I am creating the iOS Native app in which I am customizing the Login page to look like Salesforce1 iOS app page. It also includes a Settings button which allows user to switch to a different endpoint URL using a dropdown.

I was successful in creating a cutomized page, loading the Login screen and authenticating the user.
 
My problem is that when I switch the endpoint URL to say Sandbox(by default the app is pointing to Production), using the Settings dropdown using the below code.

[[SFUserAccountManager sharedInstance] setLoginHost:loginHost];

and reload the UIWebView Login page again using the below code, it does not set the endpoint that I had selected from the dropdown.

SFAuthenticationViewHandler *authHandler = [[SFAuthenticationViewHandler alloc]
                                                initWithDisplayBlock:^(SFAuthenticationManager *authManager, UIWebView *authWebView) {
                                                    //authController is the custom ViewContoller which has the UIWebView and in this block I am asigning the webview recevied from the SFDC SDK.
                                                    authController.authViewCompleted = NO;
                                                    authController.authWebView = authWebView;
                                                    authWebView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
                                                    authWebView.frame = authController.webViewHolder.bounds;
                                                    [rootViewController presentViewController:authController animated:TRUE completion:nil];
                                                } dismissBlock:^(SFAuthenticationManager *authViewManager) {
                                                    authController.authViewCompleted = TRUE;
                                                    [authController dismissViewControllerAnimated:TRUE completion:nil];
                                                }];
    
    _notificationNameDictionary = @{kSFUserLogoutNotification : kPSSUserLogoutNotification,
                                    kSFUserLoggedInNotification : kPSSUserLoggedInNotification,
                                    kSFLoginHostChangedNotification : kPSSLoginHostChangedNotification};
    
    self.authManager.authViewHandler = authHandler;
    [self.authManager loginWithCompletion:completionBlock failure:failureBlock];

I know for sure that the Sandbox endpoint is set, because when I kill the app and reopen it then the Login Page is loading the Sandbox login page.

I want to know how would I be able to replicate the Settings behavior to take the Sandbox endpoint at runtime, and not the Production endpoint(default one) without letting the user to kill the application.