook的and google链接，然后返回true，如果一个or另一个可以处理给定的链接。

func application(application: UIApplication, openURL url: NSURL, sourceApplication: String?, annotation: AnyObject) -> Bool {

        let googleDidHandle = GIDSignIn.sharedInstance().handleURL(url,
            sourceApplication: sourceApplication,
            annotation: annotation)

        let facebookDidHandle = FBSDKApplicationDelegate.sharedInstance().application(
            application,
            openURL: url,
            sourceApplication: sourceApplication,
            annotation: annotation)

        return googleDidHandle || facebookDidHandle
}

在didFinishLaunching中：

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

    var configureError: NSError?
    GGLContext.sharedInstance().configureWithError(&configureError)
    assert(configureError == nil, "Error configuring Google services: \(configureError)")

    GIDSignIn.sharedInstance().delegate = self

    return FBSDKApplicationDelegate.sharedInstance().application(application, didFinishLaunchingWithOptions: launchOptions)

}

在Swift 3中，需要这样做：
覆写并实作下一个方法：

func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any]) -> Bool {
    let sourceApplication =  options[UIApplicationOpenURLOptionsKey.sourceApplication] as? String
    let annotation = options[UIApplicationOpenURLOptionsKey.annotation]

    let googleHandler = GIDSignIn.sharedInstance().handle(
        url,
        sourceApplication: sourceApplication,
        annotation: annotation )

    let facebookHandler = FBSDKApplicationDelegate.sharedInstance().application (
        app,
        open: url,
        sourceApplication: sourceApplication,
        annotation: annotation )

    return googleHandler || facebookHandler
}

然后道：

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    PFFacebookUtils.initializeFacebook(applicationLaunchOptions: launchOptions)
    FBSDKApplicationDelegate.sharedInstance().application(application, didFinishLaunchingWithOptions: launchOptions)

    var configureError: NSError?
    GGLContext.sharedInstance().configureWithError(&configureError)
    assert(configureError == nil, "Error configuring Google services: \(String(describing: configureError))")

    return true
}

在Swift 5中，你可以这样做：

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

    FBSDKCoreKit.ApplicationDelegate.shared.application(application, didFinishLaunchingWithOptions: launchOptions)

    GIDSignIn.sharedInstance().clientID = "your_client_id"
    GIDSignIn.sharedInstance().delegate = self

    return true
}

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
    let handledFB = FBSDKCoreKit.ApplicationDelegate.shared.application(app, open: url, options: options)
    let handledGoogle = GIDSignIn.sharedInstance().handle(url)
    return handledFB || handledGoogle
}