"How to use Codable Protocol for a Networking Layer "

Question

我正在尝试为我的应用构建一个网络层，以便我完成项目

我遇到错误

"Cannot invoke 'decode' with an argument list of type '(Codable, from: Data)'" I think its happening because of error type or a mismatch Help me resolve this issue

enum Type:String {
    case GET
    case POST
    case PUT
    case DELETE
}


func networkRequest(MethodType:Type, url:String, codableType:Codable) {

    guard let getUrl = URL(string: url) else {return}

    if MethodType == Type.GET  {

        URLSession.shared.dataTask(with: getUrl) { (data, response, err) in

            if let urlRes = response as? HTTPURLResponse{

                if 200...300 ~= urlRes.statusCode {

                    guard let data = data else {return}

                    do {
                        let newData = try JSONDecoder().decode(codableType.self, from: data)
                    }
                    catch let jsonerr {
                        print("Error Occured :"+jsonerr.localizedDescription)
                    }
                }


            }
        }.resume()

    }

}

Answer 1

JSONDecoder 需要符合 Decodable 的具体类型。协议不能符合自身。

您可以使该方法通用

func networkRequest<T : Decodable>(MethodType: Type, url: String, codableType: T.Type) {
...
   let newData = try JSONDecoder().decode(T.self, from: data)

并称之为

networkRequest(MethodType: .GET, 
                      url: "https://test.com/api", 
              codableType: News.self)

Answer 2

泛型可以解决这个问题。

首先介绍一个泛型类型参数：

func networkRequest<T: Decodable>(MethodType:Type, url:String)
                   ^^^^^^^^^^^^^^

现在您可以使用 T.self 作为要解码的类型：

try JSONDecoder().decode(T.self, from: data)

此外，您可以考虑添加一个完成处理程序，否则您获取的值将丢失：

func networkRequest<T: Decodable>(MethodType:Type, url:String, completionHandler: (T) -> Void)

用法：

networkRequest(MethodType: .GET, url: ...) {
    (myStuff: MyType) in
    ...
}

"How to use Codable Protocol for a Networking Layer "

"How to use Codable Protocol for a Networking Layer "

encoding

decoding

ios

swift

swift4