Given a hexadecimal string in Swift, convert to hex value

Question

Suppose I am given a string like this:

D7C17A4F

How do I convert each individual character to a hex value?

So D

Answer 1

here is the more generic, "pure swift" approach (no Foundation required :-))

extension UnsignedInteger {
    var hex: String {
        var str = String(self, radix: 16, uppercase: true)
        while str.characters.count < 2 * MemoryLayout.size {
            str.insert("0", at: str.startIndex)
        }
        return str
    }
}

extension Array where Element: UnsignedInteger {
    var hex: String {
        var str = ""
        self.forEach { (u) in
            str.append(u.hex)
        }
        return str
    }
}

let str = [UInt8(1),22,63,41].hex  // "01163F29"
let str2 = [UInt(1),22,63,41].hex  // "00000000000000010000000000000016000000000000003F0000000000000029"

extension String {
    func toUnsignedInteger()->[T]? {
        var ret = [T]()
        let nibles = MemoryLayout.size * 2
        for i in stride(from: 0, to: characters.count, by: nibles) {
            let start = self.index(startIndex, offsetBy: i)
            guard let end = self.index(start, offsetBy: nibles, limitedBy: endIndex),
                let ui = UIntMax(self[start..

It is very easily to do the same for SignedInteger as well, but better approach will be to map results to signed type

let u8 = u1?.map { Int8(bitPattern: $0) }                    // [-14, 52, 95]