     
     private var webView = UIWebView()
     
-    private var authorizationURL: String!
-    private var callbackURL: String!
+    private var authorizationURLString: String!
+    private var callbackURLString: String!
+
+    private var authorizationURL: NSURL {
+        get {
+            return NSURL(string: authorizationURLString)!
+        }
+    }
+    private var callbackURL: NSURL {
+        get {
+            return NSURL(string: callbackURLString)!
+        }
+    }
     
     private var successBlock: FlickrOAuthViewControllerSuccessCompletionHandler!
     private var failureBlock: FlickrOAuthViewControllerFailureCompletionHandler!

    // MARK: Init
    
    init(authorizationURL: String, callbackURL: String) {
        self.authorizationURL = authorizationURL
        self.callbackURL = callbackURL
        super.init(nibName: nil, bundle: nil)
    }
    

        webView.autoresizingMask = UIViewAutoresizing(arrayLiteral: .FlexibleWidth, .FlexibleHeight)
        view.addSubview(webView)
        
        let request = NSURLRequest(URL: authorizationURL)
        webView.loadRequest(request)
        
        let doneBarButtonItem = UIBarButtonItem(barButtonSystemItem: .Done, target: self, action: #selector(dismiss))
