Multiple accounts login in different webView in same app

Question

How i can login many accounts of same site in different webView. For example i have Tab Bar Controller That contains three View Controllers and each View Controllers contain webView. And for example i embed stackoverflow url for webView in every class. How user can login to different accounts at the same time using these three webView? I've tried this but i just login one user at a time. Can any one please tell me how this is possible in (Swift or Objective-C)?? Thanks

class FirstViewController: UIViewController , UIWebViewDelegate{

    @IBOutlet weak var webView: UIWebView!
    @IBOutlet weak var activityIndicator: UIActivityIndicatorView!

    override func viewDidLoad() {
        webView.delegate = self
        let requestURL = NSURL(string: "http://stackoverflow.com")
        let request = NSURLRequest(URL: requestURL!)
        activityIndicator.hidesWhenStopped = true
        activityIndicator.startAnimating()
        webView.loadRequest(request)

    }
       func webViewDidFinishLoad(webView: UIWebView) {
        activityIndicator.stopAnimating()
    }

}

class SecondViewController: UIViewController, UIWebViewDelegate{

    @IBOutlet weak var webView: UIWebView!
    @IBOutlet weak var activityIndicator: UIActivityIndicatorView!

    override func viewDidLoad() {
        webView.delegate = self
        let requestURL = NSURL(string: "http://stackoverflow.com")
        let request = NSURLRequest(URL: requestURL!)
        activityIndicator.hidesWhenStopped = true
        activityIndicator.startAnimating()
        webView.loadRequest(request)

    }
        func webViewDidFinishLoad(webView: UIWebView) {
        activityIndicator.stopAnimating()
    }


}