Am 11. Mai 2016 um 05:31 schrieb Chris Lattner via swift-evolution
<swift-evolution@swift.org>:
On May 10, 2016, at 4:33 AM, Sam Dods via swift-evolution
<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()
I would strongly prefer pattern matching over magic methods, because of the
following reasons:
(a) IMHO the latter are confusing because it is not clear and visible which
methods have been created
(b) patterns allow IDE support for browsing usages of the various enums whereas
browsing for a bunch of invisible automagically created methods is much more
difficult and confusing
(c) I can't see a way of generating nice methods for accessing associated
values (in various combinations) (see getAsFoo() example above and imagine a
second or third parameter to Bar.foo)
-Thorsten
etc. There is a question of naming, and getting the details right, of course.
-Chris
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