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

[Joe Groff]

> On Jan 23, 2016, at 11:01 AM, David Owens II <david at owensd.io> wrote:
> 
> What about enums with associated data? Those really are like types. So do we capitalize those?
> 
> Unless those get redesigned, there is really this contrary feel to those and other enum cases. 

Before open sourcing, I had written up some thoughts on this:

https://github.com/apple/swift/blob/master/docs/proposals/EnumStyle.rst

From an API perspective, an enum 'case' behaves similarly to a factory method or initializer on a struct or class, and in native Swift we generally prefer `init`s to static factory methods when possible. We also see a lot of API design in the wild where framework authors paper over the enum-ness of their API enums with initializers:

enum Result<T> {
  case Success(T)
  case Error(ErrorType)

  init(success: T) { self = .Success(success) }
  init(error: ErrorType) { self = .Error(error) }
}

We hadn't settled on our argument label model when we originally designed and implemented enums; I feel like if we had, it's likely we would have favored cases that natively look and feel more like initializers, using labels to distinguish cases:

enum Result<T> {
  case (success: T)
  case (error: ErrorType)
}

-Joe
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160123/a158369a/attachment.html>