Swift3的许多问题:无法理解完成处理程序的新语法

Question

昨天我更新到新的Mac OS X Sierra和XCode 8,迫使我更新到Swift 3.0语法.在我的应用程序中,我有许多功能,如下所示:

fileprivate func requestFisheFieldWithHandler(_ url:String, completionHandler: @escaping (_ success: NSDictionary?, _ error: NSError?) -> Void) {

    let configuration = URLSessionConfiguration.default

    let url: URL = URL(string: url)!
    let urlRequest: URLRequest = URLRequest(url: url)

    let session = URLSession(configuration: configuration)

    let task = session.dataTask(with: urlRequest, completionHandler: { (data: Foundation.Data?, response: URLResponse?, error: NSError?) -> Void in

        if (error != nil) {
            //print(error?.code)
            //print(error)
            completionHandler(success: nil, error: error)
        }

        else {
            do {
                let responseJSON = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions()) as! [String: String]
                completionHandler(success: responseJSON, error:nil)
            }
            catch let error as NSError {
                completionHandler(success: nil, error:error)
            }
        }
    } as! (Data?, URLResponse?, Error?) -> Void)

    task.resume()
}

我收到此错误:

"无法转换类型的值'(数据？,URLResponse？,错误？) - > Void'到预期的参数类型'(数据？,URLResponse？,错误？) - >无效'"

此外,我还使用了许多关联数组来从下载的JSON文件中收集数据,如下所示:

for comune in response! {
                        self.comuni.append(comune["nome"] as! String)
                        self.comuniWithID[comune["nome"] as! String] = Int(comune["idcomune"] as! String)
}
DispatchQueue.main.async {
    self.myPicker.reloadComponent(1)
}

我得到的另一个错误是:

"Type'NSFastEnumerationIterator.Element'(又名'Any')没有下标成员"

拜托,有人会帮我纠正吗？因为我无法理解他们的意思,我的应用程序将于9月30日发布...

Answer 1

最重要的变化是在Swift 3中删除了闭包中的所有参数标签.

这是你的代码Swift 3兼容.

与往常一样,不要将Swift集合类型强制转换为Foundation对象.你将丢弃所有类型的信息.

并且不要在完成块返回值中使用注释,编译器可以推断出类型.如果需要⌥-click在符号上查找实际类型.

fileprivate func requestFisheFieldWithHandler(_ url:String, completionHandler: @escaping ([String: String]?, NSError?) -> Void) {

  let configuration = URLSessionConfiguration.default

  let url: URL = URL(string: url)!
  let urlRequest = URLRequest(url: url)

  let session = URLSession(configuration: configuration)

  let task = session.dataTask(with: urlRequest) { (data, response, error) -> Void in
    if (error != nil) {
      completionHandler(nil, error as NSError?)
    }

    else {
      do {
        let responseJSON = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions()) as! [String: String]
        completionHandler(responseJSON, nil)
      }
      catch let error as NSError {
        completionHandler(nil, error)
      }
    }
  }
  task.resume()
}

关于第二个错误你必须投射response!到比Any我更有意义的东西... in response as! [[String:Any]]