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

[Jay Abbott]

Thanks for the explanation Mateusz, I think I understand. So the enum still
only has 3 cases, SMALL, MEDIUM, and LARGE, but an instance also has some
properties?

So some code to use it might be:
var aFormat = Format.LARGE
aFormat.width = 150 // aFormat is still Format.LARGE - this doesn't change

Is that right?

On Mon, 10 Oct 2016 at 09:06 Mateusz Malczak via swift-evolution <
swift-evolution at swift.org> wrote:

> Hi,
> > Perhaps it is a bit ugly, but I don’t know if allowing stored properties
> on
> > enums is the solution: that looks very ugly to me too.
>
> That may look ugly, but can be very useful, if only you think
> rawValue's are useful then you should also agree that stored
> properties would be useful :)
>
> --
> | Mateusz Malczak
>
>
> 2016-10-10 9:26 GMT+02:00 David Hart via swift-evolution
> <swift-evolution at swift.org>:
> > Perhaps it is a bit ugly, but I don’t know if allowing stored properties
> on
> > enums is the solution: that looks very ugly to me too.
> >
> > On 10 Oct 2016, at 02:36, Erica Sadun via swift-evolution
> > <swift-evolution at swift.org> wrote:
> >
> > I would love to be able to have stored properties in addition to the
> varying
> > elements.
> >
> > Now, I end up creating a secondary struct T and doing case a(T,
> whatever),
> > b(T, whatever), c(T, whatever), etc. where the same associated structure
> is
> > every case, *or* I end up putting the enum into a struct which means the
> > guiding semantics are the struct and not the enumeration. Both approaches
> > are ugly.
> >
> > -- E
> >
> > On Oct 9, 2016, at 6:03 PM, Jay Abbott via swift-evolution
> > <swift-evolution at swift.org> wrote:
> >
> > Mateusz,
> >
> > To me, "Enumeration defines a type with well defined set of possible
> values"
> > seems to contradict the idea of having properties that can have different
> > values. What could you do with this special enum - what would the code
> that
> > uses it look like?
> >
> >
> >
> > On Sun, 9 Oct 2016 at 04:56 Robert Widmann via swift-evolution
> > <swift-evolution at swift.org> wrote:
> >>
> >> I’ve started doing this to try and mimic “Smart Constructors” in Haskell
> >> and I think it works quite well.
> >>
> >> struct Format {
> >>   enum FormatBacking {
> >>     case SMALL(Int, Int)
> >>     case MEDIUM(Int, Int)
> >>     case LARGE(Int, Int)
> >>   }
> >
> >
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> >
> >
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