waitUntilAllTasksAreFinished error Swift

Question

按下提交按钮时，我的登录视图控制器中有此调用：

let http = HTTPHelper()
    http.post("http://someUrl.com/Login/userEmail/(username.text)/Pswd/(userPass.text)", postCompleted: self.checkLogin)

而我发送的 checkLogin 函数仅在执行：

func checkLogin(succeed: Bool, msg: String){
    if (succeed){
        self.performSegueWithIdentifier("logInTrue", sender: self)
    }
}

post函数是HTTPHelper类是：

func post(url : String, postCompleted : (succeeded: Bool, msg: String) -> ()) {
    var request = NSMutableURLRequest(URL: NSURL(string: url)!)
    var session = NSURLSession.sharedSession()
    request.HTTPMethod = "POST"
    var err: NSError?
     self.task = session.dataTaskWithURL(NSURL(string: url)!)  {(data, response, error) in
        var strData = NSString(data: data, encoding: NSUTF8StringEncoding)
        var err: NSError?
        var json = NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments, error: &err) as? NSDictionary
        var msg = "No message"
        // Did the JSONObjectWithData constructor return an error? If so, log the error to the console
        if(err != nil) {
            let jsonStr = NSString(data: data, encoding: NSUTF8StringEncoding)
            postCompleted(succeeded: false, msg: "Error")
        }
        else {
            // The JSONObjectWithData constructor didn't return an error. But, we should still
            // check and make sure that json has a value using optional binding.
            if let parseJSON = json {
                // Okay, the parsedJSON is here, let's get the value for 'success' out of it
                if let success = parseJSON["result"] as? Bool {
                    postCompleted(succeeded: success, msg: "Logged in.")
                }
                return
            }
            else {
                // Woa, okay the json object was nil, something went worng. Maybe the server isn't running?
                let jsonStr = NSString(data: data, encoding: NSUTF8StringEncoding)
                postCompleted(succeeded: false, msg: "Error")
            }
        }
    }
    self.task!.resume()
}

当 checkLogin 函数被成功调用时：true 它无法执行 SegueWithIdentification 函数。错误如下所示：

断言失败 in -[UIKeyboardTaskQueue

waitUntilAllTasksAreDone]，/SourceCache/UIKit_Sim/UIKit-3318.16.14/Keyboard/UIKeyboardTaskQueue.m：374 2014-11-15 17：41：29.540 Wavesss[8462：846477] *** 由于未捕获的异常"NSInternalInconsistencyException"而终止应用程序，原因："-[UIKeyboardTaskQueue waitUntilAllTasksAreDone]只能从主线程调用。

请帮助我，尽管我正在努力寻找解决方案，似乎当 url 任务仍在其他线程上执行时，我无法在视图控制器之间传递。提前感谢伙计们！

Answer 1

您的checkLogin函数正在另一个线程上调用，因此您需要先切换回主线程，然后才能调用self.performSegueWithIdentifier。我更喜欢使用NSOperationQueue：

func checkLogin(succeed: Bool, msg: String) {
    if (succeed) {
        NSOperationQueue.mainQueue().addOperationWithBlock {
            self.performSegueWithIdentifier("logInTrue", sender: self)
        }        
    }
}

替代： xCode 10.1 1/2019

func checkLogin(succeed: Bool, msg: String) {
    if (succeed) {
        OperationQueue.main.addOperation {
            self.performSegue(withIdentifier: "logInTrue", sender: self)
           }        
      }
 }

Answer 2

在 Xcode 8.0 和 Swift 3 中，这已被修改为以下结构：

OperationQueue.main.addOperation{
    <your segue or function call>
}

Answer 3

我也遇到了同样的问题，通过参考上面的答案得到了解决。谢谢@Nate

var storyBoard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
var vc: UINavigationController = storyBoard.instantiateViewControllerWithIdentifier("AppViewController") as! UINavigationController
NSOperationQueue.mainQueue().addOperationWithBlock {
    self.presentViewController(vc, animated: true, completion: nil)
}

Answer 4

尝试从异步任务内部更改文本框的内容时，我遇到了这个问题。

解决方案是使用 DispatchQueue（Xcode 8.0 和 Swift 3.0

）：

    DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
       self.textBox.text = "Some Value"
       }