[swift-evolution] Idea: Named extensions
Brandon Knope
bknope at me.com
Mon May 16 15:27:26 CDT 2016
Here is an attempt to express myself better :)
Objective-C to Swift category to extension conversion loss of descriptive name
Objective-C category:
@interface NSAttributedString (NSAttributedStringDocumentFormats)
// Methods initializing the receiver contents with an external document data. options specify document attributes for interpreting the document contents. NSDocumentTypeDocumentAttribute, NSCharacterEncodingDocumentAttribute, and NSDefaultAttributesDocumentAttribute are supported options key. When they are not specified, these methods will examine the data and do their best to detect the appropriate attributes. If dict is non-NULL, it will return a dictionary with various document-wide attributes accessible via NS...DocumentAttribute keys.
- (nullable instancetype)initWithURL:(NSURL *)url options:(NSDictionary<NSString *, id> *)options documentAttributes:(NSDictionary<NSString *, id> * __nullable * __nullable)dict error:(NSError **)error NS_AVAILABLE(10_11, 9_0);
...
@end
Translated Swift extension:
extension NSAttributedString {
// Methods initializing the receiver contents with an external document data. options specify document attributes for interpreting the document contents. NSDocumentTypeDocumentAttribute, NSCharacterEncodingDocumentAttribute, and NSDefaultAttributesDocumentAttribute are supported options key. When they are not specified, these methods will examine the data and do their best to detect the appropriate attributes. If dict is non-NULL, it will return a dictionary with various document-wide attributes accessible via NS...DocumentAttribute keys.
@available(iOS 9.0, *)
public init(URL url: NSURL, options: [String : AnyObject], documentAttributes dict: AutoreleasingUnsafeMutablePointer<NSDictionary?>) throws
...
}
The self-documenting name of the category is lost when imported in Swift. Some categories have no outward comment describing it because they seem to rely on the category name. For example, this one *does* have a comment describing it that is imported into swift:
Objective-C
/************************ Attribute fixing ************************/
@interface NSMutableAttributedString (NSAttributedStringAttributeFixing)
@end
Swift:
/************************ Attribute fixing ************************/
extension NSMutableAttributedString {
}
Again, the comment is not enforced by the compiler and is a style choice. Names on categories are enforced (except for a class’s private () category)
One moonshot: Are extension’s an implementation detail?
Here is the generated interface for a simple View Controller
internal class ViewController : UIViewController {
override internal func viewDidLoad()
override internal func didReceiveMemoryWarning()
}
extension ViewController {
internal func test()
}
Theoretically, if we had named extensions:
extension ViewController named Test {
internal func test() {
}
}
could be translated to:
internal class ViewController : UIViewController {
override internal func viewDidLoad()
override internal func didReceiveMemoryWarning()
Test:
internal func test()
}
I am not sure if this behavior would be truly desired, but it would allow the methods to remained group under a comment or a header of some sort.
//Phew
Brandon
> On May 16, 2016, at 4:25 PM, T.J. Usiyan <griotspeak at gmail.com> wrote:
>
> I have wanted this feature and floated it a while back. I hope we can get some traction this time but I doubt it will happen soon since additive features are tabled for a time.
>
> On Mon, May 16, 2016 at 3:47 PM, Brandon Knope via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> I think requiring them to be in comments is what’s going to prevent their adoption.
>
> My fundamental stance is that these awesome features that are required in comments will be overlooked by people because:
> • You have to remember the specific syntax
> • There is no code completion which means you have to know the *exact* syntax and spelling
>
> At the end of the day, Swift is a new language, and because of this, is there a new and better way to convey information than just sticking everything in a comment?
>
> With autocomplete we could get something like this:
>
> extension Type, named Name {
> }
>
> This would make it much easier for people to adopt than requiring them to remember a comment syntax.
>
> However, if there is no interest, I will not proceed with a proposal.
>
> Just my .02
> Brandon
>
> Where autocomplete would let you tab between naming the Type and Name
>
>> On May 16, 2016, at 3:24 PM, Erica Sadun <erica at ericasadun.com <mailto:erica at ericasadun.com>> wrote:
>>
>> Most of the Swift docs markup tech is both very new and still evolving. I'm trying to evangelize the technology, and there are now five markup items that actually tie into the code completion engine:
>>
>> Three new doc comment fields, namely - keyword:, - recommended: and - recommendedover:, allow Swift users to cooperate with code completion engine to deliver more effective code completion results. The - keyword: field specifies concepts that are not fully manifested in declaration names. - recommended: indicates other declarations are preferred to the one decorated; to the contrary, - recommendedover: indicates the decorated declaration is preferred to those declarations whose names are specified.
