Type conversion when using protocol in Swift

Question

protocol Test{

    var t: Int {set get}

}

struct A: Test{

    var t: Int

}

struct B: Test{

    var t: Int
    var s: String

}

let a = A(t: 1)
let b = B(t: 2         


        

Answer 1

You cannot convert an array wholesale like that. Use map:

let f = e.map { $0 as Test } // f is now a [Test] array