How to convert String to byte in Swift？

String.withCString is the peer to Java's String.getBytes(void). Use it like this (extra typing added):

let s = "42"
s.withCString {
  ( bytes : (UnsafePointer<CChar>) ) -> Void in
  let k = atoi(bytes)
  println("k is \(k)")
}

edit/update: Xcode 11.5 • Swift 5.2

extension StringProtocol {
    var data: Data { .init(utf8) }
    var bytes: [UInt8] { .init(utf8) }
}

"12345678".bytes   // [49, 50, 51, 52, 53, 54, 55, 56]

You can iterate through the UTF8 code points and create an array:

var str = "hello, world"
var byteArray = [Byte]()
for char in str.utf8{
    byteArray += [char]
}
println(byteArray)

There is a more elegant way.

Swift 3:

let str = "Hello"
let buf = [UInt8](str.utf8)

Swift 4: (thanks to @PJ_Finnegan)

let str = "Hello"
let buf: [UInt8] = Array(str.utf8)

Related