Swift 错误：NSInternalInconsistencyException，'上传尝试在非主队列上执行！只在主队列上。

Question

我正在我的应用程序（使用 TwitterKit）上实现使用 Twitter 选项登录，但它在下面的函数上不断崩溃 - saveUserIntoFirebaseDatabase（将用户数据、图像上传到 Firebase 数据库时）。我不明白为什么下面的函数需要在主队列中？

用户数据被提取并保存到 Firebase Auth 部分，但是在尝试将用户数据保存到实时数据库和存储时似乎崩溃了？

fileprivate func saveUserIntoFirebaseDatabase() {

    guard let uid = Auth.auth().currentUser?.uid,
    let name = self.name,
    let username = self.username,
    let email = self.email,
    let profileImage = profileImage,
    let profileImageUploadData = UIImageJPEGRepresentation(profileImage, 0.3) else { Service.dismissHud(self.hud, text: "Error", detailText: "Failed to save user.", delay: 3); return }
    let filename = UUID().uuidString

    let storageRef = Storage.storage().reference().child("profile_images").child(filename)
    storageRef.putData(profileImageUploadData, metadata: nil, completion: { (metadata, err) in

        if let err = err {
            Service.dismissHud(self.hud, text: "Error", detailText: "Failed to save user with error: \(err)", delay: 3);
            return
        }

        // Firebase 5 Update: Must now retrieve downloadURL
        storageRef.downloadURL(completion: { (downloadURL, err) in
        guard let profileImageUrl = downloadURL?.absoluteString else { return }
        print("Successfully uploaded profile image into Firebase storage with URL:")

        let dictionaryValues = ["name": name,
                                "email": email,
                                "username": username,
                                "profileImageUrl": profileImageUrl]
        let values = [uid : dictionaryValues]

        Database.database().reference().child("users").updateChildValues(values, withCompletionBlock: { (err, ref) in
            if let err = err {
                Service.dismissHud(self.hud, text: "Error", detailText: "Failed to save user info with error: \(err)", delay: 3)
                return
            }
            print("Successfully saved user info into Firebase database")
            // after successfull save dismiss the welcome view controller
            self.hud.dismiss(animated: true)
            self.dismiss(animated: true, completion: nil)
            })
        })
    })
} 

我设置的 MainTabBarController 有以下内容来查看当前用户是否已登录，如果没有，他们将被重定向到 Welcome Controller。会不会是这个原因？

fileprivate func checkLoggedInUserStatus() {
    if Auth.auth().currentUser == nil {
        DispatchQueue.main.async {
            let welcomeController = WelcomeController()
            let welcomeNavigationController = UINavigationController(rootViewController: welcomeController)
            self.present(welcomeNavigationController, animated: false, completion: nil)
            return
        }
    }
}

Answer 1

我认为您正试图在后台线程上关闭视图控制器。