[swift-evolution] [Review] SE-0006 Apply API Guidelines to the Standard Library

Howard Lovatt howard.lovatt at gmail.com
Thu Jan 28 22:33:04 CST 2016

For protocols named XXXble I think they should have a main method named
XXX. If this were adopted then many protocol names would change, e.g.:

    1. ForwardIndexType would be Advanceable because it has advance methods
and method successor() would be renamed advance().
    2. Indexable would be Subscriptable because it has a subscript method.
    3. Etc.

On 29 January 2016 at 05:03, Erica Sadun via swift-evolution <
swift-evolution at swift.org> wrote:

> On Jan 27, 2016, at 11:42 PM, Dave Abrahams via swift-evolution <
> swift-evolution at swift.org> wrote:
> on Wed Jan 27 2016, Dave <swift-evolution at swift.org> wrote:
> Huh… Yeah, you’re right. I guess I saw “CollectionType” and
> “CustomStringConvertible” or something and made a connection that
> wasn’t there.
> Well, FWIW, that convention (plus the occasional “HasNoun”, and
> -ableType for constraining the element of custom collections) tends to
> work well for me.
> What’s been the deciding factor between -Type and -able so far?
> When there's no reasonable -able or -ible name, use -Type.
> This is where I never know whether to keep my nose out of things or just
> jump in. I find there are generally two kinds of protocols: verby-ones
> ("this is how this thing works") and nouny-ones ("this is what this thing
> is"). Here's the guidance I've been giving:
> *Swift protocols describe the surface that connect a feature provider API
> with its consumer. Protocols establish a communication contract. They
> ensure a fit between each required member and the provider’s
> implementation. It’s like whether a virus can attach to a host cell’s
> receptors, or whatever the actual biological equivalent is. **The
> standard library describes protocols using nouns (typically ending in Type,
> e.g. MirrorPathType, MutableCollectionType, ErrorType) and adjectives
> (typically ending in ble, like Streamable, Strideable,
> ArrayLiteralConvertible). The former more commonly discuss what a
> conforming type is and the latter what it does.  *
> *When naming a protocol, you’re not limited to Type and ble endings. Your
> protocol can be, for example, a DataProvider or a FloatConsumer. A protocol
> can describe a relationship DownloadProcessingDelegate or
> ListViewDataSource. You may implement an OutputDestination or an
> IntegerSink. The current API Design guidelines say "omit needless words",
> so you might prefer to go with DataProvider over DataProviderType or
>  MirrorPath over MirrorPathType, but I wouldn't give much more constraint
> to naming beyond that.*
> For example, for "HasNoun", I'd go with something more like
> NounContainingType or NounSupplier.
> Non-Abrahams Dave writes: "I like -Type for protocols that can only be
> used a generic constraint, and -able/-ible for protocols that can be
> “concrete” types.
> And Canonical Dave replies: "But that's not how they're used.  I'd have to
> rename Equatable and Comparable to follow that convention."
> I agree in that I'm not convinced it's the role of a protocol to describe
> implementation details. (I'd say the same for method names, but that's
> different thread about mutability and side effects, etc). Going that way
> leads you to over-designated hungarian-esque guidelines that I'd rather
> keep loose, friendly, and sensible.
> -- Erica
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  -- Howard.
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