> Le 27 juin 2016 à 00:00, Michael Peternell via swift-evolution
> <[email protected]> a écrit :
>
>>
>> Am 26.06.2016 um 23:03 schrieb Jean-Daniel Dupas via swift-evolution
>> <[email protected]>:
>>
>> Optional are definitely the best way to represent null when parsing JSON.
>>
>>> Le 26 juin 2016 à 22:35, Michael Peternell via swift-evolution
>>> <[email protected]> a écrit :
>>>
>>> Just one question: If I have functions
>>>
>>> json_encode(j: JSON) -> String
>>> and
>>> json_decode(j: String) -> JSON throws
>>
>> If the string is valid JSON, it return .some() optional, if ti is empty, it
>> returns .none() optional, and if it is invalid, it throws.
>
> again, `.none()` is not fully specified. So your answer isn't really an
> answer to my question. There is
Optional<Any> (aka Any?) is a fully defined type.
> let null1: String? = nil
> let null2: Int? = nil
> let null3: Any? = nil
>
> and null1, null2 and null3 are three different concrete values. You are
> making it too easy for yourself when you just say `.none()`, without
> specifying the type you are referring to.
>
> Also, `let x = nil` does not even compile, for exactly this reason. So again,
> how do you want to represent a JSON null in Swift?
>
> let json_null: ... = ... // ???
> let myJSONdict = ["a":2, "b":json_null]
As I said, myJSONdict can perfectly be represented as a [String:Any?]
dictionary.
> -Michael
>
>>
>>> what should be the type of JSON? What should '{"a":2,"b":null}' decode to?
>>
>> Dictionary<String, Any?>
>>
>>> What should the type of the JSON null value be in Swift?
>>
>> Optional<Any>.none()
>>
>>> I think String and String? and String??? are wrong in this case.
>>>
>>> I'm not saying that I'm convinced that NSNull() is the best way to
>>> represent null in this case. I just want to explain the use case that I was
>>> thinking of.
>>
>> I hardly can think of a better use case than parsing JSON to demonstrate
>> than Optional are a far better solution to represent a null value than
>> NSNull.
>>
>>> -Michael
>>>
>>>> Am 26.06.2016 um 19:53 schrieb David Rönnqvist via swift-evolution
>>>> <[email protected]>:
>>>>
>>>> I'm not convinced that Swift needs more than on way of representing the
>>>> lack of a value. As far as I've understood (and remember), NSNull main
>>>> reason to exist is that it's an actual object and won't for example
>>>> terminate array literals. From what I've observed of people who are new to
>>>> Objective-C, NSNull is a big surprise, both its general existence but also
>>>> when to expect it (read check for NSNull to make sure one doesn't crash)
>>>> and when not to.
>>>>
>>>> The way I've imagined that the same problem would be solved in Swift is
>>>> with an optional, optional value. That is: if a field in a response can
>>>> either be set or not, that's an optional. If that field can either contain
>>>> a value or the explicit lack of a value that's another optional:
>>>>
>>>> let nickname: String?? = "Little Bobby Tables"
>>>>
>>>> As I see it, this is both safer (requiring that the inner nil value is
>>>> dealt with), serves as a documentation of when an explicit missing value
>>>> is expected and when it's not, and is more consistent.
>>>>
>>>> I would still expect a newcomer to wonder why there is two question marks
>>>> in some places, but I'd imagine that that explanation would feel more
>>>> logical.
>>>>
>>>> And it's (still) possible (at least in the latest Swift Playground) to
>>>> safely unwrap both levels:
>>>>
>>>> if case let name?? = nickname { }
>>>>
>>>> - David
>>>>
>>>> Sent from my iPad
>>>>
>>>> On 24 Jun 2016, at 11:32, Brent Royal-Gordon via swift-evolution
>>>> <[email protected]> wrote:
>>>>
>>>>>> Not really. What is the type of Optional.none? `let empty =
>>>>>> Optional.none` does not compile, it says "Generic parameter 'Wrapped'
>>>>>> could not be inferred". NSNull() is a unique concrete value, and it's
>>>>>> compatible with Objective C, NSObject and AnyObject. We could of course
>>>>>> use `Optional<Int16>.none`, but someone else may use
>>>>>> `Optional<AnyObject>.none` instead. The extra type information is just
>>>>>> misleading in this case.
>>>>>
>>>>> If you want a single, unique value, use `()`.
>>>>>
>>>>> But I'm not sure why you wouldn't just make this member an Optional<Any>
>>>>> in the first place. Is there some reason that wouldn't be suitable?
>>>>>
>>>>> --
>>>>> Brent Royal-Gordon
>>>>> Architechies
>>>>>
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