从(_，_，_)类型的抛出函数-&gt；void到非抛出函数类型(NSData？，NSURLResponse？，NSError？)-&gt；void的转换无效

Invalid conversion from throwing function of type (_,_,_) throws -gt; Void to non-throwing function type (NSData?, NSURLResponse?, NSError?) -gt; Void(从(_，_，_)类型的抛出函数-gt；void到非抛出函数类型(NSData？，NSURLResponse？，NSError？)-gt；void的转换无效) - IT屋-程序员软件开发技术

问题描述

我已经编写了以下代码：

func getjson() {
        let urlPath = "https://api.whitehouse.gov/v1/petitions.json?limit=100"
        let url = NSURL(string: urlPath)
        let session = NSURLSession.sharedSession()
        let task = session.dataTaskWithURL(url!, completionHandler: {data, response, error -> Void in
            print("Task completed")
            if(error != nil) {
                print(error!.localizedDescription)
            }
            let err: NSError?
            if let jsonResult = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers) as? NSDictionary {
                if(err != nil) {
                    print("JSON Error (err!.localizedDescription)")
                }
                if let results: NSArray = jsonResult["results"] as? NSArray {
                    dispatch_async(dispatch_get_main_queue(), {
                        self.tableData = results
                        self.Indextableview.reloadData()
                    })
                }
            }
        })

        task.resume()

    }

在更新到XCode7之后，它给出这个错误：从(_，_，_)类型的抛出函数的无效转换抛出->void到非抛出函数类型(NSData？，NSURLResponse？，NSError？)->void。在队列中，任务放在哪里。

谢谢

推荐答案

您需要按如下方式实现do try catch错误处理：

import UIKit
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

extension URL {
    func asyncDownload(completion: @escaping (_ data: Data?, _ response: URLResponse?, _ error: Error?) -> ()) {
        URLSession.shared
            .dataTask(with: self, completionHandler: completion)
            .resume()
    }
}

let jsonURL = URL(string: "https://api.whitehouse.gov/v1/petitions.json?limit=100")!
let start = Date()
jsonURL.asyncDownload { data, response, error in

    print("Download ended:", Date().description(with: .current))
    print("Elapsed Time:", Date().timeIntervalSince(start), terminator: " seconds
")
    print("Data size:", data?.count ?? "nil", terminator: " bytes

")

    guard let data = data else {
        print("URLSession dataTask error:", error ?? "nil")
        return
    }

    do {
        let jsonObject = try JSONSerialization.jsonObject(with: data)
        if let dictionary = jsonObject as? [String: Any],
            let results = dictionary["results"] as? [[String: Any]] {
            DispatchQueue.main.async {
                results.forEach { print($0["body"] ?? "", terminator: "

") }
      //        self.tableData = results
      //        self.Indextableview.reloadData()
            }
        }
    } catch {
        print("JSONSerialization error:", error)
    }
}
print("
Download started:", start.description(with: .current))

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