nested-closure4.swift

class ViewControllerB: UIViewController {
    
    var workItem: DispatchWorkItem?
    
    override func viewDidLoad() {
        let view = self.view
        let workItem = DispatchWorkItem {
            UIView.animate(withDuration: 1.0) { [weak self] in // this leaks
                view?.backgroundColor = .red
            }
        }
        self.workItem = workItem
    }
}