On more thing:
The result type of my `random()` extension is optional. This might not be
ideal. It is not an expected and likely case that `random()` returns nil. I
would personally prefer it to be non-optional and crash if the array is empty,
just like it would if you tried to reference a non-existing index in the
collection. So, the version I actually prefer is:
extension RandomAccessCollection {
func random() -> Iterator.Element {
precondition(count > 0, "There is no element to random pick.")
let offset = arc4random_uniform(numericCast(count))
let i = index(startIndex, offsetBy: numericCast(offset))
return self[i]
}
}
> On Oct 13, 2016, at 4:08 AM, Jean-Denis Muys <jdm...@gmail.com> wrote:
>
> Thank you for this Hooman, I think this is what I was looking for.
>
> JD
>
> On Thu, Oct 13, 2016 at 4:26 AM, Hooman Mehr <hoo...@mac.com
> <mailto:hoo...@mac.com>> wrote:
>
>> On Oct 12, 2016, at 3:21 AM, Jean-Denis Muys via swift-users
>> <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
>>
>>
>> But this is not very DRY.
>>
>> What would be a more idiomatic way?
>>
>
> The more idiomatic way is to look at API design in a new way. Note these
> points:
>
> 1. `Countable` variant is preferred when you want to deal with integer ranges
> as it more closely matches the element type.
> 2. Both countable range variants share a common protocol conformance already:
> `RandomAccessCollection`
> 3. Swift API design prefers member functions to free functions.
>
> Hence a more idiomatic (Swifty) API would probably be something like this:
>
> extension RandomAccessCollection {
>
> func random() -> Iterator.Element? {
>
> guard count > 0 else { return nil }
>
> let offset = arc4random_uniform(numericCast(count))
>
> let i = index(startIndex, offsetBy: numericCast(offset))
>
> return self[i]
> }
> }
>
> Using the above, both cases work and there is no repetition:
>
> (4..<10).random()
> (4...9).random()
>
> It also makes a lot more possible:
>
> let people = ["David", "Chris", "Joe", "Jordan", "Tony"]
> let winner = people.random()
>
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