Objective-C External constant property to Swift enum conversion - ios

Question

I wanted to make an enum with the Contacts framework CNLabeledValue's CNPhoneNumber type which are defined as:
// Generic labels
CONTACTS_EXTERN NSString * const CNLabelHome NS_AVAILABLE(10_11, 9_0);
CONTACTS_EXTERN NSString * const CNLabelWork NS_AVAILABLE(10_11, 9_0);
CONTACTS_EXTERN NSString * const CNLabelSchool NS_AVAILABLE(10_15, 13_0);
CONTACTS_EXTERN NSString * const CNLabelOther NS_AVAILABLE(10_11, 9_0);
I did something like this:
enum CNLabeledValueType: String {
case home
case work
case school
case other
var rawValue: String {
switch self {
case .home:
return CNLabelHome
case .work:
return CNLabelHome
case .school:
return CNLabelSchool
default:
return CNLabelOther
}
}
}
But I think I still need to do some map the enum to the correct runtime strings, do I need to also override the init of the enum somehow?
What I would like to achieve would be the same result as if this would be possible:
enum CNLabeledValueType: String {
case home = CNLabelHome
case work = CNLabelWork
case school = CNLabelSchool
case other = CNLabelOther
}
But it is not possible because Swift enums require that "Raw value for enum must be a String literal" as the compiler complains. So is there any way to make something similar using computed properties to be possible to switch by case string and also get the correct string computed value at runtime for each case?

Answer 1

You can implement init(rawValue:) like this:
init?(rawValue: String) {
switch rawValue {
case CNLabelHome:
self = .home
case CNLabelWork:
self = .work
case CNLabelSchool:
self = .school
case CNLabelOther:
self = .other
default:
return nil
}
}
Also note that you have a typo in the rawValue implementation. The second case should return CNLabelWork. I also suggest not to use default: in the raw value switch statement:
var rawValue: String {
switch self {
case .home:
return CNLabelHome
case .work:
return CNLabelWork
case .school:
return CNLabelSchool
case .other:
return CNLabelOther
}
}
This way, when you want to add a new label, an error will appear at the switch statement, so you won't forget to add another case.