Distinction in Swift between uppercase “Self” and lowercase “self”

Question

While playing in a Swift playground I noticed that Self, with capital \"S\", is available along with the lowercase self. Is there any difference be

Answer 1

Self can also be used as a return type in the protocol extension method body which will return confirming type instance, and for type casting with "as". Please see example below:

extension  where Self: {
static func foo(_ param:Type)-> Self{
    guard let abc = method() as? Self else{
        return xyz
    }
}}

In the nutshell, Self can be used to refer the Type which confirms to the protocol.