[swift-evolution] Public classes with private superclass

Tino Heth 2th at gmx.de
Tue Jul 5 05:03:54 CDT 2016

> How would this look in the exported API? Would it simply show itself as not inheriting from anything? If your base class inherited from something (e.g. NSObject), would the public subclasses show themselves as direct subclasses of that superclass (NSObject)?
I wouldn't care, but the last option sounds sensible (although I hope I'll never have to directly subclass NSObject in the future ;-)

> IMHO these things can be solved by private protocols with default implementation to reuse the code:
Not everything can be solved with protocols (stored properties, anyone?)

> Or you can just create a private class and use its instance in your classes:
> internal class MyClassImplementation {
> 	/// Implement shared code
> }
> public class MyClass {
> 	private var _impl = MyClassImplementation()
> }
> Which is fairly common solution.
Those six lines are written easily, but they don't do anything, so you have to add tons of boilerplate to do forwarding — and you destroy the internal class hierarchy.
Do you see a problem with "internal init"?

> Anyway, this is definitely out of scope of Swift 3 and as has been pointed out several times in the past month here, all discussions here should now focus on Swift 3 features.
Sorry, I've been busy with other things lately…
I know that anything that breaks compatibility with existing source has top priority now, and that there most likely won't be any resources to integrate stuff that doesn't fulfill that criterion — but has there been an actual announcement that no discussions about purely additive changes should be started at all?

Best regards,

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