Why don’t Swift classes have a memberwise initializer?
Updated for Xcode 12.5
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.
SPONSORED Emerge helps iOS devs write better, smaller apps by profiling binary size on each pull request and surfacing insights and suggestions. Companies using Emerge have reduced the size of their apps by up to 50% in just the first day. Built by a team with years of experience reducing app size at Airbnb.
Sponsor Hacking with Swift and reach the world's largest Swift community!
