[swift-users] for with optional collection?

[Rick Mann]

I love the idea of for in? (Or even for? In). You should pitch that to evolution. 

Sent from my iPhone

> On Feb 10, 2017, at 07:04, Tino Heth <2th at gmx.de> wrote:
> 
> 
>> Is there any concise way to write the following?
>> 
>> if let collection = someOptionalCollection
>> {
>>    for item in collection
>>    {
>>    }
>> }
> I've been thinking about that lately, but haven't had the time to look wether someone on evolution already proposed a "for in?"-loop…
> 
> Imho the "forEach" solution is flawed, because you can't break the loop, and the "?? []" isn't perfect either:
> I hope the compiler can optimise so that the assembly is as fast as the "if let" solution, but even if this is the case, it is not obvious for a human reader.
> 
> This
> 
> extension Optional where Wrapped: Sequence {
> 	var elements: [Wrapped.Iterator.Element] {
> 		switch (self) {
> 		case .none:
> 		return []
> 		case .some(let o):
> 		return Array(o)
> 		}
> 	}
> }
> 
> let test: [Int]? = nil
> for i in test.elements {
> 	print(i)
> }
> 
> looks nice to me (except the return type — I guess there are better options), but I don't expect that the compiler can do much to optimise it.
> 
> for i in? test {
> 	print(i)
> }
> 
> Imho looks even better, but this would need an extension of the language itself…
> 
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