如何在 Swift 中获取数据以从 NSURLSessionDataTask 返回

Question

我有同样的问题，在这里被问和回答：How to get data to return from NSURLSessionDataTask

区别：我如何在 Swift 中做到这一点？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..

因此，鉴于下面的代码，我有一个 FirstViewController，它将调用我的 HomeModel 类去使用 NSURLSession 调用获取数据。调用完成后，我想将数据返回给 FirstViewController，以便我可以在视图中进行设置。

FirstViewController 类看起来像：

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 传入完成处理程序的方法，或者使用类似于 C# 5 的方式使用异步任务来等待结果..

任何帮助表示赞赏..

Answer 1

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 ...
}

Answer 2

在来自 Abizern 的帮助和建议下，如果你愿意，我终于学会了如何编写这个块或闭包。

那么最后对我有用的是什么：

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
}

Answer 3

更改您的 GetHomeData() 方法，使其占用一个块。当您调用该方法时，将它传递给您想要对数据执行什么操作的块。在数据任务的完成块中，调用这个传入的块。