Slight amendment for `let` case, which does evidently still require the
explicit `.some`
switch str {
case "foo": print("foo")
case .some(let string): print(string) // `case let .some(string)` also works
case nil: print("nil")
}
> On Jun 28, 2016, at 11:10 AM, Kevin Nattinger via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> I’ve always thought it’s a bit odd, but that’s the way it is. FWIW, if you
> define `T? ~= T?` (switch uses `~=` under the hood), you can use that syntax:
>
> public func ~=<T : Equatable>(a: T?, b: T?) -> Bool {
> return a == b
> }
>
> switch str {
> case "foo": print("foo")
> case "bar": print("bar")
> case nil: print("nil")
> default: print("other")
> }
>
> For better or worse, this prevents you from using the `.some(x)` / `.none`
> version.
>
> You could propose adding this to the standard library to the swift-evolution
> list, see how they react.
>
>> On Jun 28, 2016, at 9:52 AM, Lucas Jordan <lucasjor...@gmail.com> wrote:
>>
>> This is sort of weird right? because comparing nil to a non nil string is a
>> reasonable thing to do:
>>
>> var nilString:String? = nil
>>
>> if nilString == "this always fails" {}
>>
>> is totally reasonable.
>>
>> On Tue, Jun 28, 2016 at 12:33 PM, Kevin Nattinger <sw...@nattinger.net>
>> wrote:
>> No
>>
>> 7> switch str {
>> 8. case "foo": print("case foo")
>> 9. case .none: print("(nil)")
>> 10. }
>> error: repl.swift:8:6: error: value of optional type 'String?' not
>> unwrapped; did you mean to use '!' or '?'?
>> case "foo": print("case foo")
>> ^
>> !
>> Odd error, but at least it suggests it’s an issue with optionaity.
>>
>>
>>> On Jun 28, 2016, at 9:27 AM, Nevin Brackett-Rozinsky
>>> <nevin.brackettrozin...@gmail.com> wrote:
>>>
>>> Does `case "text"?` work?
>>>
>>>
>>> On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution
>>> <swift-evolution@swift.org> wrote:
>>> Case .none:
>>> Case .some("string"):
>>>
>>>
>>> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution
>>> <swift-evolution@swift.org> wrote:
>>>
>>>> Forgive me if this was/is discussed already, I am new to the process
>>>> here....
>>>>
>>>> (code is attached as a playground too)
>>>>
>>>>
>>>>
>>>> Sometimes when I am working with a String? nil can be a reasonable value,
>>>> and what I want to do is something like the following:
>>>>
>>>> import UIKit
>>>>
>>>>
>>>>
>>>> var str:String? = "Hello, playground"
>>>>
>>>>
>>>>
>>>> switch str{
>>>>
>>>> case nil:
>>>>
>>>> print("Nil!")
>>>>
>>>> case "Hello, playground": //it would be super nice if this worked.
>>>>
>>>> print("Match")
>>>>
>>>> default:
>>>>
>>>> print("Some other non nil value?")
>>>>
>>>> }
>>>>
>>>>
>>>>
>>>> But it does not work, the orange text is a compile time error,
>>>> "Expression pattern of type 'String' cannot match value of type 'String?'.
>>>> I realize that this can be replaced with a let statement (case let s where
>>>> s == "Hello, playground":), but that is verbose.
>>>>
>>>> Seems like the compiler could be OK with the orange text, since it is
>>>> clearly not nil.
>>>>
>>>> Thoughts?
>>>>
>>>> -Lucas
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> <NilInSwitchStatements.playground.zip>
>>>> _______________________________________________
>>>> swift-evolution mailing list
>>>> swift-evolution@swift.org
>>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>
>>
>
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