What's the simplest way to convert from a single character String to an ASCII value in Swift?

edit/update Swift 5.2 or later

extension StringProtocol {
    var asciiValues: [UInt8] { compactMap(\.asciiValue) }
}

---

"abc".asciiValues  // [97, 98, 99]

---

In Swift 5 you can use the new character properties isASCII and asciiValue

Character("a").isASCII       // true
Character("a").asciiValue    // 97

Character("á").isASCII       // false
Character("á").asciiValue    // nil

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Old answer

You can create an extension:

Swift 4.2 or later

extension Character {
    var isAscii: Bool {
        return unicodeScalars.allSatisfy { $0.isASCII }
    }
    var ascii: UInt32? {
        return isAscii ? unicodeScalars.first?.value : nil
    }
}

---

extension StringProtocol {
    var asciiValues: [UInt32] {
        return compactMap { $0.ascii }
    }
}

---

Character("a").isAscii  // true
Character("a").ascii    // 97

Character("á").isAscii  // false
Character("á").ascii    // nil

"abc".asciiValues            // [97, 98, 99]
"abc".asciiValues[0]         // 97
"abc".asciiValues[1]         // 98
"abc".asciiValues[2]         // 99

UnicodeScalar("1")!.value // returns 49

Swift 3.1

Now in Xcode 7.1 and Swift 2.1

var singleChar = "a"

singleChar.unicodeScalars.first?.value