Extension for String enum implementing CaseIterable Swift 4 - swift4

Question

From swift 4 the protocol CaseIterable in enums has made my life happier but I would like to know if I can create an extension for an enum Type:String,CaseIterable.
So far I can create an enum String extension like that:
extension RawRepresentable where RawValue == String{
func toCorrectFormatSring()->String{
var returnedString = self.rawValue
returnedString = returnedString.uppercased()
return returnedString
}
}
But I have some enums that have a common function and I don't want to repeat it in all the enums. The function gives all the cases in a coma separated string and it looks like that:
enum Vehicle:String,CaseIterable{
case car
case truck
static func getStringList()->String{
let aArray = self.allCases
var returnedString = ""
for aItem in aArray{
returnedString += "\(aItem.toCorrectFormatSring())\(aItem == aArray.last ? "":",")"
}
return returnedString
}
}
The function I want to use wit the extension is getStringList. Is it possible?
OUPUT
[CAR,TRUCK]

Answer 1

You probably want something like this:
extension RawRepresentable where RawValue == String {
func toCorrectFormat() -> String {
let returnedString = // whatever
return returnedString
}
}
extension CaseIterable where Self : RawRepresentable, Self.RawValue == String {
static func getStringList() -> String {
let aArray = Array(self.allCases)
var returnedString = ""
if let last = aArray.last {
for aItem in aArray{
returnedString += "\(aItem.toCorrectFormat())\(aItem == last ? "" : ",")"
}
}
return returnedString
}
}
Now you're good to go, because the protocol extension injects the desired static function into the enum:
enum E : String, CaseIterable {
case howdy
case byebye
}
let s = E.getStringList()
Now that you know how to inject the desired functionality, you can rewrite getStringList in a much better way (the loop is silly, the comparison with last is wrong, and the string interpolation is unnecessary). I think what you're really after is something like this:
extension CaseIterable where Self : RawRepresentable, Self.RawValue == String {
static func getStringList() -> String {
return Array(self.allCases)
.map{$0.rawValue.uppercased()}
.joined(separator:",")
}
}