ios - 尝试重用 NSURL 时获取 Nil

Question

我正在尝试使用 https://developer.forecast.io/ 获取某些位置的天气接口(interface)。API调用格式为https://api.forecast.io/forecast/APIKEY/LATITUDE,LONGITUDE

我可以从一个位置获得响应，但是当我尝试更改位置并再次使用 NSURL 获取天气时，NSURL 返回 Nil。为什么会这样以及如何处理？

谁能帮帮我？谢谢。

func getCurrentWeatherData() -> Void {
        let baseURL = NSURL(string: "https://api.forecast.io/forecast/\(apiKey)/")
        var forecastURL = NSURL(string: "36.107728,-112.113040", relativeToURL: baseURL)
        let sharedSession = NSURLSession.sharedSession()
        let downloadTask: NSURLSessionDownloadTask = sharedSession.downloadTaskWithURL(forecastURL!, completionHandler: {
            (location: NSURL!, response: NSURLResponse!, error: NSError!) -> Void in

            //var urlContents = NSString(contentsOfURL: location, encoding: NSUTF8StringEncoding, error: nil)
            if (error == nil) {
                let dataObject = NSData(contentsOfURL: location)
                let weatherDictionary: NSDictionary = NSJSONSerialization.JSONObjectWithData(dataObject!, options: nil, error: nil) as NSDictionary
                let currentWeather = Current(weatherDictionary: weatherDictionary)

                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    self.iconView.image = currentWeather.icon!
                    self.currentTimeLabel.text = "At \(currentWeather.currentTime!) it is"
                    self.temperatureLabel.text = "\(Double(currentWeather.temperature-32) * 0.56)"
                    self.summaryLabel.text = "\(currentWeather.summary)"
                    self.refreshActivityIndicator.stopAnimating()
                    self.refreshActivityIndicator.hidden = true
                    self.refreshButton.hidden = false
                })
            } else {
                let networkIssueController = UIAlertController(title: "Error", message:"Unable to load data. Connectivity error!", preferredStyle: .Alert)
                let okButton = UIAlertAction(title: "OK", style: .Default, handler:nil)
                networkIssueController.addAction(okButton)
                let cancelButton = UIAlertAction(title:"Cancel", style: .Cancel, handler:nil)
                networkIssueController.addAction(cancelButton)
                self.presentViewController(networkIssueController, animated: true, completion: nil)
                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    self.refreshActivityIndicator.stopAnimating()
                    self.refreshActivityIndicator.hidden = true
                    self.refreshButton.hidden = false
                })
            }
        })
        downloadTask.resume()

        var forecastURL2 = NSURL(string: "https://api.forecast.io/forecast/\(apiKey)/36.861941, -111.374420")
        let sharedSession2 = NSURLSession.sharedSession()
        **//forcastURL2 returns Nil**
        let downloadTask2: NSURLSessionDownloadTask = sharedSession2.downloadTaskWithURL(forecastURL2!, completionHandler: {
            (location: NSURL!, response: NSURLResponse!, error: NSError!) -> Void in

            //var urlContents = NSString(contentsOfURL: location, encoding: NSUTF8StringEncoding, error: nil)
            if (error == nil) {
                let dataObject = NSData(contentsOfURL: location)
                let weatherDictionary: NSDictionary = NSJSONSerialization.JSONObjectWithData(dataObject!, options: nil, error: nil) as NSDictionary
                let currentWeather = Current(weatherDictionary: weatherDictionary)

                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    self.iconView2.image = currentWeather.icon!
                    self.temperatureLabel2.text = "\(Double(currentWeather.temperature-32) * 0.56)"
                    self.summaryLabel.text = "\(currentWeather.summary)"
                    self.refreshActivityIndicator.stopAnimating()
                    self.refreshActivityIndicator.hidden = true
                    self.refreshButton.hidden = false
                })
            } else {
                let networkIssueController = UIAlertController(title: "Error", message:"Unable to load data. Connectivity error!", preferredStyle: .Alert)
                let okButton = UIAlertAction(title: "OK", style: .Default, handler:nil)
                networkIssueController.addAction(okButton)
                let cancelButton = UIAlertAction(title:"Cancel", style: .Cancel, handler:nil)
                networkIssueController.addAction(cancelButton)
                self.presentViewController(networkIssueController, animated: true, completion: nil)
                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    self.refreshActivityIndicator.stopAnimating()
                    self.refreshActivityIndicator.hidden = true
                    self.refreshButton.hidden = false
                })
            }
        })
        downloadTask2.resume()

    }

Answer 1

您使用的 URL ("https://api.forecast.io/forecast/\(apiKey)/36.861941, -111.374420") 应该格式正确，并且根据 Apple 的说法，符合RFC2396 .如果不是 NSURL 将返回 nil。

您使用的网址不正确。例如空格应该使用 "%20" 进行转义。对于您的情况，我认为您可以删除空格。