Swift - category in Swift / Extension in swift [ swift programming language apple ios]

Extension like category

“Use extension to add functionality to an existing type, such as new methods and computed properties. ”

“extension Int: ExampleProtocol {

    var simpleDescription: String {

    return "The number \(self)"

    }

    mutating func adjust() {

        self += 42

    }

}

7.simpleDescription”