Why does Swift have both classes and structs?
Updated for Xcode 15
Classes and structs give Swift developers the ability to create custom, complex types with properties and methods, but they have five important differences:
- Classes do not come with synthesized memberwise initializers.
- One class can be built upon (“inherit from”) another class, gaining its properties and methods.
- Copies of structs are always unique, whereas copies of classes actually point to the same shared data.
- Classes have deinitializers, which are methods that are called when an instance of the class is destroyed, but structs do not.
- Variable properties in constant classes can be modified freely, but variable properties in constant structs cannot.
I’ll explain these differences in more detail soon, but the point is that they exist and that they matter. Most Swift developers prefer to use structs rather than classes when possible, which means when you choose a class over a struct you’re doing so because you want one of the above behaviors.
TAKE YOUR SKILLS TO THE NEXT LEVEL If you like Hacking with Swift, you'll love Hacking with Swift+ – it's my premium service where you can learn advanced Swift and SwiftUI, functional programming, algorithms, and more. Plus it comes with stacks of benefits, including monthly live streams, downloadable projects, a 20% discount on all books, and free gifts!
Sponsor Hacking with Swift and reach the world's largest Swift community!
