ApiService: Swift+URLSession

ApiService.swift

class ApiService {
    
    static let sharedInstance = ApiService()
    
    let BASE_URL = "https://restcountries.eu"
    
    // MARK: - List of countries
    func countries(_ completion: @escaping(_ result: [Country]?, _ error: Error?) -> Void) {
        
        let urlString = BASE_URL + "/rest/v2/all"
        guard let url = URL(string: urlString) else { return }
        
        URLSession.shared.dataTask(with: url) { (data, response, error) in
            if error != nil {
                completion(nil, error)
            }
            
            guard let data = data else { return }
            
            //Implement JSON decoding and parsing
            do {
                
//                let jsonResponse = try JSONSerialization.jsonObject(with:
//                    data, options: [])
//                print(jsonResponse) // Uncomment for debug purposes
                
                let countriesData = try JSONDecoder().decode([Country].self, from: data)
                // In case of single root key with a value as array,
                // we can use something like this: [String : [Vehicle]].self
                
                DispatchQueue.main.async {
                    completion(countriesData, nil)
                }
            } catch let jsonError {
                print(jsonError)
            }
        }.resume()
    }
}