[swift-evolution] Pitch: Progress Tracking in Swift

cocoadev at charlessoft.com cocoadev at charlessoft.com
Mon Jan 18 21:39:19 CST 2016

On 2016-01-18 22:24, FĂ©lix Cloutier wrote:
> In terms of which functions need it, I think that reporting progress
> is a relatively niche feature.

How is it niche? Very few apps don't have any places where progress 
tracking (and user cancellation) would be useful, and it's currently 
something that has to be done with workarounds that are either clunky or 

> I would by far prefer that we work on
> infrastructure to implement a library-driven solution. To me, it would
> be a missed opportunity to show off what the language can (will be
> able to) do without having to bake it into the compiler.
> For instance, this could probably be solved without specific compiler
> support if Swift had a macro system and resumable functions.

Apple has repeatedly stated in the past that the lack of macros/a 
preprocessor is supposed to be a feature, not a bug (cf. 
https://developer.apple.com/swift/blog/?id=4). I know there have 
occasionally been some statements on the lists contradicting the 
official stance, but nonetheless I'm not sure we can count on Swift 
gaining a macro system. Also, implementing things like this via macros 
seems a bit... icky to my personal tastes.

Are there any plans to add resumable functions to Swift? I know it's 
been pitched a few times, but it didn't seem to me like it gained much 

> Also, the first two arguments have merit, but it's highly improbable
> that you'll be able to use whatever solution we come up with in OSes
> older than OS X 10.11 or iOS 9 anyway.

All additions to Swift so far have been back-portable to 10.9, given 
that the runtime gets bundled into the app.


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