Final classes

Although class inheritance is very useful – and in fact large parts of Apple’s platforms require you to use it – sometimes you want to disallow other developers from building their own class based on yours.

Swift gives us a final keyword just for this purpose: when you declare a class as being final, no other class can inherit from it. This means they can’t override your methods in order to change your behavior – they need to use your class the way it was written.

To make a class final just put the final keyword before it, like this:

final class Dog {
    var name: String
    var breed: String

    init(name: String, breed: String) {
        self.name = name
        self.breed = breed
    }
}

SPONSORED Building and maintaining in-app subscription infrastructure is hard. Luckily there's a better way. With RevenueCat, you can implement subscriptions for your app in hours, not months, so you can get back to building your app.

Try it for free

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