How can I cancel the URLSession.shared.dataTask if I exit the page before it completes?

Question

Following the recommendation from https://stackoverflow.com/a/27712427/3286489, I can perform asynchronous download as below, and it is called during 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()
    }

This all works well. My question is, in the event of a slow download, and I exit the page, how and where (viewDidUnload? looks that that is deprecated already) can I cancel the fetching (image downloading) task?

Answer 1

Save the URLSessionTask reference:

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
}

Then, when dismissing, cancel it:

deinit {
    task?.cancel()
}