[swift-users] Multiple value-binding patterns in a single switch case

[Jens Persson]

I'm not sure what you are trying to achieve.
Why can't you just do:
label.text = animal.nam
?
Is it because not all Animals have names?
If so, you could perhaps use something like this:

class Animal {}
protocol Named {
    var name: String { get }
}
class Dog: Animal, Named {
    let name = "Dog"
}
class Cat: Animal, Named {
    var name: String {
        return "Cat"
    }
}

let animals: [Animal] = [Cat(), Dog()]

for animal in animals {
    if let namedAnimal = animal as? Named {
        print(namedAnimal.name)
    }
}




On Fri, Jun 9, 2017 at 12:34 PM, Glen Huang via swift-users <
swift-users at swift.org> wrote:

> Hi, I wonder what's the correct way to express something like this in
> swift:
>
> Say I have a superclass with two subclasses:
>
> class Animal {}
> class Dog: Animal {
>     let name = "Dog"
> }
> class Cat: Animal {
>     var name: String {
>         return "Cat"
>     }
> }
>
> And I want to display the name with a switch:
>
> switch animal {
> case let a as Dog, let a as Cat:
>     label.text = a.name
> default:
>     break
> }
>
> Swift currently won't allow me to use multiple value-binding patterns like
> this. I wonder what's the right way to express it? Must I repeat the
> statements?
>
> switch animal {
> case let a as Dog:
>     label.text = a.name
> case let a as Cat:
>     label.text = a.name
> default:
>     break
> }
>
> I also tried fallthrough, but swift won't let me fall through to a
> value-binding pattern:
>
> switch animal {
> case let a as Dog:
>     fallthrough // error
> case let a as Cat:
>     label.text = a.name
> default:
>     break
> }
>
> I'm at my wits end. Could someone shed some light on this? Thanks.
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-users/attachments/20170609/a3e01def/attachment.html>