如果在完成之前退出页面，如何取消 URLSession.shared.dataTask？

Question

按照/sf/answers/1939869921/的建议，我可以执行异步下载，如下所示，并在viewDidLoad.

    func loadItems(tuple : (name : String, imageURL : URL)) {
        print("Download Started")
        URLSession.shared.dataTask(with: tuple.imageURL, completionHandler :
        { data, response, error in
            guard let data = data, error == nil else { return }
            print(response?.suggestedFilename ?? tuple.imageURL.lastPathComponent)
            print("Download Finished")
            DispatchQueue.main.async() { [weak self] in
                self?.displayFlag(data: data, title: tuple.name)
            }
        }).resume()
    }

这一切都运作良好。我的问题是，如果下载缓慢，并且我退出页面，如何以及在哪里（viewDidUnload？看起来已经不推荐使用）可以取消获取（图像下载）任务？

Answer 1

保存URLSessionTask参考：

private weak var task: URLSessionTask?

func loadItems(name: String, url: URL) {
    let task = URLSession.shared.dataTask(with: url) { [weak self] data, response, error in
        guard let data = data, error == nil else { return }
        print(response?.suggestedFilename ?? url.lastPathComponent)
        print("Download Finished")
        DispatchQueue.main.async {
            self?.displayFlag(data: data, title: name)
        }
    }
    task.resume()
    self.task = task
}

然后，当解雇时，cancel它：

deinit {
    task?.cancel()
}