如何在TableViewController中预取单元格？

Question

我阅读了有关预取的信息，并添加了委托，数据源和所需的两个函数，现在，我需要在这两个函数中添加什么？这是用来实现60 fps平滑滚动的吗？

很抱歉，如果这个问题含糊不清。

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.dataSource = self
        tableView.prefetchDataSource = self

        let userJSONURLString = "https://qapital-ios-testtask.herokuapp.com/users"
        let activitiesJSONURLString = "https://qapital-ios-testtask.herokuapp.com/activities?from=2016-05-23T00:00:00+00:00&to=2019-05-23T00:00:00+00:00"
        guard let userURL = URL(string: userJSONURLString) else { return }
        guard let activitiesURL = URL(string: activitiesJSONURLString) else { return }

        URLSession.shared.dataTask(with: activitiesURL) { (data, response, err) in
            guard let data = data else { return }
            do {
                // Activities
                let decoder = JSONDecoder()
                decoder.dateDecodingStrategy = .iso8601
                let result = try decoder.decode(Root.self, from: data)
                self.activities = result.activities

                URLSession.shared.dataTask(with: userURL) { (data, response, err) in
                    guard let data = data else { return }
                    do {
                        // Users
                        let usersJson = try JSONSerialization.jsonObject(with: data, options: [])
                        guard let jsonArray = usersJson as? [[String: Any]] else { return }

                        for dic in jsonArray {
                            guard let avatarUrl = dic["avatarUrl"] as? String else { return }
                        }

                    } catch {
                        print("Error serializing json: ", error)
                    }
                    }.resume()
            } catch {
                print("Error serializing json: ", error)
            }

            DispatchQueue.main.async {
                self.tableView.reloadData()
            }
        }.resume()
    }

    func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath]) {
        print("prefetching row of \(indexPaths)")
    }

    func tableView(_ tableView: UITableView, cancelPrefetchingForRowsAt indexPaths: [IndexPath]) {
        print("cancel prefetch row of \(indexPaths)")
    }
}