[swift-evolution] When to use argument labels (a new approach)

Dave Abrahams dabrahams at apple.com
Wed Feb 3 16:34:19 CST 2016

on Wed Feb 03 2016, Matt Whiteside <swift-evolution at swift.org> wrote:

> I have one comment (below) about this part:
>> On Feb 2, 2016, at 18:59, Paul Cantrell via swift-evolution
>> <swift-evolution at swift.org> wrote:
>> I have reservations about this. It doesn’t generalize perfectly well:
>> 	a.tracksHavingMediaType("Wax Cylinder”, andPianist: “Brahms”)
>> …strikes me as awkward compared to one of these:
>> 	a.tracksHaving(mediaType: "Wax Cylinder”, pianist: “Brahms”)
>> 	// or 
>> 	a.tracksMatchingCriteria(mediaType: "Wax Cylinder”, pianist: “Brahms”)
>> 	// or even
>> 	a.tracks(mediaType: "Wax Cylinder”, pianist: “Brahms”)
>> …especially since, in a method of that form, _all_ the arguments are
>> likely to have a default value of nil:
>> 	a.tracks(mediaType: "Wax Cylinder”)
>> 	a.tracks(pianist: “Brahms”)
> I prefer the original:
> a.tracksHavingMediaType("Wax Cylinder", andPianist: "Brahms”)
> to any of these,
> a.tracksHaving(mediaType: "Wax Cylinder", pianist: "Brahms")
> // or
> a.tracksMatchingCriteria(mediaType: "Wax Cylinder", pianist: "Brahms")
> // or even
> a.tracks(mediaType: "Wax Cylinder", pianist: "Brahms”)
> Because to me, the 3 alternatives, especially the last one, all read
> more like hashmap accesses than method calls.  In other words, they
> make it appear as if you are passing in arbitrary keys to be queried,
> rather than calling one specific method.

I *think* I understand what you like and why you like it, but I can't
say I understand your rationale.  To test my understanding, what do you
think of this:

      a.tracksHaving(mediaType: "Wax Cylinder", andPianist: "Brahms")




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