Question

在重新加载表视图之前，我想要完成这两个请求（表视图取决于它们）。

我尝试过如下，但它不起作用。

请求1完成，然后在请求2中完成所有操作之前重新加载表视图。

DispatchQueue.global(qos: DispatchQoS.QoSClass.default).async {
        //1. request 1:
        self.serverRequestAuth("/request1")
        //2. request 2:
        self.serverRequestAuth("/request2")
            DispatchQueue.main.async{
                //3. reload the table view
                self.tableView.reloadData()
            }
    }

我该怎么办？

提及： serverRequestAuth 包含服务器请求，解析json，解析其中的字典。

方法serverRequestAuth：

func serverRequestAuth(_ requestName: String){
    let requestNameEscaped = requestName.addingPercentEncoding(withAllowedCharacters: CharacterSet.urlQueryAllowed)!


    var request = NSMutableURLRequest()
    request = NSMutableURLRequest(url: URL(string: "\(self.view.getServerPath())\(requestNameEscaped)")!, cachePolicy: NSURLRequest.CachePolicy.reloadIgnoringLocalCacheData, timeoutInterval: 5)

    request.httpMethod = "GET"
    request.setValue(self.view.getAuth(), forHTTPHeaderField: "Authorization")
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")

    let task = URLSession.shared.dataTask(with: request as URLRequest) {data, response, err in
        if data != nil {
            if let dictionary = self.parseJSONData(data!) {
                self.parseDictionary(dictionary, typeOfRequest: requestName)
            }
        }
    }
    task.resume()
}

Answer 1

尝试使用DispatchSemaphore

func serverRequestAuth(_ requestName: String){
    let requestNameEscaped = requestName.addingPercentEncoding(withAllowedCharacters: CharacterSet.urlQueryAllowed)!

    let semaphore = DispatchSemaphore(value: 0);
    var request = NSMutableURLRequest()
    request = NSMutableURLRequest(url: URL(string: "\(self.view.getServerPath())\(requestNameEscaped)")!, cachePolicy: NSURLRequest.CachePolicy.reloadIgnoringLocalCacheData, timeoutInterval: 5)

    request.httpMethod = "GET"
    request.setValue(self.view.getAuth(), forHTTPHeaderField: "Authorization")
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")

    let task = URLSession.shared.dataTask(with: request as URLRequest) {data, response, err in
        if data != nil {
            if let dictionary = self.parseJSONData(data!) {
                self.parseDictionary(dictionary, typeOfRequest: requestName)
                semaphore.signal();
            }
        }
    }
    task.resume()
    semaphore.wait(timeout: .distantFuture)
}

Answer 2

试试这个：

function moveOperationalToTop() {
  var specialId = "divOperationalDetails";
  var $main = $("#divMain");
  var $divs = $main.find('div');
  $main.empty();
  $divs.each(function() {
    if (this.id == specialId) $main.append($(this));
  });
  $divs.each(function() {
    if (this.id != specialId) $main.append($(this));
  });
}

你可以用：

来调用它

#divOperationalDetails {
  color: red
}

Answer 3

我曾经遇到过类似的问题。为了提供一个简单的解决方案，我编写了这个小型库：

https://github.com/prine/ROConcurrency

您可以在“任务”中对请求进行分组，并等待所有请求完成，然后重新加载表格。

var taskRequest1 = TaskComplex { (finished) -> () in
    self.serverRequestAuth("/request1", finished)
}

var taskRequest2 = TaskComplex { (finished) -> () in
    self.serverRequestAuth("/request2", finished)
}

var reloadTable = TaskComplex { (finished) -> () in
    DispatchQueue.main.async{
         // 3. reload the table view
         self.tableView.reloadData()
         finished()
    }
}

var barrierComplex = BarrierComplex(tasks: [taskRequest1, taskRequest2], afterTask: reloadTable)
barrierComplex.startTasks()

您的serverRequestAuth方法需要告诉它何时异步完成，因此您需要添加完成的回调：

func serverRequestAuth(_ requestName: String, _ finished:(Bool) -> ()) {
    let requestNameEscaped = requestName.addingPercentEncoding(withAllowedCharacters: CharacterSet.urlQueryAllowed)!


    var request = NSMutableURLRequest()
    request = NSMutableURLRequest(url: URL(string: "\(self.view.getServerPath())\(requestNameEscaped)")!, cachePolicy: NSURLRequest.CachePolicy.reloadIgnoringLocalCacheData, timeoutInterval: 5)

    request.httpMethod = "GET"
    request.setValue(self.view.getAuth(), forHTTPHeaderField: "Authorization")
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")

    let task = URLSession.shared.dataTask(with: request as URLRequest) {data, response, err in
        if data != nil {
            if let dictionary = self.parseJSONData(data!) {
                self.parseDictionary(dictionary, typeOfRequest: requestName)

                // Here you call finished to tell the Barrier that its finished
                finished()
            }
        }
    }
    task.resume()
}

在重新加载表视图

3 个答案: