[swift-users] Compact iteration of optional collection?

[Zhao Xin]

You can try container?.forEach(), like

let bb:[String:Int]? = ["aa":1, "bb":2, "cc":3]

bb?.forEach { print($0) }

/*

("aa", 1)

("bb", 2)

("cc", 3)

*/


Zhaoxin

On Fri, Jul 29, 2016 at 6:14 AM, Saagar Jha via swift-users <
swift-users at swift.org> wrote:

> The nil check and creating an empty array have very similar performance,
> in my naïve testing.
>
> Saagar Jha
>
>
>
> On Jul 28, 2016, at 14:59, Jacob Bandes-Storch via swift-users <
> swift-users at swift.org> wrote:
>
> You should test it out — I'd guess there's a good chance it gets optimized
> out.
> On Thu, Jul 28, 2016 at 2:58 PM Rick Mann <rmann at latencyzero.com> wrote:
>
>> Yeah, I suppose that works. Feels a bit clunky, like the language lacks
>> specific support for this (in that it provides specific support for so many
>> other common constructs). But I guess I can make do with that.
>>
>> I suppose there's a bit of a performance hit, in that constructing an
>> empty array and iterating over it is more expensive than a simple nil
>> check, but that's unlikely to cause issues in practice.
>>
>> Thanks.
>>
>> > On Jul 28, 2016, at 14:56 , Jacob Bandes-Storch <jtbandes at gmail.com>
>> wrote:
>> >
>> > How about "for item in someOptionalContainer ?? []"  ?
>> >
>> > On Thu, Jul 28, 2016 at 2:55 PM, Rick Mann via swift-users <
>> swift-users at swift.org> wrote:
>> > I often call methods that return an optional collection. I then iterate
>> over it. The problem is, it's a bit cumbersome to write:
>> >
>> >      if let container = someOptionalContainer
>> >     {
>> >         for item in container
>> >         {
>> >         }
>> >     }
>> >
>> > I wish I could just write
>> >
>> >     for item in someOptionalContainer
>> >     {
>> >     }
>> >
>> > such that if the optional is nil, it just skips the iteration
>> altogether.
>> >
>> > Is there a syntax for that (especially in Swift 3)?
>> >
>> >
>> > --
>> > Rick Mann
>> > rmann at latencyzero.com
>> >
>> >
>> > _______________________________________________
>> > swift-users mailing list
>> > swift-users at swift.org
>> > https://lists.swift.org/mailman/listinfo/swift-users
>> >
>>
>>
>> --
>> Rick Mann
>> rmann at latencyzero.com
>>
>>
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