[swift-evolution] [Pitch] Adding in Optional Argument labels for completion handlers

[Xiaodi Wu]

Honestly, given that the detailed implementation is core team-approved, I
wonder if it ought to be just one of those rare pre-accepted proposals
instead. It may not be ABI impacting, but as a bugfix for a Swift 3
proposal there's a good argument it should go out in 3.x. My two cents
anyway.


On Mon, Oct 17, 2016 at 07:16 Austin Zheng <austinzheng at gmail.com> wrote:

> It seems like that link should be added to the 'frequently proposed
> changes' page on the repo. I'll prepare a PR.
>
> Austin
>
>
> On Oct 16, 2016, at 4:09 PM, Xiaodi Wu via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Welcome to the list! It seems the community and core team are in agreement
> about your point. As mentioned previously, the core team has laid out a
> two-step roadmap to restoring argument labels:
>
>
> https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160711/024331.html
>
> Hope that helps!
> On Mon, Oct 17, 2016 at 06:35 Grant Kemp via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Hi all
> A South African in London here and I have decided to make the jump to
> trying to help Swift develop.
>
> I was an android and web developer and swift converted me to iOS
> programming which has become something that I love. I have built several
> apps on iOS and on macOS using it and thoroughly enjoyed it.
>
> One think has made me fall a little out of love with swift 3 was
> the removal of completion handler argument labels which has created:
> 1. Less maintainable code for teams
> 2. Less readable and thus more error prone code
> 3. Slower code to write as now I have to regularly scroll to the top of
> the method to find out what the parameters should be .
> 4. Seems to be at odds with other parts of the api which favours labels.
>
> I have found quite a lot of support from others via my stack overflow
> question here:
>
> http://stackoverflow.com/questions/39613272/xcode-8-function-types-cannot-have-argument-label-breaking-my-build
>
> Here is my suggestion:
> Currently the Swift 3 version does not allow arguments in the
> completionhandler method, which is confusing and not very readable.
>
>     func myMethod(_ completionhandler:(_ downloadedValue:String,_
> isActive:Bool, _ error:NSError)-> Void) {
>         //<<After doing some async method such as downloading from an API
> >>
>
>         completionhandler(myString, true, myError)
>
>     }
>     // INSTEAD: ideally the argument labels should be added optionally to
> be called in the completion method such as below and using a Tuple-like
> syntax to indicate that the method should have the labels
>
>     func myMethod(_ completionhandler:( downloadedValue:String, isActive:
> Bool,  error:NSError)-> Void) {
>
>         //<<After doing some async method such as downloading from an API
> >>
>
>         completionhandler(dowloadedValue:myString, isActive:true,
> error:myError)
>
>     }
>
>
> Thanks for the help ( and any feedback on my idea above )
>
> Thanks for the epic work you are doing !
> --
> Sent from my mobile
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