天气应用程序：“意外地发现零，同时解开一个可选值”swift3

Question

我正在处理天气API。收到错误在下面的代码：

fileprivate let openWeatherMapBaseURL = "http://api.openweathermap.org/data/2.5/weather" 
fileprivate let openWeatherMapAPIKey = "b7ac98fd9b59acbe6078468d865bd908" 

func getWeather(_ city: String) { 

    // This is a pretty simple networking task, so the shared session will do. 
    let session = URLSession.shared 

    let weatherRequestURL = URL(string:"http://api.openweathermap.org/data/2.5/weather?q=\(city)&APPID=\(openWeatherMapAPIKey)")! 

    let dataTask = session.dataTask(with: weatherRequestURL, completionHandler: { 
     (data: Data?, response: URLResponse?, error: NSError?) in 

     if let error = error{ 
     print("Error:\n\(error)") 
     } 

     else{ 
      print("Raw data:\n\(data!)\n") 
      let dataString = String(data: data!, encoding: String.Encoding.utf8) 
      print("Human-readable data:\n\(dataString!)") 

     } 
    } as! (Data?, URLResponse?, Error?) -> Void) 
    dataTask.resume() 
}} 

得到错误在这行：

let dataTask = session.dataTask(with: weatherRequestURL, completionHandler: { 

错误：

unexpectedly found nil while unwrapping an Optional value

做任何人知道究竟是什么解决办法吗？

Answer 1

你强行解开它

let weatherRequestURL = URL(string:"http://api.openweathermap.org/data/2.5/weather?q=\(city)&APPID=\(openWeatherMapAPIKey)")! 

，而不是做这样的

if let weatherRequestURL = URL(string:"http://api.openweathermap.org/data/2.5/weather?q=\(city)&APPID=\(openWeatherMapAPIKey)") { 
// do your stuff 

} 

Answer 2

用户这个

let requestURL: NSURL = NSURL(string: "http://api.openweathermap.org/data/2.5/weather?q=\(city)&APPID=\(openWeatherMapAPIKey)")! 
     let urlRequest: NSMutableURLRequest = NSMutableURLRequest(url: requestURL as URL) 
     let session = URLSession.shared 
     let task = session.dataTask(with: urlRequest as URLRequest) { 
      (data, response, error) -> Void in 

      let httpResponse = response as! HTTPURLResponse 
      let statusCode = httpResponse.statusCode 

      if (statusCode == 200) { 
       do{ 
        let jsonResponse = try JSONSerialization.jsonObject(with: data! as Data, options: .allowFragments) as? NSDictionary 
        print(jsonResponse) 
       }catch { 
        print("Error with Json: \(error)") 
       } 
      } 
     }