[swift-evolution] [Review] SE-0023 API Design Guidelines

Sat Jan 23 14:25:08 CST 2016

True, though that’s partly an issue with Swift’s limitations on how certain types of protocols can be used (and I believe is the subject of another discussion, though the thread escapes me at the moment).

Still, I don’t think that matters when it comes to naming them; I still think that things like CollectionType should just be the Collection protocol, since the fact that it’s a protocol makes it clear that its purpose is to define the requirements of a collection. If a class or struct then comes along that’s also called Collection then that’s an issue for how naming conflicts are resolved (i.e- namespaces) IMO.

> On 23 Jan 2016, at 16:25, Kevin Lundberg via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Many of Java's interfaces also conform to the standard swift uses, with things like runnable/comparable. Those define capabilities and are named with the same reasoning that the api guidelines propose, so it's easy to infer that they are interfaces from the name. I haven't worked in Java in a while so I could be forgetting other interfaces that don't follow this trend though, but interfaces in Java are more easily swapped with classes than protocols are in swift anyways (since protocols with associated types cannot be used as the type of a variable or whatnot).
> 
> --
> Kevin Lundberg
> 
> On Jan 23, 2016, at 10:27 AM, Haravikk <me at haravikk.com <mailto:me at haravikk.com>> wrote:
> 
>> Since I learned object-oriented programming in Java, I never understood the need for suffixes and prefixes at all, as Java’s package system makes for very simple namespaces for everything in the event that simply using a class/interface name is unclear.
>> 
>> I’d say that personally I don’t see why CollectionType shouldn’t just be Collection, in cases where several things are named Collection we should really have some kind of disambiguation mechanism anyway, perhaps with some special cases for specifying when you want a protocol rather than a class/struct.
>> 
>> In my ideal world every language would would follow Java’s example on name-spaces, while avoiding emulating its horrific security record ;)
>> 
>>> On 23 Jan 2016, at 14:52, Thorsten Seitz via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> I never liked the convention of distinguishing between interfaces and classes by prepending an „I“ for interfaces in other languages and I’m not overly fond fond of the suffix „Type“ currently used in Swift protocols.
>>> This is the same as prefixing (or suffixing) variable names with something to express their type, e.g. `String sName` or `int iLength`.
>>> That’s what we have type information for. 
>>> 
>>> And because of the substitution principle it should make no difference whether I have a protocol or a struct or class. What is a `CollectionType` vs. a `Collection`? Is it the type of a `Collection`, i.e. a meta type? Why not simply `Collection` if it describes what a collection is? 
>>> I guess its often more the problem of finding a suitable different name for the implementation and that’s why I sometimes wonder whether it might make sense to give protocols their own namespace…
>>> 
>>> In short, I am not fond of the suffix „Type“ (but I would dislike the suffix „Protocol“ or prefixes like „I“ or „P“ even more).
>>> 
>>> I’m open to debate, though :-)
>>> 
>>> -Thorsten
>>> 
>>> 
>>> 
>>> 
>>> 
>>>> Am 23.01.2016 um 06:25 schrieb Kevin Lundberg via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>>:
>>>> 
>>>> > Protocols that describe what something is should read as nouns (e.g. Collection). Protocols that describe a capability should be named using the suffixes able, ible, or ing (e.g. Equatable, ProgressReporting).
>>>> 
>>>> I personally like the idea behind the current convention for protocols that describe a thing (IntegerType, CollectionType, etc) where there is a suffix of Type appended to the end, so I give this specific part of the proposal a -1. The specific wording of the protocol's name is not so important as the recognition at a glance that this is a protocol vs a concrete type. I like being able to infer at a glance how I'm expected to use a specific type reference based on its name alone; otherwise I may have to refer back to the type definition to refresh my memory of whether or not it is in fact a protocol or is something else.
>>>> 
>>>> This change could also lead to confusion among some developers. For someone who is new to Swift, would they know they should use Bool over Boolean if they've seen both types before? Both names look reasonable to store a boolean value, but the semantics of each type differ significantly. Someone may try to have a type conform to Bool instead of Boolean, which would obviously not work, but could cause some consternation for developers who don't know the difference by heart. Naming the protocol BooleanType at least calls out that this may not be conceptually the same as a plain boolean value, which could make a developer think twice before trying to use that over Bool.
>>>> 
>>>> Removing some common prefix from these kinds of protocols could also run the risk of unintentionally shadowing type names, if someone wanted to write their own Collection or Error struct or class for     instance, or if a pre-existing concrete type in their code turned out to unexpectedly shadow a protocol in a new dependency that they want to add. These situations would not cause any technical hiccups due to module namespacing, but it could lead to confusion when a developer forgets to qualify the name and tries to use one type where the other is expected.
>>>> 
>>>> In short, appending Type (or something like it) i think is a reasonable convention to keep around for non-behavioral protocols.
>>>> 
>>>> As far as alternatives to 'Type', I personally don't like the suffix 'Protocol' as much (which is suggested as a disambiguation option in the related standard library review), since 'Type' is shorter, feels nicer to read, and describes the purpose of the protocol well to me. C#'s approach of prefixing all interfaces with a capital I would be even more succinct, but I personally don't think that approach would     look nice to read either. (PCollection, PBoolean? Ick.) 
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