对象可见的字符串枚举，但不是RawRepresentable

Question

I want to use enum that is visible both in objective C and Swift but not conform to protocol RawRepresentable.

1. I tried to have an enum of string both visible in Objc and Swift thus I use

   typedef NSString *myEnum NS_TYPED_ENUM;

2. I tried to take advantage of the myEnum(rawValue: ) -> myEnum? function but I found the enumType has automatically conform to

   public struct myEnum : Hashable, Equatable, RawRepresentable { public init(rawValue: String) }

My question is how to create enum that is visiable in Objc and Swift but not conform to this protocol? Thanks for all the help!

Answer 1

Swift Language Enhancements

... Swift enums can now be exported to Objective-C using the @objc attribute. @objc enums must declare an integer raw type, and cannot be generic or use associated values. Because Objective-C enums are not namespaced, enum cases are imported into Objective-C as the concatenation of the enum name and case name.

Above From Xcode 6.4 Release Notes

---

For this purpose you define the values in Objective-C, you can use the NS_TYPED_ENUM macro to import constants in Swift For example: .h file

typedef NSString *const ProgrammingLanguage NS_TYPED_ENUM;

FOUNDATION_EXPORT ProgrammingLanguage ProgrammingLanguageSwift;
FOUNDATION_EXPORT ProgrammingLanguage ProgrammingLanguageObjectiveC;

.m file

ProgrammingLanguage ProgrammingLanguageSwift = "Swift";
ProgrammingLanguage ProgrammingLanguageObjectiveC = "ObjectiveC";

In Swift, this is imported as a struct as such:

struct ProgrammingLanguage: RawRepresentable, Equatable, Hashable {
    typealias RawValue = String

    init(rawValue: RawValue)
    var rawValue: RawValue { get }

    static var swift: ProgrammingLanguage { get }
    static var objectiveC: ProgrammingLanguage { get }
}

Although the type is not bridged as an enum, it feels very similar to one when using it in Swift code.

You can read more about this technique in the " Interacting with C APIs " of the Using Swift with Cocoa and Objective-C documentation