> What is your evaluation of the proposal?
+1
> Is the problem being addressed significant enough to warrant a change to
> Swift?
Yes
> Does this proposal fit well with the feel and direction of Swift?
Yes
> If you have used other languages or libraries with a similar feature, how do
> you feel that this proposal compares to those?
Lots of languages have key-paths, but usually they are strings. This adds some
type-safety, so that’s nice.
> How much effort did you put into your review? A glance, a quick reading, or
> an in-depth study?
A quick reading. I also have a couple of questions:
1) Can we get keypaths from protocol existentials?
protocol MyProto {
var something: Int { get }
}
struct MyThing: MyProto { /* … */ }
let myProtoSomethingKeypath = #keypath(MyProto, .something)
let value: Int = MyThing()[keypath: myProtoSomethingKeypath] // seems
reasonable, right?
2) What about if it has associated types?
let secondElement = #keypath(Collection, .subscript[1]) // if
Collection.Iterator.Element had constraints, could we dig in to the instance?
let _: Int = [1,2,3][keypath: secondElement]
let _: String = [“a”, “b”, “c”][keypath: secondElement]
But I’d still +1 the proposal even if was limited to concrete types.
Also, that brings me to 2 related comments regarding the evolution of the
feature:
1) It would be nice to allow keypaths of constrained protocol existentials
let secondElementFirstCharacter = #keypath(Collection where
Iterator.Element == String, .subscript[0].characters.first)
2) It would be nice to be able to get keypaths to members which we don’t know
exist. Members and protocol conformances may be retroactively added by
3rd-party code.
And that’s all.
- Karl
> On 30 Mar 2017, at 18:25, Douglas Gregor via swift-evolution
> <[email protected]> wrote:
>
> Hello Swift community,
>
> The review of SE-0161 "Smart KeyPaths: Better Key-Value Coding for Swift"
> begins now and runs through April 5, 2017. The proposal is available here:
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0161-key-paths.md
>
> <https://github.com/apple/swift-evolution/blob/master/proposals/0161-key-paths.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. When replying, please try to keep the proposal link at the top of
> the message:
>
> Proposal link:
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0161-key-paths.md
>
> <https://github.com/apple/swift-evolution/blob/master/proposals/0161-key-paths.md>
> Reply text
> Other replies
>
> <https://github.com/apple/swift-evolution/pulls#what-goes-into-a-review-1>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 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,
>
> -Doug
>
> Review Manager
>
> _______________________________________________
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