swift - 如何在 Swift 中获取从 NSURLSessionDataTask 返回的数据

Question

我在这里提出和回答了同样的问题:How to get data to return from NSURLSessionDataTask

不同之处:我如何在 Swift 中执行此操作？我根本不知道 Objective C，所以试图解释这个答案对我来说有点徒劳..

鉴于下面的代码，我有一个 FirstViewController，它会调用我的 HomeModel 类来使用 NSURLSession 调用获取数据。调用完成后，我想将数据返回给 FirstViewController，以便我可以在 View 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()
}

我想我想要一种从原始 all 传递完成处理程序的方法，或者使用异步任务等待结果的类似于 C# 5 的东西..

感谢任何帮助..

Answer 1

在 Abizern 的帮助和建议下，我终于设法编写了这个 block 或闭包，如果你愿意的话。

那么最终对我有用的是:

我修改的GetHomeData函数如下:

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()
}

然后我这样调用函数:

/*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
}