[swift-evolution] [SE-0088] Dispatch API names

[Matt Wright]

> On Jun 20, 2016, at 7:12 PM, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> 
> On Mon, Jun 20, 2016 at 9:05 PM, Brent Royal-Gordon via swift-evolution <swift-evolution at swift.org> wrote:
> > DispatchQueue.async(execute:) and DispatchQueue.sync(execute:)
> > --------------------------------------------------------------
> > The lack of verb in the base name bothers me. The API Design Guidelines say “methods with side-effects should read as imperative verb phrases”. You could argue that the argument label “execute” serves as the verb. However, .async and .sync are most commonly used with trailing closures where the argument label is not present.
> >
> > This issue was brought up during the review, but I did not see it being addressed. Why not name the methods something like .executeAsync(_:) and .executeSync(_:)?
> 
> That feels a little redundant to me. It's worth remembering that the API Guidelines are a means of creating clear APIs, not an end in themselves. It's okay to deviate a little if you get a better result.
> 
> The guideline that methods should "read as imperative verb phrases" applies to the full name, labels and arguments and all, and not just the base name. You'll recall that the original proposal had .asynchronously(execute:), which is very much an imperative phrase. `.async(execute:)` was substituted by popular demand, with "async" being regarded as a term-of-art exception.

Right, the naming here strayed from the guidelines here under the term-of-art exception. None of the various alternatives really fit amazingly well, the async{,hronous} part of the API name communicates an important facet of what the call does. In that it goes away and executes the closure “somewhere else”. I feel this particular point is lost in example such as perform{andWait}. `.asynchronously` was an attempt to move towards the guidelines but it still missed that mark. I believe it’s still clearer to have `.async` as an exception.

> 
> However, I could see us borrowing (and slightly modifying) terminology from Core Data:
> 
>         queue.perform { … }
>         queue.performAndWait { … }
> 
> Compared to the status quo, this is clearer, a better fit for the guidelines, and better at penalizing the disfavored API.
> 
> > DispatchQueue.after(when:execute:)
> > ----------------------------------
> > This one simply doesn’t read grammatically. For example, `queue.after(when: .now) { … }` becomes “queue, after when now …”. Since dispatch_after is semantically just an extended version of dispatch_async (I think), we can name this .executeAsync(after:_:).
> 
> Yeah, I gave a talk about the renaming on Saturday and somebody noted that `when` reads poorly here. Fortunately, `queue.perform(after: .now() + 0.5)` reads pretty well too. :^)
> 
> Or just `queue.after(_:execute:)`, i.e. "after [this time], execute [that routine].”

.after is already going to need some tweaking as I don’t believe the current incarnation is sufficiently named to avoid being ambiguous in the common case. Though, removing the label will also not help in that regard. I agree, there is probably merit in the idea of moving after to being an optional argument on `.async`.

> 
> --
> Brent Royal-Gordon
> Architechies
> 
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