Question

我正在使用天气API中的SwiftyJson解析json数据。我有一个可选数据列表，我将它添加到单个保护语句中，使代码看起来更简单，更有效。但遗憾的是，在可选项列表中，我有时会从已解析的API数据中获取nil值，因此该语句将转到else并且不返回任何内容。我是否必须将guard else语句放到每个可选项中，或者有一种方法可以继续并在else语句中返回找到的非零值？

这是我的代码：

dispatch_async(dispatch_get_main_queue(), {
                 let jsonContent = JSON(data: data!)

                 guard  let cTemp = jsonContent["currently"]["temperature"].double,
                        let cFeelsLike = jsonContent["currently"]["apparentTemperature"].double,
                        let cHumidity = jsonContent["currently"]["humidity"].double,
                        let cDewPoint = jsonContent["currently"]["dewPoint"].double,
                        let cPressure = jsonContent["currently"]["pressure"].double,
                        let cVisibility = jsonContent["currently"]["visibility"].double,
                        let cWindSpeed = jsonContent["currently"]["windSpeed"].double,
                        let cWindDirection = jsonContent["currently"]["windBearing"].double,
                        let cRainChance = jsonContent["currently"]["precipProbability"].double,
                        let cIconString = jsonContent["currently"]["icon"].string,
                        let cSummary = jsonContent["currently"]["summary"].string,
                        let cDailySummary = jsonContent["daily"]["summary"].string

                        else{

                            self.messageFrame.removeFromSuperview()
                          return
                        }

以下是解析更改故事板上标签的数据后的代码。

 if self.segmentedControl.selectedSegmentIndex == 0 {
                    UIApplication.sharedApplication().applicationIconBadgeNumber = Int(round(cTemp))
                    self.tempLabel.text = String(Int(round(cTemp))) + "˚"
                    self.humidityLabel.text = String(Int(round(cHumidity*100))) + "%"
                    self.pressureLabel.text = String(Int(round(cPressure))) +  NSLocalizedString(" mBar", comment: "milli Bar")
                    self.windSpeedLabel.text = String(Int(round(cWindSpeed))) + NSLocalizedString(" Km/h", comment: "Kilo fe El sa3a")
                    self.realFeelLabel.text = String(Int(round(cFeelsLike))) + "˚"
                    self.windDirectionLabel.text = self.windDirectionNotation(cWindDirection)
                    self.rainChanceLabel.text = String(Int(round(cRainChance * 100))) + "%"
               //     self.visibilityLabel.text = String(Int(round(cVisibility))) + NSLocalizedString(" Km", comment: "Km")
                    self.descriptionLabel.text = cSummary
                    self.descriptionMoreLabel.text = cDailySummary
                    self.bgImage.image = self.bgPicker(cIconString) //Change BG according to currently weather conditions.

                } else {
                    self.tempLabel.text = String(Int(round(cTemp))) + "˚"
                    self.humidityLabel.text = String(Int(round(cHumidity*100))) + "%"
                    self.pressureLabel.text = String(Int(round(cPressure))) + NSLocalizedString(" mBar", comment: "milli Bar")
                    self.windSpeedLabel.text = String(Int(round(cWindSpeed))) + NSLocalizedString(" mph", comment: "meel fee el sa3a")
                    self.realFeelLabel.text = String(Int(round(cFeelsLike))) + "˚"
                    self.windDirectionLabel.text = self.windDirectionNotation(cWindDirection)
                    self.rainChanceLabel.text = String(Int(round(cRainChance * 100))) + "%"
              //      self.visibilityLabel.text = String(Int(round(cVisibility))) + NSLocalizedString(" mi", comment: "meel")
                    self.descriptionLabel.text = cSummary
                    self.descriptionMoreLabel.text = cDailySummary
                    self.bgImage.image = self.bgPicker(cIconString) //Change BG according to currently weather conditions.
                }

Answer 1

将标签text设置为nil或Optional字符串是合法的。因此，对于每个项目，使用可选链接打开它并设置相应的标签text。

不幸的是我不知道SwiftyJSON，但是如果这只是一个字典，你会怎么做：

// here is some test data
let content = ["currently":["temperature":"21"]]
let lab = UILabel()
// this is what you would do
lab.text = (content["currently"] as? NSDictionary)?["temperature"] as? String

重点是最后一行。如果我们获得nil，我们会将标签text设置为nil并且不会造成任何损害。如果我们得到了我们的字符串，我们将标签的text设置为一个可选的包装字符串并且不会造成任何损害。

选项的守卫陈述在快速

1 个答案: