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.

Ruscio

Answer 1

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)
}

Wireman

Swift can infer NSData type? – Variegation

@NicolasManzini sure it can, as with any other type. – Wireman

Value of optional type 'NSData?' not unwrapped; did you mean to use '!' or '?'? – Deenadeenya

@macdonjo yep, that API changed over time and now it returns an Optional<NSData>, which you need to unwrap before using – Wireman

@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. – Deuced

In Swift2, there's no need to use "as" cast since it's automatically bridged – Hyacinthus

A conversion to UTF-8 cannot fail, therefore an optional binding it not really needed, you can force-unwrap here. – Feverous

In Swift 3+ there is a better way: Data(string.utf8). The benefit is that the result is non-optional. – Individualize

Answer 2

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)

Vandiver

Thanks. This worked for me in swift 3 perfectly. let input = "test string" let xdata = input.data(using: String.Encoding.utf8) – Stricture

Any idea why String(data: data!, encoding: .nonLossyASCII) will be nil? – Couple

Answer 3

In swift 5

let data = Data(YourString.utf8)

Idalia

Answer 4

Here very simple method

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

Sepaloid

Answer 5

Swift 4

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

Chesterfield

Don't use NSString in Swift. – Individualize

Answer 6

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)
      }
   }

Zigrang

Answer 7

// 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)!

Thoughtless

Answer 8

To create not optional data I recommend using it:

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

Charlton

In Swift 3+ this is the most efficient way. – Individualize

Answer 9

Swift 4.2

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

Ardehs