Which component manages the execution flow inside the ViewController?

In iOS, within a ViewController, thread management is usually carried out using the main (primary) thread and additional threads, which can be created via GCD (Grand Central Dispatch) or OperationQueue.

The ViewController itself runs on the main thread, which is responsible for updating the UI. For executing background tasks, GCD or OperationQueue are used, which manage threads and task queues.

Example of using GCD inside a ViewController:

DispatchQueue.global(qos: .background).async {
    // Background task
    let data = fetchData()
    DispatchQueue.main.async {
        // UI update on the main thread
        self.updateUI(with: data)
    }
}

Thus, thread management within a ViewController is implemented through system components GCD and OperationQueue.