[swift-users] Printing Enums?

Slava Pestov spestov at apple.com
Mon Jul 17 17:40:41 CDT 2017

There’s already a radar filed for this (I don’t know if there’s a JIRA bug though).

The problem is that the standard library’s reflection mechanism only knows how to map the in-memory representation of an enum to a case name for native Swift enums. Objective-C enums are represented by their ‘raw value’, and we don’t store the mapping in a way that’s accessible to the reflection code.


> On Jul 17, 2017, at 3:33 PM, Alex Blewitt via swift-users <swift-users at swift.org> wrote:
>> On 17 Jul 2017, at 15:15, Michael Rogers via swift-users <swift-users at swift.org <mailto:swift-users at swift.org>> wrote:
>> Hi, All:
>> Can someone please enlighten me as to why the first enum works as expected, giving me Melbourne, but the second gives UIModalPresentationStyle rather than fullScreen?
> Sure - it's because it's an alias that is imported via Objective-C rather than defined in Swift:
> typedef NS_ENUM(NSInteger, UIModalPresentationStyle) {
>         UIModalPresentationFullScreen = 0,
>         UIModalPresentationPageSheet NS_ENUM_AVAILABLE_IOS(3_2) __TVOS_PROHIBITED,
>         UIModalPresentationFormSheet NS_ENUM_AVAILABLE_IOS(3_2) __TVOS_PROHIBITED,
>         UIModalPresentationCurrentContext NS_ENUM_AVAILABLE_IOS(3_2),
>         UIModalPresentationCustom NS_ENUM_AVAILABLE_IOS(7_0),
> (you can see this in the UIViewController.h file in the UIKit, which is found underneath your Xcode install)
> The importer notes that the name of such typedef'd constants effectively become translated into an enum as far as Swift source code is concerned, but it's a different kind of case.
> Having said that, it might be a bug in the case that the description of the constant isn't the name of the element type. It would be worth raising this on bugs.swift.org <http://bugs.swift.org/> and use this example in case there's something that can be done to fix it.
> Alex
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> swift-users at swift.org
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