1

i have an enum that looks like

enum State 
{
    case alabama 
    case arkansas 
    ...
}
enum Province 
{
    case ontario 
    case quebec 
    ...
}

and a super-enum that looks like

enum Region 
{
    case state(State)
    case province(Province)
}

now i need some protocol to abstract over types that can encode a State, e.g. State itself, and Region.

protocol TypeThatCanEncodeState
{
    static 
    func state(State) -> Self
}

extension Region:TypeThatCanEncodeState {}
extension State:TypeThatCanEncodeState 
{
    static 
    func state(_ state:Self) -> Self 
    {
        state
    }
}

what’s a better name for the “TypeThatCanEncodeState” protocol? ExpressibleByState, LosslessStateConvertible, StateStorage, etc. just don’t feel right.

“StateEncoder” makes more sense semantically, but i don’t want to give the impression that the protocol has anything to do with Encoder or Encodable.

2

Maybe ConstructibleFromState? Though would this be that much more useful than say, abstracting over the constructed type T and then taking a (State) -> T function wherever you’d want to accept this protocol?

The semantics of the protocol seem a bit underspecified to be particularly useful.

2 Likes
3

to oversimplify, what i currently have are APIs that take States as input, and generate aggregates of either States or Regions:

func renderAsStates(states:[State]) -> HTML.Element<State>
func renderAsRegions(states:[State]) -> HTML.Element<Region>

and i would like to unify them as

func render<T>(states:[State], as _:T.Type = T.self) -> HTML.Element<T>

the closure-based approach doesn’t benefit from type inference, and there are a lot of call sites that would all receive the same closure.

overall, you’ve probably got a good point though, ConstructibleFromState probably is not pulling its weight here…

4

Yeah, point taken. This does feel like a bag-of-syntax protocol, but sometimes those can let you do some nice boilerplate reduction. Though without clear semantics, naming is definitely more difficult. :slightly_smiling_face:

5

i’ve come to recognize that 95% of time spent writing HTML rendering code is time spent on boilerplate reduction. but the boilerplate reduction just requires more boilerplate elsewhere… :frowning:

6

How about StateAlike or RegionAlike? :thinking: