Lens are a term from functional programming theory (I think largely Haskell in particular?). I don't know much about it, but here's somewhere to start: https://www21.in.tum.de/teaching/fp/SS15/papers/17.pdf
l8r Sean Sent from my iPad > On 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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