[swift-evolution] [Guidelines, First Argument Labels]: Prepositions inside the parens
dabrahams at apple.com
Wed Feb 10 17:17:44 CST 2016
on Wed Feb 10 2016, Matthew Judge <matthew.judge-AT-gmail.com> wrote:
> On Tue, Feb 9, 2016 at 2:18 PM, Dave Abrahams via swift-evolution <
> swift-evolution at swift.org> wrote:
>> Hi everybody,
>> Having looked at some examples, the API guidelines working group members
>> that were present this morning agreed we really want prepositions inside
>> the parentheses of method calls.
>> Here are some results for the importer; we're still tuning some of the
>> heuristics but overall we feel very good about the preposition
>> Note that this is not final wording, but here are the guidelines we're
>> working with for first argument labels:
>> A. Try to form a grammatical phrase including the first argument and
>> describing the primary semantics at the call site.
> I assume that A is intended to cover:
> a.addObserver(b) // yes
> a.add(observer: b) // no
I don't know what you mean by "cover." It isn't intended to assign the
"yes/no" decision to those; they both form (the same) grammatical phrase
at the call site. The choice between those two is governed by B, below.
> I believe I can read this behavior into A by inferring "a grammatical
> phrase including [the base name and] the first argument" but I want to make
> sure this is the intent.
>> B. The first argument gets a label when and only when:
>> 1. It does not form part of a grammatical phrase describing the
>> primary semantics. For example,
>> x.dismiss(animated: y)
>> [more examples needed]
>> Note that parameters with defaults never describe the primary
>> semantics. so are always labeled.
>> func invert(options options: SomeOptionSet = ) // yes
>> func invert(_ options: SomeOptionSet = ) // no
>> 2. The method is a factory method; such calls should mirror
>> initializers, with no preposition. For example,
>> let x = UIColor(red: r, green: g, blue: b)
>> let y = monitor.makeColor(red: r, green: g, blue: b)
> If rule B.2 didn't exist
> let y = monitor.makeColor(red: r, green: g, blue: b)
> would still have the first argument labeled by B.1 wouldn't it?
Yes, but you could have done this grammatically, as
let y = monitor.makeColorHavingRed(r, green: g, blue: b)
That's what B2 is designed to prevent.
> (Though without this rule, the guidelines wouldn't be clear on whether
> or not to include prepositions in the argument labels.)
>> 3. It is part of a prepositional phrase
>> a. The label normally starts with the preposition.
>> For example,
>> x.move(from: a, to: b)
>> x.loadValues(forKeys: ["fox", "box", "lox"])
>> b. ...unless the preposition would break a very tight association
>> between parameters:
>> x.moveTo(x: a, y: b)
>> [encourage grouping parameters into higher-level concepts,
>> e.g. Point, in these cases]
> This seems clear and straightforward to apply. The only place where
> this isn't totally clear is when there are multiple prepositions (as
> highlighted in Jacob's response),
Multiple prepositions before the first argument?
> but I think B.3 provides the right level of guidance... much more
> detail will start being too many guidelines and special cases.
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