[swift-evolution] #available has a huge anti-pattern.

[Félix Cloutier]

But isn't it exactly across platforms that feature detection is the most important?

Félix

> Le 3 févr. 2016 à 16:03:28, Douglas Gregor <dgregor at apple.com> a écrit :
> 
> 
>> On Feb 3, 2016, at 1:02 PM, Félix Cloutier <felixcca at yahoo.ca <mailto:felixcca at yahoo.ca>> wrote:
>> 
>> Won't it be a concern with a cross-platform Swift?
> 
> #available is currently only implemented for Apple platforms. If someone wants to extend it to another platform, they need to do so in a manner that gives it consistent semantics.
> 
> 	- Doug
> 
>> 
>> Félix
>> 
>>> Le 3 févr. 2016 à 15:47:15, Douglas Gregor via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> a écrit :
>>> 
>>>> 
>>>> On Feb 3, 2016, at 5:10 AM, Jean-Daniel Dupas via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>> 
>>>> Using function availability has proven fragile in the past too. A function may be present but private on older system, and have a slightly different behavior or crash, and so should not be used.
>>> 
>>> This is a failing of the -respondsToSelector: idiom for checking availability. Swift’s #available feature checks the actual OS version, so it doesn’t suffer from this problem.
>>> 
>>> 	- Doug
>>> 
>>>> 
>>>> 
>>>>> Le 2 févr. 2016 à 11:03, James Campbell via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> a écrit :
>>>>> 
>>>>> Coming from a web background (before my iOS career) to me #avaliable has huge problem. It encourages fragility.
>>>>> 
>>>>> In my eyes we should encourage two types of detection: Features to make code more adaptable to different environments and language version detection: so we can understand the actual code.
>>>>> 
>>>>> See this example below:
>>>>> 
>>>>> func magic(object: Object)
>>>>> {
>>>>>   if(#avaliable(9.0, 10))
>>>>>  {
>>>>>   object.foo()
>>>>>  }
>>>>> }
>>>>> 
>>>>> Ideally for me I would love to check if the foo function exists like so:
>>>>> 
>>>>> func iOS9OnlyProtocolFunction(object: Object)
>>>>> {
>>>>>   if(#avaliable(Object.foo))
>>>>>  {
>>>>>     object.foo()
>>>>>  }
>>>>> else 
>>>>> {
>>>>>   object.baz()
>>>>>  }
>>>>> }
>>>>> 
>>>>> I think this encourages feature detection which results in less fragile code. What I would love to do is also to extend this to extensions so we could encourage polyfills.
>>>>> 
>>>>> extend object where not_avaliable(Object.foo) 
>>>>> {
>>>>>   func foo() 
>>>>>  {
>>>>>    //Polyfill for platforms which don't support the Object.foo method
>>>>>  }
>>>>> }
>>>>> 
>>>>> Not sure about compiler details but being able to polyfill the function results in much cleaner code for me. I love this approach from the web, so I created my own Objective-C Library to do this:
>>>>> 
>>>>> https://github.com/jcampbell05/Polly <https://github.com/jcampbell05/Polly>
>>>>> ___________________________________
>>>>> 
>>>>> James⎥Lead Engineer
>>>>> 
>>>>> james at supmenow.com <mailto:james at supmenow.com>⎥supmenow.com <http://supmenow.com/>
>>>>> Sup
>>>>> 
>>>>> Runway East
>>>>> 
>>>>> 
>>>>> 10 Finsbury Square
>>>>> 
>>>>> London
>>>>> 
>>>>> 
>>>>> EC2A 1AF 
>>>>> 
>>>>> _______________________________________________
>>>>> swift-evolution mailing list
>>>>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>>>>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>>> 
>>>> _______________________________________________
>>>> swift-evolution mailing list
>>>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>>>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>> 
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160203/8baecc17/attachment.html>