Describe a scenario where your application performs background tasks and how it is implemented.

An iOS application can perform tasks in the background, such as content downloads, data updates, or audio playback, when the user is inactive or the app is minimized.

The following mechanisms are used to implement background tasks:

• Background Modes: Enabling relevant modes in Capabilities (e.g., audio, location, VoIP).
• Background Fetch: Allows the system to periodically launch the app to update content.
• NSURLSession with backgroundConfiguration: For uploading or downloading files in the background, even if the app is closed.
• Background Tasks (BGTaskScheduler): Allows scheduling tasks to be executed by the system at optimal times.

Example of using NSURLSession for background download:

let config = URLSessionConfiguration.background(withIdentifier: "com.example.app.bgSession")
let session = URLSession(configuration: config, delegate: self, delegateQueue: nil)

if let url = URL(string: "https://example.com/file.zip") {
    let task = session.downloadTask(with: url)
    task.resume()
}

Thus, the app can continue downloading a file even if the user minimizes the app or it has been unloaded from memory.