Is there a way to use the 'is' type check operator with RandomAccessCollection?

Question

I'm getting the following error on the 'if' condition:

"Protocol 'RandomAccessCollection' can only be used as a generic constraint because it has Self or associated type requirements"

let str = "mystring"

let v = str.utf8

if v is RandomAccessCollection {
    print("YES")
} else {
    print("NO")
}

Out of curiosity, is there a way to use the "is" type check operator to check if an object/instance conforms to RandomAccessCollection?

Answer 1

These type checks at runtime are unswifty. Don't do that.

A possible way is method overloading, the check is performed at compile time for example

func checkType<T>(obj: T) {
    print("NO")
}

func checkType<T:RandomAccessCollection>(obj: T) {
    print("YES")
}

let str = "mystring"
let v = str.utf8
checkType(obj: v) // prints NO

let x = Data(v)
checkType(obj: x)  // prints YES

If the object conforms to the protocol the second method is called otherwise the first.