How to display different form of data with single Model in swift

I am having a function for api request as below

  func getUsers(completion:@escaping (Result<[ResultItem],NetworkError>) -> ()) {
        var uri = "";
        if(withID != ""){
          uri = "\test\withID"
        }

        
        else {
            uri = "\test"
        }
        
        let method = GET
        let urlString = "https:myownURL\(uri)"
        
//generates a header
        let urlHeader=headersGenerator()

        URLSession.shared.dataTask(with: urlHeader) { [self] (data, response , error) in
            guard let data = data else { return }
            print(String(data: data, encoding: .utf8) ?? "Invalid JSON")

            do {
               let results = try JSONDecoder().decode(Results.self,from: data)
           
             completion(.success(results.userInfo))
            } catch {
             print("Error:\(error)")
          

            }
        }.resume()
    }

Model is as follows

struct Results: Codable {
    let userInfo:[ResultItem]
}

struct ResultItem: Codable, Identifiable {
    let id = UUID()
    let userId: String
    var userlastname:String
    var username:String
}

This is giving me a proper response as below when I dont pass withID(the url will be https:myownURL.test )

The output is as below

{"userInfo":[{"userId":"0390","userlastname":"test1","username":"test1"},{"userId":"0391","userlastname":"test2","username":"test2"},{"userId":"0392","userlastname":"test3","username":"test3"}]}

But if i run the url with withID(the url will be https:myownURL.test.withID )
the output should give single value, and I am getting a single value but the format if different

{"userId":"0390","userlastname":"test1","username":"test1"}

but the model is same for both API so that it should return response as below

{"userInfo":[{"userId":"0390","userlastname":"test1","username":"test1"}]}

please let me know what mistake I am doing so that the response will come like this

{"userInfo":[{"userId":"0390","userlastname":"test1","username":"test1"}]}

I have provided complete reference code which I am using with proper URL and data, please help me on this

As you tell the API what result you want with the withID variable you can decode the data conditionally.

And it's recommended to call the failure case of completion on any error you get.

func getUsers(completion: @escaping (Result<[ResultItem],Error>) -> ()) {
    var uri = "\test"
    if !withID.isEmpty {
        uri += "\withID"
    } 
    
    let method = GET
    let urlString = "https:myownURL\(uri)"
    
    //generates a header
    let urlHeader = headersGenerator()
    
    URLSession.shared.dataTask(with: urlHeader) { (data, _ , error) in
        if let error { completion(.failure(error)); return }
        print(String(data: data!, encoding: .utf8) ?? "Invalid JSON")
        do {
            if !withID.isEmpty {
                let results = try JSONDecoder().decode(ResultItem.self,from: data!)
                completion(.success([results]))
            } else {
                let results = try JSONDecoder().decode(Results.self,from: data!)
                completion(.success(results.userInfo))
            }
        } catch {
            completion(.failure(error))
        }
    }.resume()
}