在 appDelegate.m 里的 didFinishLaunchingWithOptions

//authenticatedUser: 檢查 NSUserDefaults 里的用戶證書，如果存在就根據(jù)它設(shè)置導(dǎo)航流程

if (authenticatedUser) 
{
    self.window.rootViewController = [[UIStoryboard storyboardWithName:@"Main" bundle:[NSBundle mainBundle]] instantiateInitialViewController];        
}
else
{
    UIViewController* rootController = [[UIStoryboard storyboardWithName:@"Main" bundle:[NSBundle mainBundle]] instantiateViewControllerWithIdentifier:@"LoginViewController"];
    UINavigationController* navigation = [[UINavigationController alloc] initWithRootViewController:rootController];

    self.window.rootViewController = navigation;
}

在 SignUpViewController.m 文件

- (IBAction)actionSignup:(id)sender
{
    AppDelegate *appDelegateTemp = [[UIApplication sharedApplication]delegate];

    appDelegateTemp.window.rootViewController = [[UIStoryboard storyboardWithName:@"Main" bundle:[NSBundle mainBundle]] instantiateInitialViewController];
}

在 MyTabThreeViewController.m 文件

- (IBAction)actionLogout:(id)sender {

    // 從 NSUserDefaults 中刪除用戶證書，以及其他用戶相關(guān)數(shù)據(jù)

    AppDelegate *appDelegateTemp = [[UIApplication sharedApplication]delegate];

    UIViewController* rootController = [[UIStoryboard storyboardWithName:@"Main" bundle:[NSBundle mainBundle]] instantiateViewControllerWithIdentifier:@"LoginViewController"];

    UINavigationController* navigation = [[UINavigationController alloc] initWithRootViewController:rootController];
    appDelegateTemp.window.rootViewController = navigation;

}