How to convert String to byte in Swift？

Question

How to convert String to byte in Swift？ Like String .getBytes()in Java.

possible duplicate of [How to convert NSString to bytes](http://stackoverflow.com/questions/881482/how-to-convert-nsstring-to-bytes) — ahruss, Jul 30 '14 at 02:31

score 128 · Answer 1 · edited Dec 19 '17 at 15:33

128

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)

edited Dec 19 '17 at 15:33

derpoliuk

answered Sep 19 '14 at 11:29

Albin Stigo

I don't know why I put in `var buf`, might as well be `let buf` – Albin Stigo Jun 10 '15 at 20:54
Definitely the best way. – JeremyP Aug 02 '15 at 15:32
5

Apparently not working in Swift 4. Use `var buf : [UInt8] = Array(str.utf8)` instead. – PJ_Finnegan Oct 16 '17 at 13:13

Connor Pearson · Accepted Answer · 2014-10-16T02:11:41.667

18

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)

edited Oct 16 '14 at 02:11

answered Jul 30 '14 at 02:34

Connor Pearson

2

[(Byte)] is not identical to to 'UInt8' – xaxxon Oct 14 '14 at 18:50
@xaxxon in what way is it not? – Joe Daniels Oct 23 '16 at 02:07
3

@JoeDaniels I have no clue. I'm not even sure I wrote that. – xaxxon Oct 23 '16 at 19:07

Leo Dabus · Answer 3 · 2020-06-17T14:44:23.600

13

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]

edited Jun 17 '20 at 14:44

answered Feb 25 '15 at 11:02

Leo Dabus

score 3 · Answer 4 · answered Aug 02 '14 at 10:45

3

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)")
}

answered Aug 02 '14 at 10:45

hnh

score 2 · Answer 5 · answered Feb 23 '15 at 22:28

2

Another option, for when you need to be able to pass to C-library functions:

let str = hexColour.cStringUsingEncoding(NSUTF8StringEncoding)
let x = strtol(str!, nil, 16)

answered Feb 23 '15 at 22:28

Chris

score 1 · Answer 6 · answered Jul 30 '14 at 02:31

1

answered Jul 30 '14 at 02:31

carloabelli

score 1 · Answer 7 · answered May 08 '18 at 13:10

Swift 4.1.

It depends what you want to achieve. For the same question, I used...

let message = "Happy"
for v in message.utf8 {
    print(v)
}

I then performed the operations I needed on the individual byte. The output is:

//72
//97
//112
//112
//121

7 Answers7