Convert NSData bytes to hexadecimal string

NSData_hexadecimalString.swift

import Foundation

extension NSData {

    /// Return hexadecimal string representation of NSData bytes
    @objc(kdj_hexadecimalString)
    public var hexadecimalString: NSString {
        var bytes = [UInt8](count: length, repeatedValue: 0)
        getBytes(&bytes, length: length)

        let hexString = NSMutableString()
        for byte in bytes {
            hexString.appendFormat("%02x", UInt(byte))
        }

        return NSString(string: hexString)
    }
}

let bytes = UnsafePointer<UInt8>(self.bytes)

It's not necessary to copy the bytes.

@ast UnsafePointer does not conform to SequenceType

Or simply with one line return self.map{ String(format: "%02x", $0) }.joined()