[swift-evolution] [Draft] Mixins

Антон Жилин antonyzhilin at gmail.com
Mon Feb 29 12:51:16 CST 2016

I'm prepairing to create a pull request, so I moved the proposal from Gist
to my fork of swift-evolution.
Link to the proposal new and hopefully final home:

Should I create a pull request right now or wait a bit?

Some details need to be discussed:

1. Do mixins need associated types? Would generics be more appropriate to

2. `mixin` vs `mixin protocol`. On one hand, `mixin protocol` does not
require a keyword.
On the other hand, as stated in a special section, mixins cannot be used
everywhere a protocol can. Protocols, mixins, traits, interfaces are all
different entities.

3. `mixin` vs `trait`. Please read Wiki or any other source and tell what
is a better name.

4. Objective-C interfacing. Do we have to require it now? (I doubt so.) Can
we allow mixing-in Swift mixins to Objective-C classes?

5. Are you happy with Initializers section?

6. Can motivation examples be improved?

2016-02-29 4:07 GMT+03:00 Step C <schristopher at bignerdranch.com>:

> Sorry, I understood "that phrase" to mean what I just stated.
> On Feb 28, 2016, at 8:03 PM, Step C <schristopher at bignerdranch.com> wrote:
> I understood him to mean that abstract classes cannot be used for value
> types, but it would be natural to want that functionality. Mixins would
> provide that capability for value types as well as classes.
> On Feb 28, 2016, at 7:41 PM, Trent Nadeau <tanadeau at gmail.com> wrote:
> The quoted portion of the proposal below doesn't make any sense to me.
> Subclasses can't be value types. Do you mean the structs could have similar
> functionality?
> Firstly, only classes can inherit from such abstract classes, while it can
> be easily seen that some subclasses ofCachingSerializable or SignalSender would
> naturally have value semantics (be structs, in other words).
> On Sun, Feb 28, 2016 at 5:03 PM, Антон Жилин <swift-evolution at swift.org>
> wrote:
>> Link to the proposal: https://gist.github.com/Anton3/f0550922c1be0fc5447c
>> 2016-02-29 0:56 GMT+03:00 Step C <schristopher at bignerdranch.com>:
>>> It would be helpful if you include the new draft. Or at least a link to
>>> it.
>>> > On Feb 28, 2016, at 3:30 PM, Антон Жилин via swift-evolution <
>>> swift-evolution at swift.org> wrote:
>>> >
>>> > I have rewritten almost the whole proposal in the last 10 hours. I
>>> encourage everyone interested to reread it and suggest fixes, improvements,
>>> as well as new directions for discussion.
>>> > _______________________________________________
>>> > swift-evolution mailing list
>>> > swift-evolution at swift.org
>>> > https://lists.swift.org/mailman/listinfo/swift-evolution
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
> --
> Trent Nadeau
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