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

[Grant Kemp]

Thanks for the lovely welcome, and for sharing your perspectives.

It sounds like I am not alone on this.
In terms of the timings, given the vast number of:
- 3rd party libraries
- Open source apps
- Enterprise projects
that leverage completion handlers, and are steadfastly stripping their
argument labels away and wondering why this useful feature is gone.  To
protect Swift's great reputation for swiftness, readibliity and clarity, I
would quite like to have those "stripping" out efforts avoided before
everyone has fully jumped to Swift 3.

I would quite like a  fix included in the 3.x branch if its in any way
possible ( to agree with Xiaodi Wu) otherwise I will just have to bite the
bullet and know that there is sunshine on the horizon in the form of Swift
4.

Cheers

On Mon, 17 Oct 2016 at 00:23 Xiaodi Wu <xiaodi.wu at gmail.com> wrote:

> 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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