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

Brent Royal-Gordon brent at architechies.com
Mon Jun 20 21:05:46 CDT 2016

> 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.

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. :^)

Brent Royal-Gordon

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