Is it always necessary to use [unowned self] in closures in Swift?

Hi everyone! I started learning Swift and encountered a problem with memory management in closures. I've read many articles on Stack Overflow, and everywhere they say you need to use `[weak self]` or `[unowned self]` to avoid retain cycles. But I'm confused about when exactly to use `unowned`. Here's an example: I have a class `NetworkManager` that loads data and calls a closure upon completion. ```swift class NetworkManager { func fetchData(completion: @escaping (Data?) -> Void) { DispatchQueue.global().async { // simulate loading sleep(2) let data = Data() completion(data) } } } class ViewController: UIViewController { let networkManager = NetworkManager() func loadData() {