> On Jun 22, 2016, at 5:51 PM, John McCall <rjmcc...@apple.com> wrote:
>
>
>> On Jun 22, 2016, at 12:15 AM, L. Mihalkovic via swift-evolution
>> <swift-evolution@swift.org> wrote:
>>
>> Func asOpt<T>(v:Any) -> Optional<T> {
>> If let val = v as? T {
>> Return val
>> }
>> Return nil
>> }
>> Regards
>> LM
>> (From mobile)
>
> This is just:
> return v as? T
Had more code where i took it from... I thk it is one of these simple thgs that
u never forget but may not be immediate to thk abt. Maybe worth adding to doc
comment for Optional<> (forgive if is there already)
>
> John.
>
>>
>>> On Jun 22, 2016, at 7:11 AM, Charlie Monroe via swift-evolution
>>> <swift-evolution@swift.org> wrote:
>>>
>>> Unfortunately, this is not as easy, because automatic bridging won't be
>>> applied:
>>>
>>> let myString: String? = "Hello"
>>> let anyValue: Any = myString
>>>
>>> myString as? AnyObject // _NSContiguousString
>>> anyValue as? AnyObject // nil, since String is struct
>>>
>>> let array: [String]? = ["Hello"]
>>> let anyArray: Any = array
>>> anyArray as? AnyObject // nil
>>> anyArray as? [AnyObject] // nil
>>> array as? AnyObject // ["Hello"]
>>>
>>> And this goes for strings, arrays, dictionaries and possibly other types.
>>> Which means that you need to handle manually all of the bridging to ObjC
>>> types, which has really grown in Swift 3, taking into account all the
>>> Foundation types that are now structs.
>>>
>>> Should this then be considered compiler bug that bridging isn't taken into
>>> account?
>>>
>>> Nevertheless, I'd still find it useful exposing the isOptional() function
>>> as well as the asOptional which would allow a cast from Any to
>>> Optional<Any> which is not possible at all at this moment since any such
>>> cast will pick up the Optional first:
>>>
>>> let myString: String? = "Hello"
>>> let anyValue: Any = myString
>>> if let value = anyValue as? Any {
>>> value.dynamicType // This is still Optional<String>, not naively just
>>> the value of the optional
>>> }
>>>
>>>
>>>
>>>> On Jun 21, 2016, at 8:18 PM, Joe Groff <jgr...@apple.com> wrote:
>>>>
>>>> 'as?' should already do this. If you have an Any that contains an
>>>> Optional<T> and cast 'any as? T', you'll get the value inside the Optional
>>>> if there is one, or the cast will fail if the optional is nil or the type
>>>> doesn't match.
>>>>
>>>> -Joe
>>>>
>>>>> On Jun 20, 2016, at 11:00 PM, Charlie Monroe via swift-evolution
>>>>> <swift-evolution@swift.org> wrote:
>>>>>
>>>>> I've recently written a CoreData editor on iOS which automatically
>>>>> generates UI based on the model which is described using classes such as
>>>>> PrimitiveProperty, etc. Since it automatically sets the value on the
>>>>> entity, it needs to convert the value to AnyObject in order to pass it to
>>>>> setValue(_:forKey:), so it needs to be able to detect whether the value
>>>>> is Optional and in case it is, either transform the non-nil value to
>>>>> AnyObject (String -> NSString, Array -> NSArray, ...). Which is currently
>>>>> really hard to achieve:
>>>>>
>>>>> var obj: IndexPath? = IndexPath()
>>>>> let anyValue: Any = obj
>>>>> anyValue.dynamicType /// Optional<Foundation.IndexPath>.Type
>>>>>
>>>>> /// Using only anyValue, determine if it's Optional and retrieve its
>>>>> value if
>>>>> /// non-nil as AnyObject.
>>>>> func isOptional(anyValue: Any) -> Bool {
>>>>> // Error: Cannot downcast from 'Any' (aka 'protocol<>') to a more
>>>>> // optional type 'Optional<_>'
>>>>> return anyValue is Optional
>>>>> return anyValue as? Optional != nil
>>>>> ...
>>>>> }
>>>>>
>>>>> Unless there are major reasons why it's not exposed, I'd propose
>>>>> introducing a new function isOptional(anyValue: Any) -> Bool, which would
>>>>> simply call Builtin.isOptional just like _isOptional does in
>>>>> Builtin.swift. (which pretty much is just taking the current _isOptional,
>>>>> removing underscore and marking it public).
>>>>>
>>>>> However, this still doesn't help with the issue of retrieving the value
>>>>> of the Optional. You now know the value in `anyValue` is Optional, but
>>>>> there is no good way to cast it to e.g. Optional<AnyObject>. Here we're
>>>>> getting into a vicious cycle that Any can be an Optional which is Any.
>>>>>
>>>>> My second part of the proposal introduces another function:
>>>>>
>>>>> func asOptional<T>(anyValue: Any) -> Optional<T>?
>>>>>
>>>>> Which will:
>>>>> - return nil if !isOptional(anyValue)
>>>>> - return a non-nil value only if `anyValue` contains in fact an Optional
>>>>> of type T.
>>>>>
>>>>> Usage:
>>>>>
>>>>> if let anyObjOptional: AnyObject? = asOptional(anyValue: anyValue) {
>>>>> if let anyObj = anyObjOptional {
>>>>> // anyObj is now the actual content of the optional.
>>>>> }
>>>>> }
>>>>>
>>>>> As a sidenote, this is my current workaround:
>>>>>
>>>>> private protocol _XUOptional {
>>>>> var objectValue: AnyObject? { get }
>>>>> }
>>>>>
>>>>> extension Optional: _XUOptional {
>>>>> var objectValue: AnyObject? {
>>>>> switch self {
>>>>> case .None:
>>>>> return nil
>>>>> case .Some(_):
>>>>> return self! as? AnyObject
>>>>> }
>>>>> }
>>>>> }
>>>>>
>>>>> if let optional = anyValue as? _XUOptional {
>>>>> let object = optional.objectValue
>>>>> /// ...
>>>>> }
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>> swift-evolution@swift.org
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>>>
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