Lazy.swift

class AppContext {
  
  let device : UIDevice
  
  // Delay object creation
  lazy var dataService: DataService = DataService()
  
  // Property is depended on other parts of a class, that aren’t available yet
  lazy var isTablet: Bool = { [unowned self] in
    self.device.userInterfaceIdiom == .Pad
  }()

  init (device: UIDevice) {
    self.device = device
  }
}