>>
>> -- E
>>
>>
>>> On May 16, 2016, at 1:14 PM, Brandon Knope <bknope at me.com <mailto:bknope at me.com>> wrote:
>>>
>>> I have never seen anyone use this. Why? Because it is relatively unknown and not very “pretty” in my opinion. In the ideal world, everyone would have perfectly formatted and up to date comment, but I am not convinced this is usually the case.
>>>
>>> It’s good for IDE documenting, but:
>>> • Online tutorials do NOT use this in code samples, keeping it from being widely known (and because it looks ugly next to their sample and makes it look more verbose)
>>> • It really does not look nice with the language. It seems like IDE magic
>>> • What about people writing in a text editor or not in Xcode? If they do not get a benefit out of // MARK: or /// - Keyword: why would they use it?
>>>
>>> And a quick read of Matthew’s proposal tells me that it may be beneficial to be able to refer to the name of an extension in the future. I am still reading through his proposal but that’s what I took from it with a quick look.
>>>
>>>
>>> Brandon
>>>
>>>> On May 16, 2016, at 3:08 PM, Erica Sadun <erica at ericasadun.com <mailto:erica at ericasadun.com>> wrote:
>>>>
>>>> Or better yet, the 'Keyword" token offers searchable content that can relate one extension to the other.
>>>>
>>>> /// - Keyword: Lifecycle extension
>>>>
>>>> -- Erica
>>>>
>>>>
>>>>> On May 16, 2016, at 11:33 AM, Michael Peternell via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>>>
>>>>> Why not just use a (documentation) comment?
>>>>>
>>>>> /// The Lifecycle extension:
>>>>> extension ViewController {
>>>>> ...
>>>>>
>>>>> -Michael
>>>>>
>>>>>> Am 16.05.2016 um 18:26 schrieb Brandon Knope via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>>:
>>>>>>
>>>>>> I like to separate methods into their own logical extensions so similar methods are grouped together. I do this mostly with Cocoa Touch where I like all view life cycle methods to be in the same extension:
>>>>>>
>>>>>> extension ViewController {
>>>>>> override func viewDidLoad() {
>>>>>> }
>>>>>>
>>>>>> override func viewWillAppear(animated: Bool) {
>>>>>> }
>>>>>>
>>>>>> override func viewDidDisappear(animated: Bool) {
>>>>>> }
>>>>>> }
>>>>>>
>>>>>> You can document this somewhat by adding a MARK comment:
>>>>>>
>>>>>> // MARK: Lifecylce
>>>>>> extension ViewController {
>>>>>> override func viewDidLoad() {
>>>>>> }
>>>>>>
>>>>>> override func viewWillAppear(animated: Bool) {
>>>>>> }
>>>>>>
>>>>>> override func viewDidDisappear(animated: Bool) {
>>>>>> }
>>>>>> }
>>>>>>
>>>>>> What if we made this more self-documenting by elevating this to a language feature?
>>>>>>
>>>>>> extension ViewController named Lifecycle {
>>>>>> override func viewDidLoad() {
>>>>>> }
>>>>>>
>>>>>> override func viewWillAppear(animated: Bool) {
>>>>>> }
>>>>>>
>>>>>> override func viewDidDisappear(animated: Bool) {
>>>>>> }
>>>>>> }
>>>>>>
>>>>>> Other ways:
>>>>>> extension named Lifecycle ViewController { }
>>>>>> extension named “View Lifecycle" ViewController { }
>>>>>> extension ViewController named “Multi word description” { }
>>>>>>
>>>>>>
>>>>>> For now, this is purely a documenting feature (i.e. Can’t refer to the extension name dynamically or statically in actual code). I think it plays much more naturally with Swift than requiring this to be in the comments and would work across all IDEs and make it easier for people to find a specific extension as well as making their code more self documenting.
>>>>>>
>>>>>> Any thoughts?
>>>>>>
>>>>>> Thanks,
>>>>>> Brandon
>>>>>>
>>>>>>
>>>>>>
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>>>>>
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