I cannot remember any use of such a feature but instead of a language feature
there is also a reasonable library solution:
// inspired by the lens idea (of Joe Groff I think)
// there is probably a better name
func lens<T>(value: T, lensClosure: inout T -> ()) -> T {
var value = value
lensClosure(&value)
return value
}
// usage
let john = (firstName:"John", lastName:"Doe")
let alice = lens(john) { $0.firstName = "Alice" }
Kind regards
- Maximilian
> Am 23.03.2016 um 09:06 schrieb Zsolt Szatmári via swift-evolution
> <[email protected]>:
>
> Dear All,
>
> The only thing I am really missing right now from Swift is described as
> following. This works in some other languages, e.g. F#, Kotlin, and Haskell.
>
> F# example (taken from
> https://fsharpforfunandprofit.com/posts/correctness-immutability/)
>
> let john = {firstName="John"; lastName="Doe"}
> let alice = {john with FirstName="Alice"}
>
> Current way to do this in Swift is:
>
> let john = (firstName:"John", lastName:"Doe")
> var alice = john
> alice.firstName = "Alice"
>
> This might seem to be a nuance, but it's more cumbersome (especially if one
> wants to do this frequently), and we are left with a var at the end.
> Also, this idea rhymes with the current direction of removing var arguments
> from functions.
> What do You think? Thank You.
>
> Zsolt
>
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