[swift-evolution] [Proposal] Enums with stored properties

[Xiaodi Wu]

On Wed, Oct 12, 2016 at 2:27 PM, Sean Heber <sean at fifthace.com> wrote:

>
> > With the improved syntax, this could look something like this instead:
> >
> > enum FileError: Error, LocalizedError {
> >     var url: URL { get }
> >
> >     case notFound(url: URL) {
> >         errorDescription = "Could not access the file
> \(url.lastPathComponent) because it could not be found."
> >         failureReason = "The file \(url.lastPathComponent) could not be
> found."
> >         recoverySuggestion = "Please locate the correct file and try
> again."
> >         helpAnchor = "notFound"
> >         url = url
> >     }
> >
> >     case accessDenied(url: URL) {
> >         errorDescription = "Could not access the file
> \(url.lastPathComponent) because access was denied."
> >         failureReason = "We do not have permission to view the file
> \(url.lastPathComponent)"
> >         recoverySuggestion = "You can change the file's permissions
> using the Finder's Get Info window."
> >         helpAnchor = "accessDenied"
> >         url = url
> >     }
> >
> >     case incorrectFormat(url: URL) {
> >         errorDescription = "Could not access the file
> \(url.lastPathComponent) because it was not in the expected format."
> >         failureReason = "The file \(url.lastPathComponent) was not in
> the expected format."
> >         recoverySuggestion = "The file may have become corrupt."
> >         helpAnchor = "incorrectFormat"
> >         url = url
> >     }
> >
> >     case ioError(url: URL) {
> >         errorDescription = "Could not access the file
> \(url.lastPathComponent) because an I/O error occurred."
> >         failureReason = "An I/O error occurred while accessing the file
> \(url.lastPathComponent)."
> >         recoverySuggestion = "Dear Lord, the hard drive may be failing."
> >         helpAnchor = "ioError"
> >         url = url
> >     }
> >
> >     // ... etc ...
> > }
> >
> > I don’t think it can be denied that the second is orders of magnitude
> easier to read and comprehend.
> >
> > Charles
>
> I’m 100% in favor of something approaching this syntax where the
> case-specific values are all grouped by the case and not the other way
> around.
>

This particular suggestion has been made multiple times in the past. It is
a proposal for sugar that did not converge on a consensus during either
Swift 2 or 3 evolution. Since sugar is not in scope now and is still low
priority for phase 2, let's focus on the potentially ABI-impacting issues
here.

l8r
> Sean
>
>
>
>
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