在Swift中解析时未从JSON获得响应

这是我的JSON结构和postman的响应

{
"jsonrpc": "2.0",
"result": {
"categories": [
    {
        "id": 91,
        "title": "ADMINISTRATION & SECRETARIAL",
    },
    {
        "id": 62,
        "title": "BEAUTY",
    },
    {
        "id": 325,
        "title": "CARE",

对于上述响应，我创建了如下模型:

struct CategoryModel: Codable {
let jsonrpc: String?
let result: ResultCat?
}
struct ResultCat: Codable {
let categories: [Categorymine]?
}
struct Categorymine: Codable {
let id: Int?
let title, slug: String?
}

*APIRestManager中的代码:我在这里进行了通用可编码服务调用，在这里我得到了响应，但在viewcontroller中使用此服务调用时，我没有得到响应，为什么？我哪里错了

import Foundation
import Alamofire

class GeneralResponse<T: Codable>: Codable {
var jsonrpc: String
var result: T?
}

struct RequestObject {
var method: HTTPMethod
var path: String
var token: String?
var params: [String: Any]?
}

class WebService {

private let decoder: JSONDecoder
public init(_ decoder: JSONDecoder = JSONDecoder()) {
    self.decoder = decoder
}

public func serviceCall<T: Codable>(_ objectType: T.Type,
                                    with request: RequestObject,
                                    completion: @escaping  (T?, Error?) -> Void)  {

var headerParams: HTTPHeaders?

    AF.request(request.path, method: request.method, parameters: request.params,encoding: JSONEncoding.default, headers: headerParams)
        .responseJSON { response in

            switch response.result {
            case .success(let dictData):
                let JSON = dictData as? [String : Any]

                do {
                    let data = response.data
                    let responseData  = try self.decoder.decode(T.self, from: data ?? Data())
                    print("model data \(String(describing: responseData))")

                } catch {
                    completion(nil, error)
                }
            case .failure(let error):
                let error = error
                print(error.localizedDescription)
            }
        }
}
}

*viewcontroller中的代码:我正在使用下面的服务调用.这里的断点不在WebService()内.serviceCall(CategoryModel.self，with:request){(response，error)在中，我没有得到响应，为什么？，

note: i need entire CategoryModel response.

请引导我

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

var catData: CategoryModel? {
    didSet {}
}
override func viewDidLoad() {
    super.viewDidLoad()

    genericCall()
}

func genericCall(){

let request = RequestObject(method: .get, path: "https://testtt.com/dev/api/get-category", params: nil)

WebService().serviceCall(CategoryModel.self, with: request) { (response, error) in

    print("only response in vc \(response)")
    if let items = response {
        DispatchQueue.main.sync {
            self.catData = items
            self.tableView.reloadData()
        }
    }
    else{
        print(error)
    }
}
}
}