# NSWindowController.WindowLoading A property wrapper that loads the receiver’s window. ``` @propertyWrapper struct WindowLoading ``` ## Overview Use this property wrapper on window controller properties that can be `nil` before the window controller’s window loads. Wrapping window controller properties this way eliminates crashes that can occur from implicitly defining properties as , and then referencing them before the window controller finishes loading. The following example uses the `NSWindowController.WindowLoading` property wrapper to ensure that `dateLabel` [`NSTextField`](/documentation/AppKit/NSTextField) loads before referencing it in the `didSet` of the `date` property observer: ```swift class DateWindowController: NSWindowController { @WindowLoading private var dateLabel: NSTextField var date: Date? { didSet { let dateFormatter = DateFormatter() dateFormatter.dateStyle = .full let dateString = dateFormatter.string(from: self.date ?? Date()) self.dateLabel.stringValue = dateString } } } ``` After loading [`NSTextField`](/documentation/AppKit/NSTextField), the system can safely access and set the `date` property. ```swift let dateWindowController = DateWindowController() dateWindowController.date = Date() ``` Use this property wrapper over implicitly unwrapped optionals for `IBOutlets` as well. ```swift @IBOutlet @WindowLoading private var dateLabel: NSTextField ``` ## Topics ### Creating a WindowLoading Property Wrapper [`init()`](/documentation/AppKit/NSWindowController/WindowLoading/init()) Creates an empty property wrapper that loads the window controller’s window before accessing the property. [`init(wrappedValue:)`](/documentation/AppKit/NSWindowController/WindowLoading/init(wrappedValue:)) Creates a property wrapper that loads the window controller’s window before accessing the property. ## See Also [`NSViewController.ViewLoading`](/documentation/AppKit/NSViewController/ViewLoading) A property wrapper that loads the view controller’s view before accessing the property. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)