Retain cycles

RetainCycle.swift

class ViewManager {
    var completion: (() -> Void)?

    func setup(completion: @escaping () -> Void) {
        self.completion = completion
    }
}

class ViewController: UIViewController {
    let nameLabel = UILabel()

    var manager = ViewManager()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        /* Setup nameLabel, etc - assume it's done sensibly */
    }
    
    override func viewWillAppear() {
        self.function1()
    }
    
    func function1() {
        manager.setup {
            self.nameLabel.frame.origin.x += 100
        }
    }
    
    func function2() {
        manager.setup { [weak self] in
            self?.nameLabel.frame.origin.x += 100
        }
    }
    
    func function3() {
        manager.setup { [unowned self] in
            self.nameLabel.frame.origin.x += 100
        }
    }   
}