ios - PushViewController 在 httpPost 之后不起作用

Question

我制作了一个登录屏幕，它接受输入并与 REST api 通信以验证用户。如果响应为真，我将登录用户，否则不会。我写了一个方法 openViewControllerBasedOnIdentifier(id) 来切换 View 。

REST api 适本地返回 true 和 false。推送 Controller 被调用，但 View 没有改变。如果我在 LoginAction 方法 'self.openViewControllerBasedOnIdentifier("PlayVC")' 中只放置一行并删除其余代码，它会如何工作？

这是我的代码 @IBAction func LoginAction(_ sender: Any) {

    //self.openViewControllerBasedOnIdentifier("PlayVC")

Constants.login_status = false
    //created NSURL
    let requestURL = NSURL(string: URL_BK)

    //creating NSMutableURLRequest
    let request = NSMutableURLRequest(url: requestURL! as URL)

    //setting the method to post
    request.httpMethod = "POST"
    let username = phonenumber.text

    //creating the post parameter by concatenating the keys and values from text field
    let postParameters = "username="+username!+"&password=bk&schoolId=0";

    //adding the parameters to request body
    request.httpBody = postParameters.data(using: String.Encoding.utf8)


    //creating a task to send the post request
    let task = URLSession.shared.dataTask(with: request as URLRequest){
        data, response, error in
        let responseData = String(data: data!, encoding: String.Encoding.utf8)
        if error != nil{
            print("error is \(error)")
            return;
        }

        //parsing the response
        do {

            print(“Received data is ---%@",responseData as Any)

            let myJSON =  try JSONSerialization.jsonObject(with: data! , options: .allowFragments) as? NSDictionary


            if let parseJSON = myJSON {


                var status : Bool!

                status = parseJSON["status"] as! Bool?
                //print(status)

                if status==false
                {
                    Constants.login_status = false

                                        }
                else{
                    Constants.login_status = true
                    print("calling PLAYVC")

                    self.openViewControllerBasedOnIdentifier("PlayVC")


                }

            }
            else{
                print("NULL VALUE RECEIVED")
            }


        } catch {
            print(error)
        }

    }
    //executing the task
    task.resume()




}

Answer 1

你应该像这样在主线程上打开新的 View Controller :

DispatchQueue.main.async {
    self.openViewControllerBasedOnIdentifier("PlayVC")
}

当您调用 URLSession.shared.dataTask 时，您的 REST API 查询响应在后台线程中处理，因此当您调用任何 UI 操作时，您应该像上面那样包装代码以执行 UI 代码在主线程中。然后就可以正常工作了:)