Question

我正在尝试创建一个通用函数，以从Web服务下载json，当前此功能很好用，但是我不确定这是一个好方法还是最好的方法。

是否可以将其作为URLSession的一部分？，可以将其用作类函数吗？，还有没有更好的方法来处理错误？

enum HTTPMethod: String{
case GET
case POST
}

extension URLSession{

class func genericFetchData<T: Codable>(urlString: String, parameters:[String: Any]?, method: HTTPMethod = .GET,  completion: @escaping(T?, NSError?) -> Void) {

    guard var urlComponents = URLComponents(string: urlString) else {
        let error = NSError(domain: urlString, code: 400, userInfo: ["Error " : "URL error."])
        completion(nil, error)
        return
    }

    if let items = create(parameters) {
        urlComponents.queryItems = items
    }

    guard let url = urlComponents.url else {
        let error = NSError(domain: "Parameters", code: 400, userInfo: ["Error " : "Unable to create url using parameter you inlcuded."])
        completion(nil, error)
        return
    }

    var request = URLRequest(url: url)

    request.httpMethod = method.rawValue
    URLSession.shared.dataTask(with: request) { (data, res, error) in

        guard let data = data else{
            let error: NSError = error! as NSError
            completion(nil, error)
            return
        }

        let decoder = JSONDecoder()
        decoder.keyDecodingStrategy = .convertFromSnakeCase

        if let obj = try? decoder.decode(T.self, from: data){
            completion(obj, nil)
        } else{
            let error = NSError(domain: urlString, code: 500, userInfo: ["Error" : "The data couldn’t be read because it isn’t in the correct format."])
            completion(nil, error)
        }

        }.resume()
}

private static func create(_ parameters: [String: Any]?) -> [URLQueryItem]? {
    var queryItems = [URLQueryItem]()

    guard let unwrappedParameters = parameters else {
        return nil
    }

    for (key, value) in unwrappedParameters {
        let strValue = String(describing: value)
        queryItems.append(URLQueryItem(name: key, value: strValue))
    }

    return queryItems
}

}

URL会话通用功能

0 个答案: