无法转换“字符串”类型的值？到预期的参数类型'CLLocationDegrees'（又名'Double'）

Question

我尝试在单元格中显示帖子创建者与当前用户之间的距离。

我现在的错误是

无法转换“字符串”类型的值？到预期的参数类型'CLLocationDegrees'（又名'Double'）

在以下代码中：

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    if let lastLocation = locations.last {
        let geoCoder = CLGeocoder()

        let myLocation = CLLocation(latitude: lastLocation.coordinate.latitude, longitude: lastLocation.coordinate.longitude)

/*Here the error*/ let myBuddysLocation = CLLocation(latitude: job!.distance, longitude: job!.distance)

        let distance = myLocation.distance(from: myBuddysLocation) / 1000
        print(String(format: "The distance to my buddy is %.01fkm", distance))
    }
}

这是我的 JobClass：

class Job {

var distance: String?
let ref: DatabaseReference!

init(distance: String? = nil) {
    self.distance = distance
    ref = Database.database().reference().child("jobs").childByAutoId()
}

init(snapshot: DataSnapshot){
    ref = snapshot.ref
    if let value = snapshot.value as? [String : Any] {
        distance = value["distance"] as? String
    }
}

func save() {
    let newPostKey = ref.key
            let postDictionary = [
                "distance" : self.distance!
                ] as [String : Any]
            self.ref.setValue(postDictionary)
}
}

我希望有人知道如何解决它，如果有帮助，我可以添加更多代码 // 我是编码新手

Answer 1

错误是不言自明的：您尝试设置String? 而不是CLLocationDegrees，但您甚至可以使用Double 类型。

有几种方法可以解决这个问题：

1) 您可以按如下方式更改您的类定义：

   class Job {

          // Change distance to Double and set a default value instead of optional
          var distance: Double = 0.0
          let ref: DatabaseReference!

          // Change the init
          init(distance: Double = 0.0) {
              self.distance = distance
              ref = Database.database().reference().child("jobs").childByAutoId()
          }

          //You have to change all your distance to Double
          init(snapshot: DataSnapshot){
              ref = snapshot.ref
              if let value = snapshot.value as? [String : Any] {
                 // So change this cast
                  distance = value["distance"] as Double
              }
          }
         }

2) 您可以尝试将 String? 转换为 Double，但我不建议这样做。

无论如何，这是你可以做到的：

   if let dist = Double(job!.distance){
          let myBuddysLocation = CLLocation(latitude: dist, longitude: dist) -> Error Appears in this Line

           let distance = myLocation.distance(from: myBuddysLocation) / 1000
           print(String(format: "The distance to my buddy is %.01fkm", distance))
   }

Answer 2

实际上在你的函数中唯一的问题是你传递字符串值来代替你需要像这样改变的双精度值。

let myBuddysLocation = CLLocation(latitude: Double.init(job!.distance) ?? 0.0, longitude: Double.init(job!.distance) ?? 0.0) 

你需要像这样改变你的功能

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    if let lastLocation = locations.last {
        let geoCoder = CLGeocoder()

        let myLocation = CLLocation(latitude: lastLocation.coordinate.latitude, longitude: lastLocation.coordinate.longitude)

        let myBuddysLocation = CLLocation(latitude: Double.init(job!.distance) ?? 0.0, longitude: Double.init(job!.distance) ?? 0.0) 

        let distance = myLocation.distance(from: myBuddysLocation) / 1000
        print(String(format: "The distance to my buddy is %.01fkm", distance))
    }
}

Answer 3

这是正常的，因为距离应该是 Double 值。将其更改为：var distance: Double? 应该更正它。 或者将值解析为 Double let myBuddysLocation = CLLocation(latitude: Double(distance)!, longitude: Double(distance)!)

我建议您避免使用!，因为如果字符串不是数字，它可能会产生致命错误，您可以使用guard 来保护值，或者像下面的例子一样：

if let latitude = Double(distance) {
    let myBuddysLocation = CLLocation(latitude: latitude, longitude: latitude)
}