Swift3 convert string value to hexadecimal string

Question

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?

Solution 1

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()

Solution 2

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

Comments

[vadian]

NSData is outdated in Swift 3

[dfrib]

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?

[vadian]

@dfri We know that Say Hello to My Little Friend will never fail.

[dfrib]

Is this generally true for all non-empty String instances, or do you happen to know which kind of strings that might fail?

[vadian]

Even an empty string succeeds. I don't know it for sure but I guess that any human readable text is UTF8 compatible.

[dfrib]

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" :)

[jhhoff02]

Could you include some details?