Many styles of programming can take advantage of if/else and switch/case being actual expressions (actually, these are all special cases of the very general concept of "folding"). We don't have this in Swift, and I have occasion to be bothered by this almost on a daily basis in my work, especially when I try to be "concise", something for which Swift should be champion.
The best possible outcome would be for Swift to have pattern matching as a proper evaluated expression, but I would accept a new operator that takes advantage of some custom compiler magic, because the use cases are so many and the convenience would be so great. As Colin Barret said, this is a very popular thing in many modern languages. Elviro > Il giorno 20 dic 2017, alle ore 19:32, Colin Barrett via swift-evolution > <swift-evolution@swift.org> ha scritto: > > This would be easily solved if pattern matching was available as an > expression, such as in Haskell, OCaml / Standard ML, and Scala / Kotlin. :-) > >> On Dec 20, 2017, at 11:44 AM, Ethan Diamond via swift-evolution >> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >> >> Hello everyone, >> >> One major pain point I've run into with Swift is the inability to evaluate >> the case of an enum that has associated values in a way that just returns a >> bool. We've been given the ability in a switch statement: >> >> enum Enum { >> case a(param: String) >> case b(param: String) >> } >> >> let enumeration: Enum = a(param: "Hi") >> switch enumeration { >> case a: >> // Do something >> case b: >> // Do something >> } >> >> We'e been given the ability in the context of an if statement: >> >> enum Enum { >> case a(param: String) >> case b(param: String) >> } >> >> let enumeration: Enum = a(param: "Hi") >> >> if case .a = enumeration { >> // Do something >> } >> >> But without a basic was of getting a bool for if an enum is a given case, >> here's a list of things I can't do: >> >> Where statements: >> >> enum Enum { >> case a(param: Enum2) >> case b(param: Enum2) >> } >> >> enum Enum2 { >> case c(param: String) >> case d(param: String) >> } >> >> let enumeration: Enum = a(param: "Hi") >> switch enumeration { >> case a(let inner) where [INNER CASE IS .c] >> } >> >> --------- >> >> Filter an array for a certain case: >> >> Expertly explained by Erica Sadun here: >> http://ericasadun.com/2017/01/31/challenge-filtering-associated-value-enumeration-arrays/ >> >> <http://ericasadun.com/2017/01/31/challenge-filtering-associated-value-enumeration-arrays/> >> >> --------- >> >> Nicely set a UIButton to hidden if an enum is a certain case: >> >> enum State { >> case `default` >> case searching(results: [Result]) >> } >> >> myButton.isHidden = [STATE IS .searching] >> >> --------- >> >> I've run into this issue a ton of times because I tend to represent my views >> a State enums. I haven't seen anything on the board for plans for solving >> this issue, thought. Has there been any discussion about addressing it? >> Ideally I'd be able to do this: >> >> enum Enum { >> case a(param: String) >> case b(param: String) >> } >> >> let enumeration: Enum = a(param: "Hi") >> >> case .a = enumeration // Bool >> case .a(let param) = enumeration // Bool, assigns "Hi" to "param" >> >> Thanks! >> Ethan >> >> _______________________________________________ >> swift-evolution mailing list >> swift-evolution@swift.org <mailto:swift-evolution@swift.org> >> https://lists.swift.org/mailman/listinfo/swift-evolution > > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
_______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
