Swift4 標高API

call.swift

//呼び出し側の記述例

        //WebAPI
        let webApi = Geospatial()
        webApi.getElevation(coordinate, closure: { (json) in
            
            if let elevation = json?.elevation {
                print(elevation)
            }
        })

Geospatial.swift

import CoreLocation


class Geospatial: NSObject {

    //JSON 全体の構成
    struct Json: Codable {
        let elevation: Double
        let hsrc: String
    }
}


// MARK: -
extension Geospatial {
    
    //Web 問い合わせ
    public func getElevation(_ coordinate: CLLocationCoordinate2D?, closure:@escaping (_ json: Json?)->()) {
        
        //前提条件
        guard let coordinate = coordinate else {
            return
        }
        
        
        let url_text = String(format:"https://cyberjapandata2.gsi.go.jp/general/dem/scripts/getelevation.php?lat=%f&lon=%f&outtype=JSON", coordinate.latitude, coordinate.longitude)
        
        if let url = URL(string: url_text) {
            
            let task = URLSession.shared.dataTask(with: url, completionHandler: { (data, responce, error) in
                
                //前提条件
                if let error = error {
                    print(error)
                    return
                }
                
                //Jsonをパース
                let json = self.decode(data)
                
                //*** callback ***
                DispatchQueue.main.async() {
                    closure(json)
                }
            })
            
            task.resume()
        }
    }
    
    
    //JSONデータの読み込み
    private func decode(_ json: Data?) -> Json? {
        
        //前提条件
        guard let json = json else {
            return nil
        }
        
        //データ読み込み
        let decoder = JSONDecoder()
        if let data = try? decoder.decode(Json.self, from: json) {
            //正常終了
            return data
        }
        
        //異常終了
        return nil
    }
}