[swift-evolution] [Proposal Idea] dot shorthand for instance members

Matthew Johnson matthew at anandabits.com
Fri Dec 18 07:05:42 CST 2015

> On Dec 18, 2015, at 6:52 AM, Al Skipp <al_skipp at fastmail.fm> wrote:
>> On 18 Dec 2015, at 03:27, Matthew Johnson via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> Swift currently offers dot shorthand for static members of type Self in type contexts expecting a value of the type in question.  This is most commonly used with enum cases.
>> Swift does not currently offer shorthand for instance members.  Introducing a shorthand for instance members would improve clarity and readability of code in common cases:
>> anArray.map{$0.anInstanceMethod()}
>> becomes:
>> anArray.map(.anInstanceMethod())
>> This shorthand would work in typing contexts expecting a single argument function.  It would allow abbreviated access to any visible instance property getter or instance method on the type of the argument.  Of course the return type would need to match the return type expected by the context or a type mismatch compiler error would occur.
>> The readability advantage is arguably small but it does exist.  The feature also aligns very well with an existing language feature.
>> I think it’s an interesting idea and am wondering whether others feel like it is something worth pursuing or not.
>> Matthew
> I’d be interested to hear peoples thoughts regarding this proposal. I’m personally in favour, but perhaps there are potential issues with the suggestion?
> It’s only a small visual change, but I think it is a syntactic improvement. Let’s pretend for a moment that the current syntax was:
> anArray.map(.anInstanceMethod())
> I’m not sure many people would argue for it to be changed to:
> anArray.map { $0.anInstanceMethod() }

Thanks Al.  I should have also pointed out that the syntactic advantage is a bit greater in other contexts where the braces would not replace parentheses:

struct S {
  var predicate: String -> Bool

var s = S()
s.predicate = { $0.hasPrefix(“abc”) }

s.predicate = .hasPrefix(“abc”)

It’s not a super important change, but maybe a low-hanging fruit item that can improve clarity and readability.

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