How to implement background downloading of large files using URLSession in iOS applications?
Handling network requests in the background is critical for a quality user experience, especially when transferring large files. If the user minimizes the app or the system terminates it to free up resources, a regular download task will be interrupted. To prevent this, a special background session configuration is used.
Creating such a session requires using the background configuration method with a unique string identifier. This identifier allows the operating system to associate the download process with your app even after it has been completely restarted. It is important to initialize this session object immediately upon app launch so the system can timely delegate task completion events to it.
The setup process includes the following mandatory steps:
When the system finishes downloading in the background, it calls the app delegate method, passing the saved session identifier. The app briefly resumes in the background so you can move the downloaded file from the temporary directory to permanent storage. Upon completing all operations, a special completion handler must be called to inform the system about the successful data processing.