プロトコルと拡張

/*
  プロトコルと拡張
*/
protocol ExampleProtocol {
    var simpleDescription: String { get }
    mutating func adjust()
}
 
extension Int: ExampleProtocol {
    var simpleDescription: String {
      return "The number \(self)"
    }
    mutating func adjust() {
        self += 42
    }
}
 
print("7.simpleDescription = \(7.simpleDescription)")
var n : Int = 7
n.adjust()
print("n.simpleDescription = \(n.simpleDescription)")