Enjoy !

ServiceMangaer.swift

enum NetworkError : Error {
    case cityNotFound
    case timeOut
}

class WeatherService {
    
    static func getData(city : String , completionHandler : @escaping (Result<WeatherResponse, NetworkError>) -> ()) {
        
        guard let url = URL(string: "\(city)") else {
            return
        }
        
        var request = URLRequest(url: url)
        request.httpMethod = "GET"
        
        URLSession.shared.dataTask(with: request) { data, response, error in
            guard data != nil else {
                completionHandler(.failure(NetworkError.timeOut))
                return
            }
            
            do {
                let decoder = JSONDecoder()
                let decodedData = try decoder.decode(WeatherResponse.self, from: data!)
                
                DispatchQueue.main.async {
                    completionHandler(.success(decodedData!))
                }
            } catch {
                DispatchQueue.main.async {
                    completionHandler(.failure(NetworkError.cityNotFound))
                }
            }
            
        }.resume()
        
    }
}