11

I am new to Swift and I want to convert a string into hexadecimal string. I have found a Objective-C function to a string into hexadecimal.

NSString * str = @"Say Hello to My Little Friend";

NSString * hexString = [NSString stringWithFormat:@"%@",
[NSData dataWithBytes:[str cStringUsingEncoding:NSUTF8StringEncoding]
                                         length:strlen([str cStringUsingEncoding:NSUTF8StringEncoding])]];

for (NSString * toRemove in [NSArray arrayWithObjects:@"<", @">", @" ", nil])
    hexString = [hexString stringByReplacingOccurrencesOfString:toRemove withString:@""];

NSLog(@"hexStr:%@", hexString);

Now I am unable to convert this function in Swift. Currently I am using Swift3.

Please someone can do this for me?

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1
  • Construct a Data instance using if let strData = str.data(using: .utf8) { /* ... */ }, thereafter use the Data extension in this answer to get the data represented as a hex encoded string (let hexStr = strData.hexEncodedString()). Commented Nov 15, 2016 at 10:28

5 Answers 5

Reset to default
22

This produces the same output as the ObjC version

let str = "Say Hello to My Little Friend"
let data = Data(str.utf8)
let hexString = data.map{ String(format:"%02x", $0) }.joined()
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5 Comments

I've seen the explicit unwrapping (!) of str.data(using: .utf8) also use in other answers for String -> Data conversion. Do we know that data(..) method will never fail?
@dfri We know that Say Hello to My Little Friend will never fail.
Is this generally true for all non-empty String instances, or do you happen to know which kind of strings that might fail?
Even an empty string succeeds. I don't know it for sure but I guess that any human readable text is UTF8 compatible.
Yeah, it seems to be related to NULL return (see swift-corelibs-foundation/Foundation/NSString.swift for details) of CFStringCreateWithBytes(_:_:_:_:_:), a return case that is quite unspecied, "or NULL if there was a problem creating the object.". I have no idea what would yield a "problem creating the object" :)
8

Details

  • Xcode 11.2.1 (11B500), Swift 5.1

Solution

extension String {
    func toHexEncodedString(uppercase: Bool = true, prefix: String = "", separator: String = "") -> String {
        return unicodeScalars.map { prefix + .init($0.value, radix: 16, uppercase: uppercase) } .joined(separator: separator)
    }
}

Usage

let str = "Hello, playground"
print(str.toHexEncodedString())                                                 // 48656C6C6F2C20706C617967726F756E64
print(str.toHexEncodedString(uppercase: false, prefix: "0x", separator: " "))   // 0x48 0x65 0x6c 0x6c 0x6f 0x2c 0x20 0x70 0x6c 0x61 0x79 0x67 0x72 0x6f 0x75 0x6e 0x64
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1 Comment

Is there a way to covert it back to original string?
0

Convert your string to NSData like this.

let myString = "ABCDEF"
let data = myString.dataUsingEncoding(NSUTF8StringEncoding)

Then convert the NSData to hexadecimal string using following method -

func hexFromData(data:NSData) -> String {
    let p = UnsafePointer<UInt8>(data.bytes)
    let len = data.length
    var str: String = String()
    for i in 0...len-1 {
        str += String(format: "%02.2X", p[i])
    }
    return str
}

Hope this helped.

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1 Comment

NSData is outdated in Swift 3
0

Please try this,

let string = "Say Hello to My Little Friend"
let data = string.dataUsingEncoding(NSUTF8StringEncoding)
print(data)

and its output is:

  Optional(<53617920 48656c6c 6f20746f 204d7920 4c697474 6c652046 7269656e 64>)
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Comments

-1

Swift 3

let string = "Hello World!"
let data = string.data(using: String.Encoding.utf8)

let hexString = data?.hex


extension Data {

var hex: String {
        var string = ""

        #if swift(>=3.1)
            enumerateBytes { pointer, index, _ in
                for i in index..<pointer.count {
                    string += String(format: "%02x", pointer[i])
                }
            }
        #else
            enumerateBytes { pointer, count, _ in
                for i in 0..<count {
                    string += String(format: "%02x", pointer[i])
                }
            }
        #endif

        return string
    }


}
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1 Comment

Could you include some details?

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