how to display various view controllers (each having its respective navigation controller) using storyboard ID - objective-c

Question

I'm working on my first app. Here's what I want to accomplish:
There will be a menu with several different options. For simplicity, assume this is comprised of UIButtons with IBAction outlets and the functionality exists to pull up the menu at any time.
Each menu button, when pressed, should display a different navigation controller's content. If the user brings up the menu and makes a different selection, the navigation controller in which he is currently operating should not be affected; the newly selected navigation chain is displayed on top of the old, and through the menu, the user can go back to the view where he left off on the previous navigation chain at any time.
visual illustration (click for higher resolution):
Please note that there are 3 different navigation controllers/chains. The root view controller (which is also the menu in this simplified version) is not part of any of them. It will not suffice to instantiate one of the navigation chains anew when it has been previously instantiated, and here's why: if the user was on screen 3 of option 2 and then selects option 1 from the menu and then selects option 2 (again) from the menu, he should be looking at screen 3 of option 2--right where he left off; the view controller he was viewing when he previously left the navigation chain should be brought back to the top.
I can make a button instantiate and present a view controller from the storyboard if there is NOT a navigation controller:
- (IBAction)buttonPressed:(id)sender {
UIViewController *controller = [self.storyboard instantiateViewControllerWithIdentifier:#"View 2"];
[self presentViewController:controller animated:YES completion:nil];
}
However, I can't figure out how to make those two methods work with a navigation controller involved. Moreover, I'm not sure those two methods are the right choice, because I won't always want to instantiate a new view controller: when a menu button is pressed, a check should be performed to see if the view (navigation?) controller with the corresponding identifier has already been instantiated. If so, it should simply be made the top view controller.
In summary, here are my questions:
1) How should I instantiate and display a view controller that is embedded in a navigation controller, preferably using a storyboard ID? Do you use the storyboard ID of the navigation controller or of the view controller?
2) How should I check whether an instance already exists? Again, should I check for an extant navigation controller or for a view controller, and what's the best method to do so?
3) If the selected navigation chain has already been instantiated and is in the stack of view controllers somewhere, what is the best method for bringing it to the top?
Thank you!!
side note -- it would be nice to know how to paste code snippets with indentation and color formatting preserved :)

Answer 1

As Rob has suggested, a tab bar controller would make a good organising principle for your design.
Add a UITabBarController to your storyboard, give it a storyboard iD. Assign each of your three sets of viewControllers ( with their respective navController) to a tab item in the tabBarController.
UITabBarController
|--> UINavigationController --> VC1 ---> VC2 -->
|--> UINavigationController --> VC1 ---> VC2 -->
|--> UINavigationController --> VC1 ---> VC2 -->
In you app delegate make a strong property to hold your tab bar controller's pointer. As the tab bar controller keeps pointers to all of it's tab items, this will take care of state for each of your sets of viewControllers. You won't have to keep separate pointers for any of them, and you can get references to them via the tabBarController's viewControllers property.
#property (strong, nonatomic) UITabBarController* tabVC;
Initialise it on startup
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
UIStoryboard storyBoard =
[UIStoryboard storyboardWithName:#"MainStoryboard_iPhone" bundle:nil];
self.tabVC = [storyBoard instantiateViewControllerWithIdentifier:#"tabVC"];
//hide the tab bar
for (UINavigationController* navController in self.tabVC.viewControllers)
[navController.viewControllers[0] setHidesBottomBarWhenPushed:YES];
return YES;
}
An alternative way to hide the tab bar is to check the "Hides bottom bar on push" box in the Attributes Inspector for each of the (initial) viewControllers. You don't have to do this for subsequent viewControllers, just the first one that will be seen in that tab item.
Then when you need to navigate to one of your navController groups…
- (IBAction)openTab:(UIButton*)sender {
AppDelegate* appDelegate =
(AppDelegate*)[[UIApplication sharedApplication] delegate];
if ([sender.titleLabel.text isEqualToString: #"Option 1"]) {
appDelegate.tabVC.selectedIndex = 0;
}else if ([sender.titleLabel.text isEqualToString: #"Option 2"]){
appDelegate.tabVC.selectedIndex = 1;
}else if ([sender.titleLabel.text isEqualToString: #"Option 3"]){
appDelegate.tabVC.selectedIndex = 2;
}
[self presentViewController:appDelegate.tabVC
animated:YES completion:nil];
}
(this example uses presentViewController, your app design may navigate this in other ways…)
update
If you want to do this without a tab bar controller, you can instantiate an array holding pointers to each of your nav controllers instead:
UINavigationController* ncA =
[storyboard instantiateViewControllerWithIdentifier:#"NCA"];
UINavigationController* ncB =
[storyboard instantiateViewControllerWithIdentifier:#"NCB"];
UINavigationController* ncC =
[storyboard instantiateViewControllerWithIdentifier:#"NCC"];
self.ncArray = #[ncA,ncB,ncC];
Which has the benefit of not having a tab bar to hide…
Then your selection looks like…
- (IBAction)openNav:(UIButton*)sender {
AppDelegate* appDelegate =
(AppDelegate*)[[UIApplication sharedApplication] delegate];
int idx = 0;
if ([sender.titleLabel.text isEqualToString: #"option 1"]) {
idx = 0;
}else if ([sender.titleLabel.text isEqualToString: #"option 2"]){
idx = 1;
}else if ([sender.titleLabel.text isEqualToString: #"option 3"]){
idx = 2;
}
[self presentViewController:appDelegate.ncArray[idx]
animated:YES completion:nil];
}

Answer 2

1 / You can instantiate a viewController in your viewDidLoad method of your main viewController, so it will be instantiate 1 time only.
Now if you want display your controller, you would better push it :
- (IBAction)buttonPressed:(id)sender {
// Declare your controller in your .h file and do :
controller = [self.storyboard instantiateViewControllerWithIdentifier:#"View 2"];
// Note you can move this line in the viewDidLoad method to be called only 1 time
// Then do not use :
// [self presentViewController:controller animated:YES completion:nil];
// Better to use :
[self.navigationController pushViewController:controller animated:YES];
}
2 / I'm not sure, but if you want to check if an instance already exist just check :
if (controller) {
// Some stuff here
} // I think this checks if controller is initiated.
3 / I know it's not a good advice but I would tell you to not worry about checking if your controller already exist, because I think it's easier to access your viewController by using the 2 lines again :
controller = [self.storyboard instantiateViewControllerWithIdentifier:#"View 2"];
[self.navigationController pushViewController:controller animated:YES];
4 / I'm not sure if colors can be used here because of a specific style sheets.
I'm not sure to really have the good answer to your question but I hope this will help you.