Diffable.swift

import UIKit

typealias UserDataSource = UITableViewDiffableDataSource<UsersViewController.Section, User>
typealias UserSnapshot = NSDiffableDataSourceSnapshot<UsersViewController.Section, User>

class UsersViewController: UITableViewController {
    var users = [User]()
    var datasource: UserDataSource!
    
    func configureDataSource() {
        datasource =  UserDataSource(tableView: tableView) { (tableview, indexpath, user)
            -> UITableViewCell
            let cell = tableView.dequeuReusableCell(withIdentifier: "identifier", for: indexpath )
            cell.textLabel.text = user.name
            return cell
        }
    }
    
    func addNewUser(id: Int, name: String) {
        users.append(User(id: 1, name: "Steve"))
        createSnapshot(users)
    }
    
    func createSnapshot(_ users: [User]) {
        let snapshot = UserSnapshot()
        snapshot.appendSections([.main])
        snapshot.appendItems(users)
        datasource.apply(snapshot, animatingDifference: true)
    }
}

extension UsersViewController {
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        //based on your datasource (hashable) diffable will be able to lookup user using indexpath.
        guard let user = datasource.itemIdentifier(for: indexPath) else {
            return
        }
        print(user.name)
    }
}

extension UsersViewController {
    fileprivate enum Section {
        case main
    }
}