The Lazy Variables: What and Why in Swift

lazy var innit (not init)

Photo by Holger Link on Unsplash

This article covers lazy variables, why you might use them and how they are used in Swift.

Difficulty: Beginner | Easy | Normal | Challenging

Prerequisites:

• Be able to code Swift using Playgrounds
• Some knowledge of closures would be useful

Terminology

closure: A self-contained block of functionality that can be passed around

lazy variables: A technique in that a property is only created when it is needed

Motivation

I recently completed a rather fantastic date manager in Swift, that creates the dateFormatter as a lazy var.

private lazy var dateFormatter: DateFormatter = {
    let dateFormatter = DateFormatter()
    dateFormatter.locale = Locale.current
    return dateFormatter
}()

The way this closure works is interesting, and demands more attention than can be given in a couple of sentences.

So let us press on!

The step-by-step

Properties can be rather easily set up, for example here an optional name

var name: String?