waitUntilAllTask​​sAreFinished错误Swift

Question

按下Submit按钮时,我在loginViewController中调用了这个调用:

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

而我发送的checkLogin函数只执行:

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()
}

当成功调用checkLogin函数时:true它无法执行SegueWithIdentified函数..错误如下所示:

在声明失败 - [UIKeyboardTaskQueue waitUntilAllTask​​sAreFinished],2014年11月15日/SourceCache/UIKit_Sim/UIKit-3318.16.14/Keyboard/UIKeyboardTaskQueue.m:374 17:41:29.540 Wavesss [8462:846477]***终止应用程序由于未捕获的异常"NSInternalInconsistencyException",原因是:" - [UIKeyboardTaskQueue waitUntilAllTask​​sAreFinished]只能从主线程调用."

请帮助我,虽然我很难找到解决方案,看起来我不能在视图控制器之间传递,而url任务仍在其他线程上执行.先谢谢你们!

Answer 1

您的checkLogin函数正在另一个线程上调用,因此您需要切换回主线程才能调用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)
        }        
    }
}

备选:xCode 10.1 1/2019

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

Answer 2

使用Xcode 8.0和Swift 3,它已被修改为以下构造:

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