Creating NSData from NSString in Swift

Question

I'm trying to ultimately have an NSMutableURLRequest with a valid HTTPBody, but I can't seem to get my string data (coming from a UITextField) into a usable NSData object.

I've seen this method for going the other way:

NSString(data data: NSData!, encoding encoding: UInt)

But I can't seem to find any documentation for my use case. I'm open to putting the string into some other type if necessary, but none of the initialization options for NSData using Swift seem to be what I'm looking for.

Gabriele Petronella · Accepted Answer · 2016-08-22T09:37:29.167

371

In Swift 3

let data = string.data(using: .utf8)

In Swift 2 (or if you already have a NSString instance)

let data = string.dataUsingEncoding(NSUTF8StringEncoding)

In Swift 1 (or if you have a swift String):

let data = (string as NSString).dataUsingEncoding(NSUTF8StringEncoding)

Also note that data is an Optional<NSData> (since the conversion might fail), so you'll need to unwrap it before using it, for instance:

if let d = data {
    println(d)
}

edited Aug 22 '16 at 09:37

answered Jun 04 '14 at 14:16

Gabriele Petronella

106,943
21
217
235

Swift can infer NSData type? – Nicolas Manzini Jun 04 '14 at 14:18
@NicolasManzini sure it can, as with any other type. – Gabriele Petronella Jun 04 '14 at 14:18
`Value of optional type 'NSData?' not unwrapped; did you mean to use '!' or '?'?` – User Sep 20 '14 at 22:37
2

@macdonjo yep, that API changed over time and now it returns an `Optional`, which you need to unwrap before using – Gabriele Petronella Sep 21 '14 at 16:57
@GabrielePetronella In which case its probably cleaner to just use `if let data = (swiftString as NSString).dataUsingEncoding(NSUTF8StringEncoding){}` to handle the conversation and optional all at once. – memmons Jun 08 '15 at 00:29
3

In Swift2, there's no need to use "as" cast since it's automatically bridged – LiangWang Jun 18 '15 at 01:51
1

A conversion to UTF-8 *cannot* fail, therefore an optional binding it not really needed, you can force-unwrap here. – Martin R Aug 25 '16 at 06:52
In Swift 3+ there is a better way: `Data(string.utf8)`. The benefit is that the result is non-optional. – vadian Nov 21 '18 at 07:56

Said Sikira · Answer 2 · 2017-06-07T12:13:51.427

34

Swift 4 & 3

Creating Data object from String object has been changed in Swift 3. Correct version now is:

let data = "any string".data(using: .utf8)

edited Jun 07 '17 at 12:13

answered Aug 19 '16 at 13:12

Said Sikira

4,482
29
42

Thanks. This worked for me in swift 3 perfectly. let input = "test string" let xdata = input.data(using: String.Encoding.utf8) – raddevus Oct 02 '16 at 15:59
1

Any idea why String(data: data!, encoding: .nonLossyASCII) will be nil? – Happiehappie Oct 13 '16 at 06:53

score 6 · Answer 3 · edited May 01 '19 at 19:05

6

In swift 5

let data = Data(YourString.utf8)

edited May 01 '19 at 19:05

oguz ismail

1
16
47
69

answered May 01 '19 at 18:43

Sanjay Mishra

672
7
17

score 4 · Answer 4 · answered Oct 30 '14 at 08:42

4

Here very simple method

let data = string.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)

answered Oct 30 '14 at 08:42

Shafraz Buhary

643
6
14

score 4 · Answer 5 · edited May 18 '18 at 12:53

4

Swift 4

let data = myStringVariable.data(using: String.Encoding.utf8.rawValue)

edited May 18 '18 at 12:53

TheTiger

13,264
3
57
82

answered Mar 06 '18 at 04:41

jatin

181
7

Don't use `NSString` in Swift. – vadian Nov 21 '18 at 07:57

score 4 · Answer 6 · answered Apr 01 '20 at 14:32

Convert String to Data

extension String {
    func toData() -> Data {
        return Data(self.utf8)
    }
}

Convert Data to String

extension Data {
      func toString() -> String {
          return String(decoding: self, as: UTF8.self)
      }
   }

score 3 · Answer 7 · answered Nov 05 '14 at 06:42

// Checking the format
var urlString: NSString = NSString(data: jsonData, encoding: NSUTF8StringEncoding)

// Convert your data and set your request's HTTPBody property
var stringData: NSString = NSString(string: "jsonRequest=\(urlString)")

var requestBodyData: NSData = stringData.dataUsingEncoding(NSUTF8StringEncoding)!

score 3 · Answer 8 · answered Nov 21 '18 at 07:24

3

To create not optional data I recommend using it:

let key = "1234567"
let keyData = Data(key.utf8)

answered Nov 21 '18 at 07:24

Ramis

13,985
7
81
100

2

In Swift 3+ this is the most efficient way. – vadian Nov 21 '18 at 07:52

score 3 · Answer 9 · answered Jan 09 '19 at 14:28

3

Swift 4.2

let data = yourString.data(using: .utf8, allowLossyConversion: true)

answered Jan 09 '19 at 14:28

meMadhav

233
2
12

Creating NSData from NSString in Swift

9 Answers9

Swift 4 & 3

Linked

Related