> On Apr 11, 2016, at 10:15 AM, Joe Groff <jgr...@apple.com> wrote:
>
>
>> On Apr 7, 2016, at 5:12 PM, Douglas Gregor via swift-evolution
>> <swift-evolution@swift.org> wrote:
>>
>> One could perhaps work around (a), (b), and (d) by allowing compound
>> (function-like) names like tableView(_:viewFor:row:) for properties, and
>> work around (c) by allowing a method to satisfy the requirement for a
>> read-only property, but at this point you’ve invented more language hacks
>> than the existing @objc-only optional requirements. So, I don’t think there
>> is a solution here.
>
> To me, compound names for closure properties and satisfying property
> requirements with methods aren't hacks, they're missing features we ought to
> support anyway. I strongly prefer implementing those over your proposed
> solution.
I haven’t seen these come up in any discussion that wasn’t about mapping
Objective-C optional requirements to something else in Swift. What other use
cases are you envisioning?
> It sounds to me like a lot of people using optional protocol requirements
> *want* the locality of control flow visible in the caller, for optimization
> or other purposes,
Most of the requests I see for this feature are of the form “this works for
@objc protocols, so it should work everywhere,” and most of the push-back I’ve
seen against removing ‘optional’ is a concern over interaction with Cocoa. I
haven’t gotten the sense that optional requirements are considered to be the
best design for any particular task in Swift.
> and your proposed solution makes this incredibly obscure and magical.
That’s fair. The mechanism I’m talking about *is* a bit hard to explain—we
would need to rely on the diagnostic for cases where one tries to call a method
that is caller-defaulted from Swift code, e.g.,
error: method ‘foo(bar:wibble:)’ may not be implemented by the adopting
class; add a default implementation via an extension to protocol ‘Foo'
This would only affect optional requirements of protocols imported from
Objective-C. My hypothesis is that those just aren’t used in Swift app code.
- Doug
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