Generating HMAC-SHA256 from Byte-Array in Swift - xcode

Question

I want to create a signature for the myJD REST-API. But the first snippet is not working. I talked to the support and they told me that I need the unhexed key to create the correct hash. So I created a Byte-Array of the Hex-Value and changed the code to work again (see second snippet). Both methods have the same result.
Link to API documentation: https://docs.google.com/document/d/1IGeAwg8bQyaCTeTl_WyjLyBPh4NBOayO0_MAmvP5Mu4/edit?pref=2&pli=1
First:
import Foundation
extension String{
func hmacSHA256(key: String) -> String {
let str = self.cStringUsingEncoding(NSUTF8StringEncoding)
let strLen = Int(self.lengthOfBytesUsingEncoding(NSUTF8StringEncoding))
let digestLen = Int(CC_SHA256_DIGEST_LENGTH)
let result = UnsafeMutablePointer<CUnsignedChar>.alloc(digestLen)
let keyStr = key.cStringUsingEncoding(NSUTF8StringEncoding)!
let keyLen = Int(key.lengthOfBytesUsingEncoding(NSUTF8StringEncoding))
CCHmac(CCHmacAlgorithm(kCCHmacAlgSHA256), keyStr, keyLen, str!, strLen, result)
let digest = stringFromResult(result, length: digestLen)
result.dealloc(digestLen)
return digest
}
private func stringFromResult(result: UnsafeMutablePointer<CUnsignedChar>, length: Int) -> String {
let hash = NSMutableString()
for i in 0..<length {
hash.appendFormat("%02x", result[i])
}
return String(hash)
}
}
Second:
func hmacSHA256_2(key: String) -> String {
//let cKey = key.dataUsingEncoding(NSUTF8StringEncoding)!
let bKey = Array(key.utf8)
let bData = Array(self.utf8)
//let cData = self.dataUsingEncoding(NSUTF8StringEncoding)!
var cHMAC = [CUnsignedChar](count: Int(CC_SHA256_DIGEST_LENGTH), repeatedValue: 0)
CCHmac(CCHmacAlgorithm(kCCHmacAlgSHA256), bKey, Int(bKey.count), bData, Int(bData.count), &cHMAC)
let output = NSMutableString(capacity: Int(CC_SHA256_DIGEST_LENGTH))
for byte in cHMAC {
output.appendFormat("%02hhx", byte)
}
return output as String
}