How to deep copy data from completionHandler clousure to ViewController class in Swift?

Question

I've tried to DeepCopy data with NSCopying protocol and with JSON decoder/encoder, but everytime I stumble upon somewhere and can't get it fixxed.

How can I copy exactly the same all of the contents from result to class variable postData? I'd like to add it to tableview programaticly but I just can't get it to work.

Here is ViewController class code:

class ViewController: UIViewController {
       
    
    var postData:[Post] = []
    let tableView = UITableView()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        
        DataLoader.shared.fetchPostData(completionHandler: {
            result in
            //it prints result here
            for x in result{
                print(x.id!)
            }
            
            self.postData = result
            
        })
        
        //I'd like to print it here
        for x in self.postData{
            print(x.id!)
        }
    }

Here is Post class code:

import Foundation

struct Post: Decodable{
    var userId: Int!
    var id: Int!
    var title: String!
    var body: String!
}

and here is DataLoader class code:

import Foundation


class DataLoader: Codable {
    
    //var classData:[Post] = []
    static let shared = DataLoader()
    
    func fetchPostData(completionHandler: @escaping ([Post]) -> Void){
        let url = URL(string: "https://jsonplaceholder.typicode.com/posts")!
        
        URLSession.shared.dataTask(with: url) {
            (data, response, error) in
            
            guard let data = data else { return }
        
        
        do {
            let postsData = try JSONDecoder().decode([Post].self, from: data)
            //self.classData = postsData
            completionHandler(postsData)
            
        }
        catch {
            let error = error
            print(error.localizedDescription)
            //completionHandler(nil)
        }
        }.resume()
    }
}