Unable to call a function with a Codable Generic Parameter - swift

Question

I have a class that takes a generic parameter T class CacheRepository<T> {}that contains a func transform(). In which I need to call another function with the following signature func transformCodable<U: Codable>(ofType: U.Type)-- if T conforms to Codable protocol. But I failed to do so. Below are my trials with their compilation errors.
Trial 1:
func transform() {
if T.self is Codable.Type {
// Error: In argument type 'CacheRepository<T>.T.Type' (aka 'T.Type'), 'T' does not conform to expected type 'Decodable'
sharedStorage!.transformCodable(ofType: T.self)
}
}
Trial 2:
func transform() {
if T.self is Codable.Type {
//Cannot invoke 'transformCodable' with an argument list of type '(ofType: (Codable))'
//Expected an argument list of type '(ofType: U.Type)'
sharedStorage!.transformCodable(ofType: (T as! Codable).self)
}
}
Trial 3: I tried to extend CacheRepository class if T is Codable, but the extension transform function never gets called, when called in the init() function. And if I called it after the instance is created, it doesn't get called in all cases.
class CacheRepository<T> {
func transform() {
print("non-codable transform")
}
}
extension CacheRepository where T: Codable {
func transform() {
sharedStorage!.transformCodable(ofType: T.self)
}
}
example: This works
let transform = CacheRepository<Int>().transform()
But if I added a shared instance inside the CacheRepository class, and tried to call transform after instantiation, it doesn't get called. And the really odd this is, if I called the tranform on the new instance in console the right transform is called.

Answer 1

How is this?
extension CacheRepository where T: Codable {
func transform() {
print("Codable")
sharedStorage!.transformCodable(ofType: T.self)
}
}
extension CacheRepository {
func transform() {
print("Non-codable")
}
}
This worked as expected in a very simplified CacheRepository. But not sure if it works in your actual CacheRepository, please try.