Converting to Char/String from Ascii Int in Swift

Question

I'm trying to convert the integer representation of an ascii character back into a string.

string += (char) int;

In other languages like Java (the example here) I can just cast the integer into a char. Swift obviously does not know these and I'm guessing using the all powerful NSString somehow will be able to do the trick.

Answer 1

It may not be as clean as Java, but you can do it like this:

var string = ""
string.append(Character(UnicodeScalar(50)))

You can also modify the syntax to look more similar if you like:

//extend Character so it can created from an int literal
extension Character: IntegerLiteralConvertible {
    public static func convertFromIntegerLiteral(value: IntegerLiteralType) -> Character {
        return Character(UnicodeScalar(value))
    }
}

//append a character to string with += operator
func += (inout left: String, right: Character) {
    left.append(right)
}

var string = ""
string += (50 as Character)

Or using dasblinkenlight's method:

func += (inout left: String, right: Int) {
    left += "\(UnicodeScalar(right))"
}
var string = ""
string += 50

Answer 2

Here's a production-ready solution in Swift 3:

extension String {
    init(unicodeScalar: UnicodeScalar) {
        self.init(Character(unicodeScalar))
    }


    init?(unicodeCodepoint: Int) {
        if let unicodeScalar = UnicodeScalar(unicodeCodepoint) {
            self.init(unicodeScalar: unicodeScalar)
        } else {
            return nil
        }
    }


    static func +(lhs: String, rhs: Int) -> String {
        return lhs + String(unicodeCodepoint: rhs)!
    }


    static func +=(lhs: inout String, rhs: Int) {
        lhs = lhs + rhs
    }
}

Usage:

let a = String(unicodeCodepoint: 42) // "*"
var b = a + 126 // "*~"
b += 33 // "*~!"

Note that this works with all ASCII and Unicode codepoints, so you can do this:

var emoji = String(unicodeCodepoint: 0x1F469)! // "👩"
emoji += 0x200D // "👩‍"
emoji += 0x1F4BB // "👩‍💻"

---

As a personal note, I wouldn't use this in my code. I would have expected ":" + 40 to become ":40", not ":(". If you prefer the second one where 40 becomes "(", then this should work well for you :)

Answer 3

If you want only String characters from A... you can use this func:

func characterFromInt(index : Int) -> String {
        let startingValue = Int(("A" as UnicodeScalar).value)
        var characterString = ""
        characterString.append(Character(UnicodeScalar(startingValue + index)))
        return characterString
    }