Unable to convert string... to string in Swift

I'm trying to make a simple debuger in a view.. and I have the following:

I'm using Alamofire to make the request, receiving the data with responseString and then sending it with App.log( response ) towards debugViewController's logmethod which as you can see expects a string as well.

Now, trying to compile this returns an error which is very weird for me as I'm new to Swift. Cannot convert string to the argument type expected in debugViewController.log() which is in fact String as well ?

Please enlight me on this one.

Here you have the debugViewController:

import UIKit

class debugViewController: UIViewController {

    @IBOutlet weak var debugTextField: UITextView!

    @IBAction func dismissDebug(sender: AnyObject) {
        self.dismissViewControllerAnimated(true, completion: nil)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

     func log( data: String ) {
        debugTextField.text = data
    }

}

And here you can see how I make the call and send data:

Alamofire.request( .POST, API_URL, parameters: [ "action": "authenticate", "email": userEmail!, "password": userPassword! ] )
            .responseString { response in

                guard let value = response.result.value else
                {
                    return App.alert( "error", message: "Did not receive data")
                }

                guard response.result.error == nil else
                {
                    print( response.result.error )
                    return App.alert( "error", message: "An error occurred" )
                }

                App.log ( value )


        }