[swift-evolution] [Pitch] Improve `init(repeating:count)`

[Rintaro Ishizaki]

I don't think it's worthwhile adding new API.
I think this is simple enough:

let views = Array(AnyIterator(UIView.init).prefix(3))

2017-08-17 21:04 GMT+09:00 Robert Bennett via swift-evolution <
swift-evolution at swift.org>:

> Alternatively, instead of replacing the current definition with an
> autoclosure version, we could leave the current version in place and add a
> version taking a function. This could be especially useful when you’ve
> defined a function like `makeMySpecialKindOfButton() -> UIButton` that does
> a lot of customization to an object before returning it.
>
> Array(repeating: { return UIView() }, count: 3)
> and
> Array(repeating: makeMySpecialKindOfButton, count: 3)
>
> On Aug 17, 2017, at 7:54 AM, Haravikk via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>
> On 17 Aug 2017, at 10:38, Adrian Zubarev via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> This is a small pitch which I will abandon if there is not much appetite
> for such improvement. ;)
>
> I would like to propose an improvement to an initializer of all collection
> types that provide: init(repeating repeatedValue: Element, count: Int).
>
> This change is meant to support reference type initialization on each
> iteration of the internal for-loop rather than copying the same references
> n times.
>
> The change would be really straightforward and should not break existing
> code, except that the behavior would change for class types.
>
> Instead of:
>
> init(repeating repeatedValue: Element, count: Int)
>
> let threeViews = Array(repeating: UIView(), count: 3) // contains 1 view 3 times
>
> we would have:
>
> init(repeating repeatedValue: @autoclosure () -> Element, count: Int)
>
> This simple change would allow us to construct an array of different
> objects instead of an array with n references to the same object.
>
> let threeViews = Array(repeating: UIView(), count: 3) // contains 3 different view
>
> I don't think that changing the existing initialiser is the way to do
> this, as it's not really clear here that the UIView() will be instantiated
> multiple times rather than the same reference copied multiple times. The
> copying behaviour is in fact desirable as it will be significantly faster,
> especially with very large arrays.
>
> I think the better way to achieve this might be add some closure-based
> sequence that returns a closure's result N times, so we could do something
> like this:
>
> let threeViews = Array(Repeat(count: 3) { return UIView() })
>
> i.e- we would initialise Array from a sequence returning a new UIView
> three times. While we could also do an array initialiser with closure,
> using a separate type is probably the cleaner way to do this.
>
> There is already a Repeater type, but this just does the same as the array
> initialiser already does, could be another type I've missed that might do
> what is needed, otherwise it seems to require types like AnyIterator with
> some counting code.
>
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