Question

我目前正在尝试构建一种计算当前位置与其他硬编码位置之间距离的方法。我最终会在表格视图中将这些距离显示为字符串。这些是我正在采取的步骤：

1）我有一个硬编码的词典库，每个词典都有一个“纬度”和“经度”的键值对。

2）从结构中提取此信息，如下所示：

 struct BarDetials {

 // other properties
 ....
 var lat: CLLocationDegrees?
 var long CLLocationDegrees?

 init(index: Int) {
 // initialize other properties
 // ...
 lat = specificBarDetail["latitude"] as! CLLocationDegrees!
 long = specificBarDetail["longitude"] as! CLLocationDegrees!

   }
 }

3）我使用另一个结构从这些坐标创建一个CLLocation实例数组，如下所示：

struct ConstructLocationsToCompare {

var latitude : [CLLocationDegrees?] = []
var longitude : [CLLocationDegrees?] = []
var barLocations : [CLLocation?] = []

init(){
    for index in 0...21 {
        var data = BarDetails(index: index)
        if data.lat != nil {
            latitude.append(data.lat!)
        }
        if data.long != nil {
            longitude.append(data.long!)
        }
        barLocations[index] = CLLocation(latitude: latitude[index]!, longitude: longitude[index]!)
       }

   }
}

4）然后我在MasterViewController（）中计算距离。

var latestLocation：AnyObject？，var currentLocation：CLLocation！和var distanceStringArray：[String？] = []是我的MasterViewController（）类的所有属性。

func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) {
    CLGeocoder().reverseGeocodeLocation(manager.location, completionHandler: { (placemarks, error) -> Void in

        // Get latest location and store it as a property of MasterViewController

        if self.latestLocation != nil {
            self.latestLocation = locations[locations.count - 1]

        // Print out the latest locaiton for debuging

        println("Latest Location")
        println("---------------")
        println(self.latestLocation)


        // Create an instance of ContructLocationsToCompare to get all locaiton data

        var getBarLocations = ConstructLocationsToCompare()

        // Get loop to calculate the distance you are away from each Bar

        var distanceDoubleArray : [Double?] = []

        for index in 0...21 {
            var distanceBetween : CLLocationDistance = self.latestLocation!.distanceFromLocation(getBarLocations.barLocations[index])
            var distanceInFeet = distanceBetween * 3.28084
            distanceDoubleArray[index] = distanceInFeet
            self.distancesStringArray.append( String(format: "%6.0 ft", distanceDoubleArray[index]!))

        }
    }
        //println(distanceBetween) or get error if it exists

        if error != nil {
            println("Error: " + error.localizedDescription)
            return
        }
        if placemarks.count > 0 {
            let pm = placemarks[0] as! CLPlacemark
            self.displayLocationInfo(pm)
        }

    })

}

5）最后，要显示我与每个位置的距离（在我的-cellForRowAtIndexPath中）：

           println("")
           println("")

           println("List of Locations")
           println("=================")
           println(self.distancesStringArray)

           println("")
           println("")
           println("")
           println("")




                 if self.distancesStringArray[indexPath.row]!.isEmpty == true{    
               futureCell.distanceAway?.text = "-" // I crash at this line ^^^^^^
           } else {
            futureCell.distanceAway?.text = self.distancesStringArray[indexPath.row]
                }

***我的distanceStringArray总是为空，因此我收到致命错误并且应用程序崩溃了。我该如何解决？事实是我声明了var latestLocation：AnyObject？，var currentLocation：CLLocation！和var distanceStringArray：[String？] = []属性我的MasterViewController（）类坏练习？如果不是这些属性需要作为不同的类型/以不同的方式声明？

为什么我的CLLocation实例数组是空的？

0 个答案: