Question

我遇到的问题与此处提出的问题相同：How to get data to return from NSURLSessionDataTask

区别：我怎样才能在Swift中做到这一点？我根本不了解Objective C所以试图解释这个答案对我来说有点徒劳......

因此，鉴于下面的代码，我有一个FirstViewController，它将调用我的HomeModel类来使用NSURLSession调用获取数据。一旦调用完成，我想将数据返回给FirstViewController，以便我可以在视图中设置它。

FirstViewController类如下所示：

import UIKit
class FirstViewController: UIViewController
{
    let homeModel = HomeModel()

    override func viewDidLoad()
    {
       super.viewDidLoad()

       // Go load the home page content
       SetHomeContent()
    }

  override func didReceiveMemoryWarning()
  {
      super.didReceiveMemoryWarning()
  }

  /*Call to go get home page content*/
  func SetHomeContent()
  {
      homeModel.GetHomeData();

      //TODO find a way to get result here... and set it to the textView
  }
}

HomeModel类看起来像：

 import Foundation
 class HomeModel
 {

    private let siteContent:String = "http://www.imoc.co.nz/MobileApp/HomeContent"

   func GetHomeData()
   {
      var url : NSURL! = NSURL(string:siteContent)
      var request: NSURLRequest = NSURLRequest(URL:url)
      let config = NSURLSessionConfiguration.defaultSessionConfiguration()
      let session = NSURLSession(configuration: config)

      let task : NSURLSessionDataTask = session.dataTaskWithRequest(request, completionHandler:      {(data, response, error) in

        var error: AutoreleasingUnsafeMutablePointer<NSError?> = nil

        let jsonResult: NSDictionary! = NSJSONSerialization.JSONObjectWithData(data, options: nil, error: error) as? NSDictionary!

      // At this stage I want the jsonResult to be returned to the FirstViewController
    });

    // do whatever you need with the task
    task.resume()
}

我想我想要一种方法来传递一个完成处理程序，从原来的所有或类似于C＃5的东西使用异步任务来等待结果..

任何帮助表示赞赏..

Answer 1

根据Abizern的帮助和建议，我终于知道了如果你想要的话如何编写这个块或闭包。

那么最终对我有用的是什么：

GetHomeData函数我改变如下：

private let siteContent:String = "http://www.imoc.co.nz/MobileApp/HomeContent"
// I changed the signiture from my original question
func GetHomeData(completionHandler: ((NSDictionary!) -> Void)?)
{
    var url : NSURL! = NSURL(string:siteContent)
    var request: NSURLRequest = NSURLRequest(URL:url)
    let config = NSURLSessionConfiguration.defaultSessionConfiguration()
    let session = NSURLSession(configuration: config)

    let task : NSURLSessionDataTask = session.dataTaskWithRequest(request, completionHandler: {(data, response, error) in
        var error: AutoreleasingUnsafeMutablePointer<NSError?> = nil

        let jsonResult: NSDictionary! =  NSJSONSerialization.JSONObjectWithData(data, options: nil, error: error) as? NSDictionary!

        // then on complete I call the completionHandler...
        completionHandler?(jsonResult?);
    });
    task.resume()
}

然后我调用这样的函数：

/*Call to go get home page content*/
func SetHomeContent()
{
    homeModel.GetHomeData(self.resultHandler)
}

func resultHandler(jsonResult:NSDictionary!)
{
    let siteContent = jsonResult.objectForKey("SiteContent") as NSDictionary
    let paraOne = siteContent.objectForKey("HomePageParagraphOne") as String
}

Answer 2

更改GetHomeData（）方法，使其占用一个块。当您调用该方法时，将传递给您执行数据所需的块。在数据任务的完成块中，调用此块传递。

Answer 3

您可以将此框架用于Swift协程-https://github.com/belozierov/SwiftCoroutine

DispatchQueue.main.startCoroutine {
    let dataFuture = URLSession.shared.dataTaskFuture(for: url)
    let data = try dataFuture.await().data
    . . . parse data ...
}

如何从Swift中的NSURLSessionDataTask返回数据

3 个答案: