Retrieve SecKey from Keychain

Question

I am trying to upgrade the code that I got from this answer for generating CSR, from Swift 2 to Swift 3.

I have most of the code upgraded, but the following code in the

Answer 1

Just use SecItemCopyMatching. I was able to convert it to Swift 3 and successfully generate CSR.

// Finds the SecKeyRef corresponding to the parameter key and returns it
func loadKeySecKeyFromKeyChain(key: String) -> SecKey {
    let query: Dictionary<String, AnyObject> = [
        String(kSecAttrKeyType): kSecAttrKeyTypeRSA,
        String(kSecAttrKeySizeInBits): KEY_SIZE as AnyObject,
        String(kSecClass): kSecClassKey,
        String(kSecAttrApplicationTag): key as AnyObject,
        kSecReturnRef as String : kCFBooleanTrue ]

    var dataTypeRef: Unmanaged<AnyObject>? = nil
    var resultData: SecKey? = nil
    var result: AnyObject?
    let status = SecItemCopyMatching(query as CFDictionary, &result)

    if status == errSecSuccess {
        resultData = result as! SecKey
        return resultData!
    } else {
        return resultData!
    }
}