Notice: Undefined index: understanding-swift in /var/sites/hackingwithswift.com/site/src/Controller/NewBooksReadController.php on line 89
Why don’t Swift classes have a memberwise initializer? - a free tutorial

NEW: Subscribe to Hacking with Swift+ and accelerate your learning! >>

Why don’t Swift classes have a memberwise initializer?

Paul Hudson    @twostraws   

One of the many useful features of Swift’s struct is that they come with a synthesized memberwise initializer, letting us create new instances of the struct just by specifying its properties. However, Swift’s classes don’t have this feature, which is annoying – but why don’t they have it?

The main reason is that classes have inheritance, which would make memberwise initializers difficult to work with. Think about it: if I built a class that you inherited from, then added some properties to my class later on, your code would break – all those places you relied on my memberwise initializer would suddenly no longer work.

So, Swift has a simple solution: rather than automatically generating a memberwise initializer, authors of classes must write their own initializer by hand. This way, you can add properties as much as you want without affecting the initializer for your class, and affecting others who inherit from your class. And when you do decide to change your initializer, you’re doing yourself, and are therefore fully aware of the implications for any inheriting classes.

Hacking with Swift is sponsored by Instabug

SPONSORED Are you tired of wasting time debugging your Swift app? Instabug’s SDK is here to help you minimize debugging time by providing you with complete device details, network logs, and reproduction steps with every bug report. All data is attached automatically, and it only takes a line of code to setup. Start your free trial now and get 3 months off exclusively for the Hacking with Swift Community.

Start your free trial!

Sponsor Hacking with Swift and reach the world's largest Swift community!

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Link copied to your pasteboard.