Is it possible for multiple event processing cycles to work simultaneously in one application?

In iOS applications, a single main event loop (run loop) is usually used, which manages user interface events and system events. However, technically, it is possible to create and run multiple event loops in different threads, for example, to handle background tasks.

But it is important to understand that the main loop (main run loop) must be singular and run in the main thread, as it is responsible for updating the UI. Additional run loops can be used in worker threads to handle tasks, timers, or event sources.

Example of creating and starting a run loop in a background thread:

let thread = Thread {
    let runLoop = RunLoop.current
    runLoop.add(Port(), forMode: .default)
    runLoop.run()
}
thread.start()

Thus, simultaneous operation of multiple event loops is possible, but the main loop must be singular, and additional ones should be in separate threads for specific tasks.