How to pass Encodable or Decodable as parameter in Swift 4?

Question

I am learning JSONParsing. I followed tutorials and what I got is this:

    guard let url = URL(string: "http://localhost/test-api/public/api/register") else { return }

    var request  = URLRequest(url: url)

    request.httpMethod = "POST"

    let newUser = User.init(name: self.collectionTF[0].text, email: self.collectionTF[1].text, password: self.collectionTF[2].text)

    do {

        let jsonBody = try JSONEncoder().encode(newUser)

        request.httpBody = jsonBody

    } catch { }

    URLSession.shared.dataTask(with: request) { (data, response, error) in

        guard let data = data else { return }

        do {

            let json = try JSONSerialization.jsonObject(with: data) as? [String:Any]

            print(json!)

            DispatchQueue.main.async {

            if json!["status"] as! Int == 200
            {
                GeneralHelper.shared.keepLoggedIn()

                NavigationHelper.shared.moveToHome(fromVC: self)
            }

            }

        } catch { print(error.localizedDescription)}

        }.resume()

Ok, this is what I have done for register. Now, I want to create a Helper, which will do the same thing with @escaping as I we all need the parsed JSON in return.

So, I am passing the endPoint as String and then trying to pass this newUser which is a Encodable , it can be a Decodable as well in future, but it throws an error Cannot invoke 'encode' with an argument list of type '(Codable)' . Can anyone please help? And, is it better this way, by calling this function multiple times when it comes to JSONParsing ?

Edit: - So, I am now using the networkRequestfunction and here is what I have done.

 let newData = User.init(name: "Rob", email: "abc@gmail.com", password: "12345678")

ApiHelper.sharedInstance.networkRequest_Post(urlString: "register", header: nil, encodingData: newData) { (response: User, urlRes, error) in
        <#code#> }

Now, it gives me this error: Cannot convert value of type '(User, _, _) -> ()' to expected argument type '(_?, HTTPURLResponse?, Error?) -> ()' . Any help?

Answer 1

I have used the same functionality in my project

Hope the below code will help

    func networkRequest_Post<T: Decodable, Q: Encodable>(urlString: String,header:[String:String]?,encodingData: Q,completion: @escaping (T?, HTTPURLResponse?, Error?) -> ()) {

    guard let url = URL(string: urlString) else { return }
    let config = URLSessionConfiguration.default
    config.timeoutIntervalForRequest = 300.0
    config.timeoutIntervalForResource = 300.0
    if header != nil{
        config.httpAdditionalHeaders = header
    }
    let session = URLSession(configuration: config)
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    do {
        let jsonBody = try JSONEncoder().encode(encodingData)
        request.httpBody = jsonBody
    } catch {}
    let task = session.dataTask(with: request) { (data,response, err) in

        if let response = response {
            print(response)
        }
        if let err = err {
            print("Failed to fetch data:", err.localizedDescription, "Error Description\(err)")
            return
        }
        guard let data = data else { return }
        do {
            print(String(data: data, encoding: String.Encoding.utf8) as Any)
            let dataReceived = try JSONDecoder().decode(T.self, from: data)
                completion(dataReceived,response as? HTTPURLResponse,err)
        } catch let jsonErr {
            print("Failed to serialize json:", jsonErr, jsonErr.localizedDescription)
            completion( nil,response as? HTTPURLResponse,jsonErr)
        }
    }
    task.resume()
}

Use -

         let newdata = User(name: "Abhi", email: "jhjhj@jhj.co", password: "123hguhj")
    networkRequest_Post(urlString: "YOUR_URL", header: nil, encodingData: newdata) { (RESPONSE_DATA:User?, URL_RESPONSE, ERROR) in
        // Do your network work here
    }

    struct User : Codable {
      var name: String?
      var email: String?
      var password: String?
    }

Answer 2

You can user Generics in following way...

func requestWith<T>(method: HTTPMethod, action: String,  params: Parameters?, for type: T.Type, success: @escaping (AnyObject) -> Void, failure: @escaping (AnyObject) -> Void) where T: Codable {


//do your stuff..your logic goes here..see below example

     guard let serverData = response.data else {
           return
        }

   do {
     let decoder = JSONDecoder()
     let responseData = try decoder.decode(type, from: serverData)
       success(responseData as AnyObject)
    } catch {
      print("Error = \(error.localizedDescription)")
       failure(error.localizedDescription as AnyObject)
   }

}