Question: I'm using Alamofire V3 with iOS 9 and I'm doing a simple request as in the README

```
Alamofire.request(.GET, WS_URL)
     .authenticate(user: user, password: password)                       
     .validate(statusCode: 200..<300)
     .responseJSON { response in
         ...
}

```

After a first valid request, I changed the credential with invalid ones and the request succeed, but it should fail.

How can I invalidate previous credentials?

`UPDATE`

I've found a possible solution but I'm not sure that it 's the best one.

```
    let plainString = "\(user):\(password)
    let plainData = plainString.dataUsingEncoding(NSUTF8StringEncoding)
    let base64String = plainData?.base64EncodedStringWithOptions(NSDataBase64EncodingOptions(rawValue: 0))
    let headers = ["Authorization": "Basic " + base64String!]
         Alamofire.request(.GET, urlRequest, headers:  headers)
        .authenticate(usingCredential: self.credential)
        .responseJSON{ responseJson in
            ...
            }

```

Thanks

Answer: 
As written in the [documentation](https://github.com/Alamofire/Alamofire#http-basic-authentication) 

*Depending upon your server implementation, an Authorization header may also be appropriate*
Assuming your endpoint is ok and they you are getting success responses...

`let` defines a constant which cannot be modified once set.

`var` defines a variable which can.

Try using a variable instead, if you've assign it compile then re-compile. Otherwise using a different name for your variable.

`print` them to see their values.