swift - 在 Swift 中将 DMS 坐标从 String 解析和转换为 Double 的更好方法

Question

所以我有一些坐标看起来像

N47° 15' 36.75",E011° 20' 38.28",+001906.00

我创建了一个类来解析并将它们转换为 double

struct PLNWaypointCoordinate {
    var latitude: Double = 0.0
    var longitude: Double = 0.0

    init(coordinateString: String) {
        self.latitude = convertCoordinate(string: coordinateString.components(separatedBy: ",")[0])
        self.longitude = convertCoordinate(string: coordinateString.components(separatedBy: ",")[1])
    }

    private func convertCoordinate(string: String) -> Double {
        var separatedCoordinate = string.characters.split(separator: " ").map(String.init)

        let direction = separatedCoordinate[0].components(separatedBy: CharacterSet.letters.inverted).first
        let degrees = Double(separatedCoordinate[0].components(separatedBy: CharacterSet.decimalDigits.inverted)[1])
        let minutes = Double(separatedCoordinate[1].components(separatedBy: CharacterSet.decimalDigits.inverted)[0])
        let seconds = Double(separatedCoordinate[2].components(separatedBy: CharacterSet.decimalDigits.inverted)[0])

        return convert(degrees: degrees!, minutes: minutes!, seconds: seconds!, direction: direction!)
}

    private func convert(degrees: Double, minutes: Double, seconds: Double, direction: String) -> Double {
        let sign = (direction == "W" || direction == "S") ? -1.0 : 1.0
        return (degrees + (minutes + seconds/60.0)/60.0) * sign
    }

}

我的问题是，正如标题所说，是否有更好、更安全的方式来执行此转换？

我在这里选择的最后一种方法。抱歉，我找不到引用它的链接。

Answer 1

这是一个更通用的版本，作为 CLLocationCoordinate2D 的扩展。

它用正则表达式解析字符串并考虑

• 参数之间的可选空格。
• 方向在字符串的开头或结尾，E 和 O 均表示东。
• 分钟 ('′) 和秒 ("″) 的不同字符。

---

extension CLLocationCoordinate2D {

    init?(coordinateString: String) {
        let directionIsPrefix = "NEOWS".contains(coordinateString.prefix(1))
        let pattern = directionIsPrefix
            ? "([NOEWS])\\s?(\\d{1,2})°\\s?(\\d{1,2})['′]\\s?(\\d{1,2}\\.?(\\d+)?)[\"″]"
            : "(\\d{1,2})°\\s?(\\d{1,2})['′]\\s?(\\d{1,2}\\.?(\\d+)?)[\"″]\\s?([NOEWS])"

        var latlon = [Double]()
        do {
            let regex = try NSRegularExpression(pattern: pattern)
            let matches = regex.matches(in: coordinateString, range: NSRange(coordinateString.startIndex..., in: coordinateString))
            guard matches.count == 2 else { return nil }

            for match in matches {
                let m1 = coordinateString[Range(match.range(at:1), in: coordinateString)!]
                let m2 = coordinateString[Range(match.range(at:2), in: coordinateString)!]
                let m3 = coordinateString[Range(match.range(at:3), in: coordinateString)!]
                let lastIndex = directionIsPrefix ? 4 : 5
                let m4 = coordinateString[Range(match.range(at:lastIndex), in: coordinateString)!]
                let value : Double
                if directionIsPrefix {
                    let sign = "NEO".contains(m1) ? 1.0 : -1.0
                    value = sign * (Double(m2)! + Double(m3)!/60.0 + Double(m4)!/3600.0)
                } else {
                    let sign = "NEO".contains(m4) ? 1.0 : -1.0
                    value = sign * (Double(m1)! + Double(m2)!/60.0 + Double(m3)!/3600.0)
                }
                latlon.append(value)
            }
        } catch {
            print(error)
            return nil
        }
        self.init(latitude: latlon[0], longitude: latlon[1])
    }
}