Cannot convert value of type 'Dictionary<String, Any>?' to expected argument type 'Data'

Question

I am still new to swift and i am trying to fetch json data and pass it to the next view as an object which i created. However, i am getting this error Cannot convert value of type 'Dictionary?' to expected argument type 'Data' when i try to user the decoder class. I am not sure what to do to fix it. I have tried changing Dictionary?' to Data in my completion handler but i am still getting errors.

This is my code :

Service call

    class ServiceCall: NSObject, ServiceCallProtocol, URLSessionDelegate {



    let urlServiceCall: String?
    let country: String?
    let phone: String?
     var search: SearchResultObj?

    init(urlServiceCall: String,country: String, phone: String){
        self.urlServiceCall = urlServiceCall
        self.country = country
        self.phone = phone
    }


    func fetchJson(request: URLRequest, customerCountry: String, mobileNumber: String, completion: ((Bool, Dictionary<String, Any>?) -> Void)?){

        let searchParamas = CustomerSearch.init(country: customerCountry, phoneNumber: mobileNumber)
        var request = request
        request.httpMethod = "POST"
        request.httpBody = try?  searchParamas.jsonData()
        request.addValue("application/json", forHTTPHeaderField: "Content-Type")

        let session = URLSession.shared
        let task = session.dataTask(with: request, completionHandler: { data, response, error -> Void in
            do {
                let json = try JSONSerialization.jsonObject(with: data!) as! Dictionary<String, Any>
                let status = json["status"] as? Bool
                if status == true {
                    print(json)
                }else{
                    print(" Terrible failure")
                }
            } catch {
               print("Unable to make an api call")
            }
        })

        task.resume()

    }


  }

SearchViewModel

func searchDataRequested(_ apiUrl: String,_ country: String,_ phone:String) {

    let service = ServiceCall(urlServiceCall: apiUrl, country: country, phone: phone)
    let url = URL(string: apiUrl)
    let request = URLRequest(url: url!)
    let country = country
    let phone = phone

    service.fetchJson(request: request, customerCountry: country, mobileNumber: phone)
    { (ok, json) in
        print("CallBack response : \(String(describing: json))")
        let decoder = JSONDecoder()
        let result = decoder.decode(SearchResultObj.self, from: json)

        print(result.name)
        // self.jsonMappingToSearch(json as AnyObject)

    }
}

New error:

Answer 1

You are going to deserialize the JSON twice which cannot work.

Instead of returning a Dictionary return Data , this mistake causes the error, but there are more issues.

func fetchJson(request: URLRequest, customerCountry: String, mobileNumber: String, completion: (Bool, Data?) -> Void) { ...

Then change the data task to

let task = session.dataTask(with: request, completionHandler: { data, response, error -> Void in

    if let error = error { 
        print("Unable to make an api call", error)
        completion(false, nil)
        return 
    }
    completion(true, data)
})

and the service call

service.fetchJson(request: request, customerCountry: country, mobileNumber: phone) { (ok, data) in
    if ok {
        print("CallBack response :", String(data: data!, encoding: .utf8))
        do {
            let result = try JSONDecoder().decode(SearchResultObj.self, from: data!)
            print(result.name)
            // self.jsonMappingToSearch(json as AnyObject)
        } catch { print(error) }
    }
}

And you have to adopt Decodable in ServiceCall

class ServiceCall: NSObject, ServiceCallProtocol, URLSessionDelegate, Decodable { ...

Further I highly recommended to separate the class model from the code to retrieve the data.

Answer 2

The data returned from session's task can either be serialized with JSONSerialization or decode it with JSONDecoder

 let task = session.dataTask(with: request, completionHandler: { data, response, error -> Void in

either

 let json = try JSONSerialization.jsonObject(with: data!) as! Dictionary<String, Any>

OR

let result = try  decoder.decode([item].self,data!)

the second argument of the decode method expects a parameter of type Data not Dictionary

you have to only edit the completion of fetchJson to return Bool,Data instead of Bool,Dictionary,and remove JSONSerialization code from it