strong_reference_cycle_closure.swift

// MARK: - Strong reference cycle for closures
class ViewController: UIViewController {
    
    lazy var loginCompletion: (Bool) -> Void = { success in // <- place where we has been mistaken. It must be resolved using capture list with 'unowned' reference
        if success {
            self.navigationController?.popToRootViewController(animated: true)
        }
    }
    
    deinit {
        print("ViewController was deinitialized")
    }
    
}

var viewController: ViewController? = ViewController()
viewController!.loginCompletion

viewController = nil
/*
 !!! This is strong reference cycle for closure. !!!

 We have memory leak now!
 */

/*
 Solution after fixes
 */

// MARK: - Resolve strong reference cycle using closure capture list
class ViewController: UIViewController {
    
    lazy var loginCompletion: (Bool) -> Void = { [weak self] success in // We resolve memary leak just adding [weak self]
        if let `self` = self, success {
            self.navigationController?.popToRootViewController(animated: true)
        }
    }
    
    deinit {
        print("ViewController was deitialized")
    }
    
}

var viewController: ViewController? = ViewController()
viewController!.loginCompletion

viewController = nil
/*
 print: ViewController was deinitialized
 */