Swiftは同じ関数名でも引数が異なれば宣言できる

struct User {
    
    func decorate(a: String) -> String {
        return "+++" + a + "+++"
    }
    
    func decorate(a: String, b: String) -> String {
        let a = self.decorate(a:a)
        let b = self.decorate(a:b)
        return a + ":" + b
    }
}

let user = User()
let str = user.decorate(a:"a", b:"b")
print(str)