Swift Covariant Generics

Question

Here is an example of what I\'d like to achieve:

protocol SomeType {}

class SomeClass: SomeType {}

struct SomeGenericStruct {
    typealias E = A
         


        

Answer 1

You can use generic method for this:

func take<T where T: SomeType>(someType: SomeGenericStruct<T>) { }

The only problem with this is that you can not pass SomeGenericStruct<SomeType> to it. It must be a generic of some concrete type instead. If totally necessary, you can just have two functions doing the same thing essentially:

func take(someInput: SomeGenericStruct<SomeType>) { /* do stuff */ }
func take<T where T: SomeType>(someType: SomeGenericStruct<T>) { /* do same stuff */ }