Hi Chris
I do agree that it is incosistent that case works in an if but you can’t assign
it to a bool
enum Bar {
case foo(name: String)
case notFoo
case unknownFoo
}
var xx = Bar.foo(name: "Hello")
if case Bar.foo(let name) = xx where name == "Hello” { //This work ok
print("Hola")
}
var bool = case Bar.foo(let name) = xx where name == “Hello” //But this
doesn’t ???
//The other problem that I see is that the var “xx” seems to get lost int case
by having it in the middle
//I think it will be better to have an alternative keyword for a single case,
like ‘match’ that allows the variable
//to be at the begging
//This looks much better
var bool = xx match Bar.foo(let name) where name == “Hello”
Thanks
> On May 10, 2016, at 10:31 PM, Chris Lattner via swift-evolution
> <swift-evolution@swift.org> wrote:
>
>
>> On May 10, 2016, at 4:33 AM, Sam Dods via swift-evolution
>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>
>> I propose that (case .Foo = bar) should be treated as an expression with a
>> Boolean value, so the result can be set to a variable or returned from a
>> method.
>
> I agree that this is an important use case that Swift doesn’t serve well
> right now, but I don’t think this is the right way to go.
>
>> Considering the following enumeration:
>>
>> enum Bar {
>> case foo(name: String)
>> case notFoo
>> case unknownFoo
>> }
>
> One of the things we’ve discussed in the past is that we could have enums
> automatically “synthesize” instance members for projecting cases as optional
> values or bools. For example, the above enum could be compiled into the
> equivalent of:
>
> extension Bar {
> func getAsFoo() -> String? { … }
> var isNotFoo : Bool { … }
> var isUnknownFoo : Bool { … }
> }
>
> Then you could just use:
>
> if someBar.isUnknownFoo { … }
> if someBar.isFoo != nil { … }
> if let name = someBar. getAsFoo() {... }
> someBar. getAsFoo()?.doThing()
>
> etc. There is a question of naming, and getting the details right, of course.
>
> -Chris
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