As an additive feature it's unlikely to be considered in the Swift 3 timeline anyway. You can search the list archive for previous discussion on lenses. I think David is saying that this proposal looks like it's asking for a special case where a more general solution might be appropriate. On Tue, Jun 28, 2016 at 6:11 PM Michael Peternell via swift-evolution < [email protected]> wrote:
> Really?? Or we just have #set and #get and no lenses, and it's done for > Swift 3? > > I never heard of lenses (Google does not help here). Was this serious or > were you joking? Unless you can explain why #set and #get without lenses > would be bad... or maybe #set and #get *are* lenses, in which case I'm not > sure what you were trying to say. Reflexion -> Reflection? > > -Michael > > > Am 29.06.2016 um 00:55 schrieb David Hart via swift-evolution < > [email protected]>: > > > > This looks like lenses. I think we need to wait until after Swift 3 to > discuss it, and come up with a bigger design that ties to reflexion. > > > >> On 28 Jun 2016, at 22:04, Michael Peternell via swift-evolution < > [email protected]> wrote: > >> > >> So you're proposing that `#set(aVariableName)` should translate to > `{aVariableName=$0}`, right? Where aVariableName can be any valid lvalue > like `self.users` or `users` or `vc.viewControllers`.. > >> > >> I think this would be a good extension to Swift. (`users.set` does not > work BTW, because maybe the `users` object has a `set` property.. maybe I > wanted to refer to the `set` property which also happens to refer to a > closure value.) > >> > >> `#set(aVariableName)` also feels consistent with the > `#keyPath(aVariableName)` property and falls into a similar category. Maybe > `#setter(aVariableName)` would be even more clear? Furthermore, I want to > additionally propose to introduce `#get(aVariableName)` (or > `#getter(aVariableName)`) too. > >> > >> -Michael > >> > >>> Am 28.06.2016 um 20:18 schrieb Austin Feight via swift-evolution < > [email protected]>: > >>> > >>> Proposal: > >>> > >>> I propose adding setter methods to vars, which could look something > like this: `ApiClient().fetchUsers().then(#set(users))` > >>> > >>> Initially I thought it should work like this: > `ApiClient().fetchUsers().then(users.set)` > >>> but to accomplish a line of code that flows grammatically, I believe > putting "set" where it would naturally fall if the code was being read as a > sentence is more Swifty. > >>> > >>> Rationale: > >>> > >>> The following code makes me smile: > >>> > >>> ApiClient().fetchUsers().then(displayUsers) > >>> > >>> It exemplifies the beauty of Swift. First-class functions make this > line of code read very well. Consider some alternatives: > >>> > >>> 1. ApiClient().fetchUsers().then { displayUsers($0) } > >>> 2. ApiClient().fetchUsers().then { users in displayUsers(users) } > >>> 3. ApiClient().fetchUsers().then { (users: [User]) in > displayUsers(users) } > >>> > >>> Using the lessons learned from Swift API Design Guidelines (WWDC 2016 > Session 403) having an emphasis on clarity, my analysis of the alternatives > is: > >>> > >>> 1. $0 adds no additional information as to the type or explanation of > what the argument is, thus adding nothing to the line of code for clarity, > and therefore should be omitted > >>> 2. adding "users" also adds nothing to the clarity of the code. The > function, properly, contains the information necessary to reason about the > argument it takes and what it does, and therefore adding "users" is > redundant > >>> 3. Not only is "users" redundant, but also is the explicit type label. > The `displayUsers` method will only accept one type of argument, so we're > duplicating information that the compiler (and autocomplete) already gives > us > >>> > >>> With this I conclude that > `ApiClient().fetchUsers().then(displayUsers)` is the Swiftiest option. > >>> I want to extend this same logic to when I find myself writing code > like this: > >>> > >>> ApiClient().fetchUsers().then { users in > >>> self.users = users > >>> } > >>> > >>> or alternatively, because "users" is likely redundant information > again, > >>> > >>> ApiClient().fetchUsers().then { self.users = $0 } > >>> > >>> Personally I steer clear of `$0` as much as possible, because I very > rarely feel that it provides the information necessary for code clarity. > But beyond that, this code no longer reads as nicely as the code we had > before. > >>> > >>> Whereas `ApiClient().fetchUsers().then(displayUsers)` flows nicely as > a sentence and reads grammatically, `ApiClient().fetchUsers().then { > self.users = $0 }` no longer does. > >>> > >>> I think this feature could have a simple implementation where the > compiler replaces `#set(X)` with `{ X = $0 }`, and I believe it would go a > long way with respect to code clarity, especially when X is something > longer like `self.view.bounds.origin.x` > >>> > >>> > >>> Looking forward to hearing thoughts from the community, > >>> Austin Feight > >>> _______________________________________________ > >>> swift-evolution mailing list > >>> [email protected] > >>> https://lists.swift.org/mailman/listinfo/swift-evolution > >> > >> _______________________________________________ > >> swift-evolution mailing list > >> [email protected] > >> https://lists.swift.org/mailman/listinfo/swift-evolution > > > > _______________________________________________ > > swift-evolution mailing list > > [email protected] > > https://lists.swift.org/mailman/listinfo/swift-evolution > > _______________________________________________ > swift-evolution mailing list > [email protected] > https://lists.swift.org/mailman/listinfo/swift-evolution >
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