使用时属性显示为 nil 但在使用前打印到调试控制台？

Question

如果有任何其他问题可能与此问题有关，请告诉我，以便我尝试提供更多详细信息。我大约一周了，但似乎找不到问题所在。这可能会让我想把电脑扔到墙上，但我似乎想不通:(

问题似乎与坐标变量有关，但问题仍然可能与类的构造方式有关，但我无法确定它们的构造方式.
我能够在发出请求之前将当前位置坐标打印到屏幕上，但是在调用将发送的方法时 JSON 中出现以下错误api请求

"status" : "INVALID_REQUEST",

Google 文档声称：

"INVALID_REQUEST generally indicates that a required query parameter (location or radius) is missing."

我遇到的是：

使用硬编码坐标，我可以进行搜索并 return JSON 成功。
我能够成功获取当前位置坐标。
不过；我无法将当前位置坐标插入到搜索查询中。

这是一段很好的代码，我相信这是解决问题所需要的全部。我感谢任何可能导致解决问题的建议：

// all classes have their own swift file

class ViewController: UIViewController, CLLocationManagerDelegate
{

let currentLocation = CurrentLocation()
let downloadData    = DownLoadData()

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>)
{
    if !didFindMyLocation
    {
        let myLocation: CLLocation = change![NSKeyValueChangeNewKey] as! CLLocation
        currentLocation.coordinate = myLocation.coordinate
        currentLocation.latitude   = myLocation.coordinate.latitude
        currentLocation.longitude  = myLocation.coordinate.longitude

        didFindMyLocation = true

        print(currentLocation.coordinates) // prints coordinates correctly

        downLoadData.downloadAllLocations({ () -> () in  //request I am attempting to make that outputs,
        //"status" : "INVALID_REQUEST",
        })
    }
}

class CurrentLocation: NSObject, CLLocationManagerDelegate
{
override init()
{
    super.init()
}

var locationManager = CLLocationManager()

//THE CULPRITS!
var latitude   : CLLocationDegrees!
var longitude  : CLLocationDegrees!

}

// typealias in a swift file of its own.

import foundation

typealias DownLoadComplete = () -> ()


class DownloadData: NSObject
{
let currentLocation = CurrentLocation()

override init()
{
    super.init()
}

func downloadAllLocations(completed: DownloadComplete)
{
    //hardcoded coordinates output correct JSON Response. So Why Cant I Interpolate the coordinates from my current location???
    let URL_Search = "https://maps.googleapis.com/maps/api/place/nearbysearch/json?"
    let urlString  = "\(URL_Search)location=\(currentLocation.latitude),\(currentLocation.longitude)&radius=\(searchRadius)&types=\(searchType)&key=\(API_ServerKey)"

    let url = NSURL(string: urlString)!
    print(url) // outputs nil,nil in the currentLocation.latitude and currentLocation.longitude spots
    Alamofire.request(.GET,url).responseJSON { (response) -> Void in

        switch response.result
        {
        case .Success:
            if let value = response.result.value
            {
                let json = JSON(value)
                print(json) // If hardcoded coordinates are inserted then I the json is outputted. If current location is attempted then I receive an INVALID_REQUEST error.

                if let results = json["results"].array
                {
                    for result in results {
                        if let places = result["place"].string
                        {
                            self.places = place
                        }
                    }
                }
            }
        case .Failure(let error):
            print(error)
        }

        completed()
     }
  }

}

在我发送请求之前通过 print(currentLocation.coordinates) 测试输出（downLoadData.downLoadAllLocation[调用了 print(url)]）输出到调试控制台是：

CLLocationCoordinate2D(latitude: 37.33233141, longitude: -122.0312186) https://maps.googleapis.com/maps/api/place/nearbysearch/json?location=nil,nil ...etc

这里的问题是插入到搜索查询中的坐标显示为 nil，nil？我试过操纵代码。但运气不好……它们被打印出来似乎很奇怪，但随后在搜索中它们显示为零。怎么可能？？

Answer 1

DownloadData class 指的是一个 currentLocation 变量（大概是 CurrentLocation 的一个实例，但是这个变量没有在你的代码示例中的任何地方定义。我假设它是 ViewController 的成员变量，在这种情况下，问题是：DownloadData 如何知道它？

您可能需要将 currentLocation 作为参数传递给 downloadData.downloadAllLocations()。

使用时属性显示为 nil 但在使用前打印到调试控制台？

Properties appearing as nil when used but print to debug console prior to use?

ios

json

swift

google-maps

google-places-api