How to find and cancel a task in NSURLSession?

Question

I'm using an NSURLSession object to load images in my application. That could be loading several images simultaneously.

In some moments I need to cancel the loading of one specific image and continue loading others.

Could you suggest the correct way to do that?

Answer 1

To get tasks list you can use NSURLSession's method

- (void)getTasksWithCompletionHandler:(void (^)(NSArray *dataTasks, NSArray *uploadTasks, NSArray *downloadTasks))completionHandler;

Asynchronously calls a completion callback with all outstanding data, upload, and download tasks in a session.

Then check task.originalRequest.URL for returned tasks to find the one you want to cancel.

Answer 2

Based on all the answers below, I'd go for something like this:

Swift 5

 func cancelTaskWithUrl(_ url: URL) {
    URLSession.shared.getAllTasks { tasks in
      tasks
        .filter { $0.state == .running }
        .filter { $0.originalRequest?.url == url }.first?
        .cancel()
    }
  }

You also probably want to account for your task completion handler, since canceling the task will result Error in that completion handler.