Ios – Presenting a modal controller without knowing the current view controller

iosmodal-dialogpresentmodalviewcontroller

Is there a way to present a view controller modally without knowing what the visible view controller view is? Basically sort of like you would show an alert view at any points in time.

I would like to be able to do something like:

MyViewController *myVC = [[MyViewController alloc] init];
[myVC showModally];

I'd like to be able to call this from anywhere in the app, and have it appear on top. I don't want to care about what the current view controller is.

I plan to use this to show a login prompt. I don't want to use an alert view, and I also don't want to have login presentation code throughout the app.

Any thoughts on this? Or is there maybe a better way to achieve this? Should I just implement my own mechanism and just place a view on top of the window?

Best Answer

Well, you can follow the chain.

Start at [UIApplication sharedApplication].delegate.window.rootViewController.

At each view controller perform the following series of test.

If [viewController isKindOfClass:[UINavigationController class]], then proceed to [(UINavigationController *)viewController topViewController].

If [viewController isKindOfClass:[UITabBarController class]], then proceed to [(UITabBarController *)viewController selectedViewController].

If [viewController presentedViewController], then proceed to [viewController presentedViewController].

Related Solutions

Ios – presentViewController and displaying navigation bar

It is true that if you present a view controller modally on the iPhone, it will always be presented full screen no matter how you present it on the top view controller of a navigation controller or any other way around. But you can always show the navigation bar with the following workaround way:

Rather than presenting that view controller modally present a navigation controller modally with its root view controller set as the view controller you want:

MyViewController *myViewController = [[MyViewController alloc] initWithNibName:nil bundle:nil];
UINavigationController *navigationController = 
    [[UINavigationController alloc] initWithRootViewController:myViewController];

//now present this navigation controller modally 
[self presentViewController:navigationController
                   animated:YES
                   completion:^{

                        }];

You should see a navigation bar when your view is presented modally.

Ios – Best practices for Storyboard login screen, handling clearing of data upon logout

Your storyboard should look like this

In your appDelegate.m inside your didFinishLaunchingWithOptions

//authenticatedUser: check from NSUserDefaults User credential if its present then set your navigation flow accordingly

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;
}

In SignUpViewController.m file

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

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

In file MyTabThreeViewController.m

- (IBAction)actionLogout:(id)sender {

    // Delete User credential from NSUserDefaults and other data related to user

    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;

}

Swift 4 Version

didFinishLaunchingWithOptions in app delegate assuming your initial view controller is the signed in TabbarController.

if Auth.auth().currentUser == nil {
        let rootController = UIStoryboard(name: "Main", bundle: Bundle.main).instantiateViewController(withIdentifier: "WelcomeNavigation")
        self.window?.rootViewController = rootController
    }

    return true

In Sign up view controller:

@IBAction func actionSignup(_ sender: Any) {
let appDelegateTemp = UIApplication.shared.delegate as? AppDelegate
appDelegateTemp?.window?.rootViewController = UIStoryboard(name: "Main", bundle: Bundle.main).instantiateInitialViewController()
}

MyTabThreeViewController

 //Remove user credentials
guard let appDel = UIApplication.shared.delegate as? AppDelegate else { return }
        let rootController = UIStoryboard(name: "Main", bundle: Bundle.main).instantiateViewController(withIdentifier: "WelcomeNavigation")
        appDel.window?.rootViewController = rootController

Best Answer

Related Solutions

Ios – presentViewController and displaying navigation bar

Ios – Best practices for Storyboard login screen, handling clearing of data upon logout

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