String-interpolation

adding-score.swift

var bobScore = "Bob has a score of \(2 * 3)"

basic-swift-string-interpolation.swift

let currentScore = 10
let userScore = "User has a score of \(currentScore)"

custom-string-interpolation.swift

struct User {
    var userName: String
    var score: Int
}

extension String.StringInterpolation {
    mutating func appendInterpolation(user: User) {
        appendInterpolation("User \(user.userName) has a score of \(user.score)")
    }
}

let ben = User(userName: "Ben10", score: 2)
print("\(user: ben)") ///User Ben10 has a score of 2