NSViewController.ViewLoading
A property wrapper that loads the view controller’s view before accessing the property.
Declaration
@propertyWrapper struct ViewLoading<Value>Overview
Use this property wrapper on view controller properties that can be nil before the view controller’s view loads. Wrapping view controller properties this way eliminates crashes that can occur from implicitly defining properties as Optional, and then referencing them before the view controller finishes loading.
The following example uses the NSViewController.ViewLoading wrapper to ensure that dateLabel NSTextField loads before referencing it in the didSet of the date property observer:
class DateViewController: NSViewController {
@ViewLoading 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, the system can safely access and set the date property.
let dateViewController = DateViewController()
dateViewController.date = Date()Use this property wrapper over implicitly unwrapped optionals for IBOutlets as well.
@IBOutlet @ViewLoading private var dateLabel: NSTextField