What are the different URLSessionConfiguration options?

Sources & Resources

Main Source: 🔗 Ace the iOS Interview

Additional Sources:

Further Reading:

TL/DR

URLSession is the main object responsible for managing HTTP & HTTPS requests in iOS.

In order to create a URLSession, we need to initialize it with a URLSessionConfiguration type:

URLSession(configuration: .default)

The default URLSessionConfiguration uses a persistent disk-based cache and stores credentials in the user’s keychain.

Next, we have the ephemeral URLSessionConfiguration type.

URLSession(configuration: .ephemeral)

It’s similar to the default configuration, however it doesn’t maintain a cache, store credentials, or save any session-related data to disk. Hence, the name “ephemeral”.

Instead, all session-related data is stored in RAM. The only time an ephemeral session writes data to disk is when you explicitly instruct it to write the contents of a URL to a file.

Finally, we have the background configuration type:

URLSession(configuration: .background(withIdentifier: "IDENTIFIER_NAME"))

This creates a URLSessionConfiguration object that allows HTTP and HTTPS uploads or downloads to be performed in the background. This configuration is most commonly used when transferring data files while the app runs in the background.

A URLSession configured with this type hands controlof the transfer over to the system which then handles the file transfer in a separate process. In iOS, this configuration makes it possible for transfers to continue even when the app is suspended or terminated.