[swift-evolution] [Review] SE-0022: Referencing the Objective-C selector of a method

Douglas Gregor dgregor at apple.com
Wed Jan 20 17:48:11 CST 2016


> On Jan 19, 2016, at 4:52 PM, Douglas Gregor via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
>> On Jan 19, 2016, at 4:40 PM, Jacob Bandes-Storch <jtbandes at gmail.com <mailto:jtbandes at gmail.com>> wrote:
>> 
>> Is there a well-defined meaning for `#` ?
> 
> Not yet.
> 
>> What about #selector(x)?
> 
> Objective-C selector formation is a *very* narrow feature to consider stealing one of our few underused sigils.

Actually, this isn’t that much different from “#available”, in the sense that it’s a special, compiler-supported expression type for which we don’t want to necessarily steal a keyword. What do others think about “#selector”?

	- Doug


> 	- Doug
> 
>> 
>> On Tue, Jan 19, 2016 at 4:36 PM, Douglas Gregor <dgregor at apple.com <mailto:dgregor at apple.com>> wrote:
>> 
>>> On Jan 19, 2016, at 4:33 PM, Jacob Bandes-Storch <jtbandes at gmail.com <mailto:jtbandes at gmail.com>> wrote:
>>> 
>>> I'm fine with objc_selector(x.foo) or
>> 
>> 
>>> @selector(x.foo).
>> 
>> @selector is a no-go: @ means “attribute” in Swift.
>> 
>>>  x.foo.selector  is cute, but wouldn't this clash with property getters/setters?
>> 
>> It would only be available on values of function type that refer to @objc methods or initializers. We would (still) need a different mechanism to get at the selectors of getters or setters; SE-0022 didn’t solve this problem either.
>> 
>> 	- Doug
>> 
>>> 
>>> Jacob
>>> 
>>> On Tue, Jan 19, 2016 at 4:21 PM, Douglas Gregor via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>>> On Jan 19, 2016, at 2:46 PM, David Hart <david at hartbit.com <mailto:david at hartbit.com>> wrote:
>>>> 
>>>> What effect would that have? Would the options still return a type (Selector) that is CustomStringConvertible or would it just be compiler magic?
>>> 
>>> Either way, we’ll return a Selector. The concern about “Selector(x.foo)” is that we would need special, ad hoc overload-resolution rules to decide between this magic syntax and other initializers of Selector. Making it a separate expression (“objc_selector(x.foo)”) or a special property on values of function type (“x.foo.selector”) eliminate that issue.
>>> 
>>> We’d love to hear everyone’s thoughts on those approaches.
>>> 
>>> 	- Doug
>>> 
>>>> David.
>>>> 
>>>>> On 19 Jan 2016, at 23:43, Joe Groff via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>>> 
>>>>> We discussed this proposal during our core team review meeting, and concerns were raised about the implementability of the proposed 'Selector(Type.method)' syntax. Producing the selector is something that can't quite be modeled as a real initializer, so the type checker would have to perform heroics to disambiguate a selector literal reference from a proper initializer call. We recommend reconsidering alternative syntactic forms for referencing the selector. Potential options include:
>>>>> 
>>>>> - A unique prefix identifier, such as `objc_selector(Type.method)`, as you had originally proposed, or
>>>>> - Taking advantage of the fact that functions don't have members to ascribe special behavior to 'Type.method.objcSelector', or something like it.
>>>>> 
>>>>> -Joe
>>>>> 
>>>>>> On Jan 18, 2016, at 8:02 AM, Joe Groff via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>>>> 
>>>>>> Hello Swift community,
>>>>>> 
>>>>>> The review of “Referencing the Objective-C selector of a method” begins now and runs through January 23, 2016. The proposal is available here:
>>>>>> 
>>>>>> 	https://github.com/apple/swift-evolution/blob/master/proposals/0022-objc-selectors.md <https://github.com/apple/swift-evolution/blob/master/proposals/0022-objc-selectors.md>
>>>>>> 
>>>>>> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at
>>>>>> 
>>>>>> 	https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>>>>> 
>>>>>> or, if you would like to keep your feedback private, directly to the review manager.
>>>>>> 
>>>>>> What goes into a review?
>>>>>> 
>>>>>> The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:
>>>>>> 
>>>>>> 
>>>>>> 	• What is your evaluation of the proposal?
>>>>>> 	• Is the problem being addressed significant enough to warrant a change to Swift?
>>>>>> 	• Does this proposal fit well with the feel and direction of Swift?
>>>>>> 	• If you have you used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
>>>>>> 	• How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
>>>>>> More information about the Swift evolution process is available at
>>>>>> 
>>>>>> 	https://github.com/apple/swift-evolution/blob/master/process.md <https://github.com/apple/swift-evolution/blob/master/process.md>
>>>>>> 
>>>>>> Thank you,
>>>>>> 
>>>>>> -Joe
>>>>>> 
>>>>>> Review Manager
>>>>>> 
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>>>>> 
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