[swift-evolution] [Proposal] Explicit Non-Default-Implemented Protocol Requirements

Taylor Swift kelvin13ma at gmail.com
Wed Aug 2 10:15:48 CDT 2017

I agree with this, extensions on types defined in the same file are
generally silly, and default implementations belong in the protocol body. I
don’t agree with certain style guides prescription of same-file extensions;
they should only be used to hide protocol conformances that are
“unimportant” to the functionality of the type. In practice this means only
conformances like CustomStringConvertible and CustomDebugStringConvertible
live in extensions.

If you want to group related methods, use linebreaks and whitespace for
that. Don’t split up the type braces since that messes up the whole
one-set-of-braces == one type definition visual rule.

The only time it ever makes sense to extend a non concrete type that you
own is when adding conditional default implementations. Having to extend a
bare protocol is the product of a language limitation.

On Wed, Aug 2, 2017 at 6:26 AM, Tino Heth via swift-evolution <
swift-evolution at swift.org> wrote:

> That would work as well, but it has the downside of forcing a potentially
> huge number of methods to be implemented in a single place, reducing the
> readability as opposed to packing them into semantically related groups in
> the form of extensions.
> I really don't get why people are so obsessed with same-file extensions:
> They are recommended in style guides, influencers blog about them, and
> they motivated a ridiculous complex change in the access rights system. Yet
> I haven't seen any evidence that they offer real benefit.
> Extensions are great for adding useful helpers to existing types, and
> still allow you to selectively expose details of your own classes — but
> most people seem to ignore those options and focus on something can be done
> better with plain old comments.
> [sorry for the rant — but I think a critical look at extensions is long
> overdue: I rarely see someone questioning their role, so basically, we are
> making important decisions based on pure superstition]
> A protocol itself is already a vehicle to group related methods, and if
> you have a huge entity, it doesn't get better just because you split it and
> hide its complexity.
> Also, please include the original message for reference purposes.
> [hopes Discourse will happen soon ;-) ]
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20170802/0517266d/attachment.html>

More information about the swift-evolution mailing list