Changing allowsCellularAccess on existing NSURLSession

Question

Is it possible to change the value for allowsCellularAccess on an existing NSURLSession by modifying the underlying NSURLSessionConfiguration?

I want to honor any changes in a user's settings for my application without cancelling existing requests if their device is currently connected to WiFi.

Answer 1

No. A session copies its configuration. It does not retain it. What I would do in your situation is:

• Make a copy of the session's existing configuration and change that flag.
• Create a new session with the modified configuration.
• If the user is on Wi-Fi, call finishTasksAndInvalidate on the old session. This will keep the session around long enough to finish any existing requests, after which it will go away.
• If the user is on cellular, call invalidateAndCancel, then wait to restart those tasks until the user is on Wi-Fi.

Additionally, you may be able to call cancelByProducingResumeData: on a task, and then recreate (resume) it in a different session with a different configuration. The task will still report its original configuration for allowsCellularAccess, but will behave according to the configuration of the new session. (The stale reporting might be considered a bug.)