没有可可豆荚的未解决的标识符GGLContext

Question

我已按照Google的所有说明获取Google Sign-in SDK iOS（不CocoaPods），我尝试模拟应用程序，我就是这样收到此错误：使用未解析的标识符GGLContext 有什么帮助吗？

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)")
    return true
}