Hands-On Design Patterns with Swift

Lazy initialization

In Objective-C, we may want to initialize some properties lazily as they may only be accessed at a future time, we don't want to block the init() call with a long-running operation, or when a required instance property will only be accessible at a later time.

In Swift, we are blessed by the presence of the lazy keyword.

Let's start with this code and see how we can improve it:

class MyView: NSView  {    let image: NSImage!    let imageView = NSImageView(frame: .zero)        init(imageName: NSImage.Name, frame: NSRect) {        image = NSImage(named: imageName)        super.init(frame: frame)    }    func setup() {        addSubview(imageView)        imageView.frame = bounds.insetBy(dx: 5.0, dy: 5.0)        imageView.image = image        imageView.imageAlignment = .alignCenter } ...